An overview of the state of laser research in life sciences in the International Laser Center as well as in a number of research centers of the former Soviet Union is presented. Recent results are described in more detail on the following topics: (1) vibrational spectroscopy of biomolecules (including CARS and time-resolved studies); (2) time-resolved fluorescence spectroscopy of light-induced enzyme-substrate conformational dynamics; (3) photodynamical studies based on light scattering from cells and tissues; (4) computer simulation and theoretical studies of biomolecules; (5) optics and spectroscopy of chiral biomolecules.

Electron spin resonance (ODMR) experiments via fluorescence excitation spectroscopy on single pentacence molecules in p-terphenyl crystals provide information on spectral jump and temperature dependent dephasing processes. It turns out that ODMR transitions in the excited triplet and optical transitions in the excited singlet state are decoupled from each other in a way that different mechanisms determine the respective spectral behavior.

The mechanisms of cellular uptake of the photosensitizers chlorin e₆, chlorin e₆ trimethylester and chlorin e₆ ethylendiamid are reported in this paper. Each photosensitizer cellular uptake mechanism was determined by preferentially inhibiting the process of low-density lipoprotein (LDL) binding to cells and endocytosis by chilling cellular cultures or by the action of metabolic inhibitors or heparin. The results indicate that delivery with LDL plays a significant role in the process of pigment accumulation by tumor cells. At the same time chlorin e₆ derivatives uptake is only partly mediated by receptor dependence endocytosis of LDL. The involvement of molecular diffusion exchange into the binding of apolar chlorin e₆ derivatives to cells is suggested.

Photodynamic therapy (PDT) of cancer is an intensively developing modality of cancer treatment based on the phototoxic action of some dyes retained selectively in tumor tissues. One of the final goals of the studies of fundamental mechanism of PDT is the rational choice of the photosensitizer (PS). To be able to do this one should understand the basic relationship between the structure of the sensitizing molecule and the efficiency of the selective photodynamic damage eventually induced in tumorous tissues by the combined action of the PS and light. Among the variety of physico-chemical factors influencing the photodynamic processes at the cellular level we have chosen the value of pH that is important both as a microenvironmental characteristic and as a parameter of cell physiology during the process of the photodynamically induced cell death. The data reported in this paper concern both roles of pH: pH as a microenvironmental factor influencing the state of the sensitizing molecule, and cytoplasmic pH as a factor relevant for the ability of the cell to resist photodynamic action. As the sensitizer one of the second generation PS was chosen -- tetrasulfonated aluminum phthalocyanine (AlPcS₄). The experimental technique used included stationary and time- resolved fluorescence spectroscopy and microfluorometry, numerical spectra deconvolution absorption spectroscopy and pH microphotometry of single cells.

During the last decade a new modality of cancer treatment appeared, called photodynamic therapy (PDT). This treatment is based on the following observation. Some dyes, administered intravenously, are preferentially retained in solid tumors as a result of as yet incompletely understood properties of malignant tissue. Subsequent exposure to light of a wavelength that is absorbed by the dye initiates a chain of events that ends in tumor necrosis. Recent results have demonstrated the considerable potential of phthalocyanines. The sulfonated derivatives of phthalocyanine metal complexes (MeS_nPc) have been proposed for the photodynamic therapy since they demonstrate good efficiency of phototoxicity, are water-soluble and have a low level of dark toxicity. It was already reported that the sulfonation degree influences the photodynamic activity of MeS_nPc³. The present work was undertaken to investigate some parameters that determine the photodynamic effect for aluminum phthalocyanines with different degree of sulfonation.

Unusual absorption and photophysical properties are revealed for a novel fixed-distance symmetric ethylene-bridged porphyrin dimer, trans-1,2-bis(meso-octaethylporphyrinyl)ethene (tbis equals OEP in short), investigated by the methods of absorption and fluorescence steady- state spectroscopies as well as picosecond fluorescence and femtosecond transient absorption time-resolved spectroscopies. It is found that in solutions of organic solvents, tbis equals OEP exists in two isomeric forms: an isomer P, and an isomer U (ca. 85% and 15%, respectively, in toluene). It was found that lifetimes of the lowest excited singlet states of both isomers are strongly dependent on solvent viscosity, the isomer U displaying the stronger dependence. Particularly, the fluorescence lifetime of the isomer U was found to increase to approximately 0.5 ns in polymer films at room temperature or in rigid glasses of organic solvents at 77 K. To the best of our knowledge, this is the first example of such viscosity-dependent photophysics for porphyrins. A qualitative explanation of these observations is proposed.

The interaction of the therapeutic active haematoporphyrin derivatives (HpD, Photosan) with micelles, liposomes, erythrocyte ghosts and erythrocytes has been investigated by fluorescence and difference absorption spectroscopy. HpD samples of different preparations were used and exhibit similar interaction patterns with membranes. The results obtained show that the monomers and/or aggregates from the aqueous phase, which are in equilibrium with the monomers, are taken up by the membranes to a much lesser extent than chemically bound oligomers and self associated oligomer complexes. Oligomers are taken up and defolded, leading to an increasing amount of monomers in the membrane versus incubation time. The photodynamic activity during the incubation process was measured to be proportional to the fluorescence of the membrane associated monomers.

Hematoporphyrins and related species used in photosensitized tumor therapy (PTT) were revealed to be mixtures of monomers, dimers and aggregates. In this paper we present steady state and time-resolved absorption spectroscopy data about the structure of hematoporphyrins aggregates, and energy relaxation pathways of individual components of a complex mixture of different aggregated species. The activity of hematoporphyrin derivative (HpD) and dimethoxyhematoporphyrin (DMHp) in PTT was studied. Antitumor efficiency of HpD and DMHp in PTT is similar, but HpD expresses better therapeutic effect, and it is probably due to the positive influence of covalently linked structures present in the solutions of HpD on the organisms.

Optical line shapes were calculated for photosynthetic light-harvesting complexes using general formalism of exciton-phonon interaction in molecular crystals. We analyzed the quasi one-dimensional molecular systems such as circular bacteriochlorophyll (BChl) aggregates (LH1 and LH2 complexes of purple bacteria). The theory is valid for arbitrary strong linear electron-phonon coupling covering the delocalized (free) exciton as well as localized (self- trapped) exciton limits. The theory is used to analyze the recent hole-burning data on the light- harvesting antennae of purple bacteria.

The modified electro-optical absorption and emission methods are described as well as their use for measurements of electrical dipole moments of five aminophthalimides (APs) in ground and excited states. It is found that there exists a principal difference between properties of 3- aminophthalimide (3AP) and 4-amino-N-methylphthalimide (4ANMP) in different solvents. The equilibrated dipole moment of 3AP in its excited state is practically independent on the solvent polarity, in comparison with 4ANMP.

Excited electronic states of Zn-porphyrin (pi) -radical anions are studied by methods of picosecond absorption spectroscopy and quantum chemistry. An optical absorption spectrum of Zn-octaethylporphin (pi) -radical anions in its lowest excited doublet D₁ state is obtained experimentally. Excited states energies are calculated by CNDO/S-CI method. Two allowed transitions from the D₁ state are found in calculated spectrum. These theoretical data agree with the experimental spectrum which exhibits two absorption bands at ca. 500 and ca. 600 nm.

It is well known that methanol and ethanol at low concentrations associate with ferrihemoglobin and ferrimyoglobin to form complexes in which the alcohol groups are bound directly to the ferric ions. The nature of the complexes [heme iron-alcohol ligand] and their relations to the function of hemoprotein molecules have not been satisfactorily explained so far. Octaethylporphynatoiron complexes (Fe-OEP), taking into account their molecular structure, are often used as model systems for studies of heme properties. Ogura et. al., while investigating the photoreduction mechanism of Fe(III)-OEP complex with 2- methylimidazole in dichloromethane (CH₂Cl₂) solution by resonance Raman and absorption spectroscopies, have found that a trace amount of alcohol present in CH₂Cl₂ as a stabilizer can initiate the photoreduction process. An unexpected finding in this study was the observation that laser irradiation into the CT band at 585 nm didn't induce the photoreduction. Recently we observed the same photoreduction process, when the starting materials were alkoxocomplexes of Fe-OEP [Fe(OR)-OEP, were R equals CH₃, C₂H₅]. This paper contains new data regarding the structure, spectroscopic, photochemical and photophysical properties of the photoactive products, generated in the reactions of Fe(III)-porphyrins with alcohols.

Fragment method was used to carry out quantum chemical calculations on the Mg porphin dimers placed in a uniform electric field (epsilon) . For the two structures considered, of the D_4h and D_4d symmetry, the field lay in the C₄ axis; its magnitude was varied from 0.0005 to 0.1 a.u. It has been shown that the action of the electric field causes qualitative changes in the structure of the excited states of the dimers. In particular, the forbidden component of the Q state effectively mixes with the charge transfer states and at (epsilon) > 0.0025 a.u. the charge transfer level is the lowest excited one.

Supramolecular ensembles stable at room temperature (complexation constant and activation energy range from 5 (DOT) 10⁶ M^-1 to 5 (DOT) 10⁷ M^-1 and from 0.5 to 1.0 eV correspondingly) containing up to five macrocyclic fragments have been constructed using two-fold ligation of Zn-porphyrin and Zn-chlorin chemical dimers by pyridyl substituted porphyrin or related molecules. Spectral, photophysical and thermodynamic properties of triadic and pentadic arrays have been studied in a temperature range from 140 to 360 K. Kinetic behavior of the complexes was investigated using a fluorescent picosecond laser setup ((Delta) t approximately equals 30 ps) with 2-D (wavelength-lifetime) registration. Observed spectral properties are explained in terms of extra-ligation (red shift of all electronic bands <EQ 550 cm-1)) and excitonic splitting ((Delta) E < 1900 cm^-1). Nonradiative for- and backward excitation energy transfer (K > 10¹⁰ c^-1), electron transfer and d-(pi) interactions are discussed as the main paths of electronic excitation deactivation in the complexes.

Fluorescence spectrum of flavin adenine dinucleotide adsorbed on the silver electrode was obtained. Dependences of the fluorescence intensity and the surface enhanced Raman scattering intensity on the electrode potential were similar. It was found that the 1,3,5- threephenil pyrasole molecules adsorbed on silver island films (SIF) undergo photo- transformation at a radiation with 458 nm. The products of this transformation have got an intensive fluorescence in the range from 500 to 600 nm. It was found too the surface enhanced fluorescence of 2,6-TNS bound with human serum albumin adsorbed on SIF.

The process of the phytochrome phototransformation from red to far red form in water solution and polyacryilamide gel matrix has been investigated by the laser flash photolysis method. It was shown that the native phytochrome insertion into the polyacrylamide gel matrix leads to the decrease of rate of meta-R_c intermediate decay and second component of lumi-R decay.

One of the most interesting problems of modern biophysics is the problem of enzyme conformational changes during the catalytic act. There are some bands in the vibrational spectra of proteins that may be sensitive to the conformational state of the macromolecule. The aim of the present study is to reveal the changes in protein vibrational spectra associated with the interaction with the substrate by means of highly sensitive PSCARS spectroscopy and to refer these spectroscopic changes to the possible conformations of the protein molecule. The peculiarities of the experimental method applied are associated mainly with a very high nonresonant background to resonant signal ratio. This makes necessary the polarization suppression of the background, the sufficient quality of which may only be achieved with very high polarization quality of the pumping beams and rather thin samples (about 2 mm). The PSCARS spectra were measured of protein chymotrypsin and its complex with antranilic acid (model of substrate in this system) solutions in water and heavy water. The spectra were obtained within three frequency ranges: 800 - 900 cm^-1, 1180 - 1300 cm^-1, 1580 - 1700 cm^-1. The vibrational bands analyzed were amide I, amide III, and several bands belonging to tyrosine and tryptophan. It was demonstrated that all the bands studied were sensitive to the ligand binding. The fitting procedure was applied to all the PSCARS spectra and the vibrational bands' parameters were determined (positions, bandwidths, amplitudes). Hereafter we present some details on the results obtained for amide I band.

Vibrational sum-frequency (SF) spectroscopy is a nonlinear optical technique which is highly surface sensitive and therefore very well suited for investigating molecular monolayers adsorbed on liquid and solid surfaces. We studied long chain fatty alcohols and amines physisorbed at the interface liquid/air and of octadecyltrichlorsilan (OTS) chemisorbed on glass in situ, i.e., in normal laboratory environment. Information on the molecular conformation and orientation is obtained from the SF spectra. The amplitudes of the degenerate methyl stretching mode for different polarization combinations of the incident and radiated fields is used to determine the molecular orientation with increased accuracy. Varying the pH-value of the aqueous subphase of a Langmuir film formed by octadecylamin, characteristic changes in the CH- and NH-spectral region are observed. The occurrence of CH₂-resonances indicates conformational deformations dependent on bulk pH. In this way SF spectroscopy is demonstrated to be an independent method for determining the surface pK of surfactants. Chemisorbed films of OTS have been prepared by polymerization of OTS on a glass substrate in anhydrous solution. Vanishing CH₂-resonances indicate straight chains of the adsorbed molecules, whereas from the line strength of residual Si-OH vibrations information on the degree of polymerization may be obtained.

Resonance Raman studies of simple peptides have provided a new view of the electronic excitations of these important chromophores. The large effect of isotropic substitution and of hydrogen bonding on resonance Raman spectra provide a new method for testing theoretical calculations. These calculations can be refined by direct comparison of theory with experiment and also used to evaluate the likelihood that further experiments will provide interesting new information. Our recent work has shown how fruitful this cyclic interaction can be. In this on going exploration we are developing experimental methods and testing theoretical descriptions of the electronic excitations of peptides and related ultraviolet chromophores of proteins in solution. The specific areas of interest are (1) examination of the effect of hydrogen bonding on the electronic excitation of peptides; (2) evaluation of the effects of fluctuations in solvation on the electronic excitations of peptides; and (3) studies of the n(pi) * and higher energy electronic excitations of peptides predicted by theory and potentially important in the description of circular dichroism.

Raman spectroscopic techniques are developed to study the presence, structure and dynamics of (bio-)organic molecules at surfaces. Coherent anti-Stokes Raman scattering (CARS) and spontaneous Raman scattering (spRS) are used in combination with the technology to fabricate optical waveguides. A mode-locked Nd-YLF laser system with approximately 8 ps. pulse lengths was used as well as a Q-switched nanosecond pulselength Nd-YAG laser. In principle the spRS technique is more simple, however the CARS technique allows background suppression by asymmetric mode selection. Improvement of the ratio of signal of the monolayer to that of the waveguide can hence be expected. A theory was developed that describes the radiative field of a dipole in a waveguide. This theory describes the angular distribution of the radiated power from a dipole positioned at a chosen position in the waveguide configuration. It is calculated that the power varies strongly as a function of direction of observation. In particular in the direction where coupling into substrate modes occurs this is predicted to be the case. The intensity of the Raman scattering in well defined directions can be an order of magnitude larger than in the average direction.

Due to the coherent nature of the third order CARS process the spectra obtained are often seriously corrupted by the noise brought by the laser pulse-to-pulse fluctuations. A broadband (multiplex) CARS technique is known to be an efficient mean to diminish the noise contributed by the laser power fluctuations as well as the imperfections in the spatial and temporal coherence of laser beams. In this work, we coupled the broadband CARS scheme with the `scanning-multichannel' detection technique. By combining several multichannel Raman spectra detected by a CCD camera at different positions of a monochromator, the authors have achieved (1) enhanced dynamic range, (2) large spectral length, (3) improved accuracy of peak position and bandwidth determination due to an increased density of measurement points and (4) elimination of the variation in the sensitivity and noise characteristics of each detector element.

New possibilities for the resolution of Raman bands, provided by polarization sensitive CARS in combination with a phase-mismatching technique, are presented. It is shown that the variation of the wave mismatching and the ratio of windows thickness makes obtaining the additional information about close Raman resonances possible.

We report polarization sensitive coherent Stokes Raman scattering (CSRS) measurements of oxy- and deoxyhemoglobin in aqueous solutions that were carried out under electronic resonance with the Q absorption bands. All independent susceptibility (Chi) ⁽³) components as well as anisotropic and anti-symmetric scattering contributions were resolved within frequency nondegenerate CSRS scheme. Eight bands of oxy- and five of deoxyhemoglobin were observed in the range 1500 - 1680 cm^-1. Each set of dispersion profiles was simultaneously fitted with a set of parameters including band positions, widths, amplitudes, phases and, importantly, all the CSRS depolarization ratios. On this basis the major bands were assigned to non-totally symmetric (nu) ₁₀, (nu) ₁₁, and (nu) ₁₉ modes of the porphyrin macrocycle. These displayed a clear correlation of vibrational phase with the mode symmetry. Of eight bands resolved in oxyHb spectra three were attributed to features of intermediate deoxyHb, caused by a partial photolysis of oxyhemes. On a nanosecond time scale they were found essentially similar to those found for stable deoxyHb. A detectable isotropy was observed for all non-totally symmetric modes of both oxy- and deoxyhemes. The (nu) ₁₀ and (nu) ₁₁ modes were found to exhibit anti-symmetry as well. The decrease in depolarization ratio (rho) ₁₂₁₂^R of anomalously polarized (nu) ₁₉ mode from 7.7 (oxyheme) to 4.3 (deoxyheme) was detected. The latter evidenced heme deformation related with a further doming that occurs upon release of oxygen.

The theory of RSRS in a multi-mode pump field with a symmetric spectrum is developed. The spectral dependences of a RSRS-gain coefficient for the different values of distance between modes and amplitudes of pump modes are studied. The conditions of an arising of narrow resonances with width approximately (gamma) are defined.

The SERS spectra of alcohol oxidase purified from Pichia Pastoris and Candida Boidinii adsorbed on silver electrode were obtained. The effect of stabilization of protein by NaN₃ was studied by SERS of flavin adenine dinucleitide released from flavoprotein near the Ag surface. The dissociation of falvin from flavoprotein in N3-anion from and in neutral form independence on functional state of protein has been supposed. The association of protein oligomers and the peculiarities of quaternary structure are discussed as a reason of different SERS behavior of alcohol oxidase from various different sources.

The application is discussed of saturation resonance Raman technique with nanosecond lasers both in spontaneous and coherent regimes to the investigations of the excited states of metalloporphyrins. It is shown that saturation technique enables us to obtain new information about transient states, additional to the data of direct kinetic measurements. For nickel octaethylporphyrin (OEP) complex, we present spectroscopic evidences for the population of the higher excited electronic state, presumably of the ¹B_1g origin. For CuOEP dissolved in a number of oxygen (O)-containing solvents, the existence of fast channel of relaxation via the excited charge-transfer (CT) state is also proven on the basis of saturation Raman data. To explain the observed transformations in transient Raman spectra under variation of excitation power, simulations of the population redistribution processes in both systems are performed using quasi-stationary rate equations approach. The advantages of resonance coherent anti-Stokes Raman scattering (RCARS) over spontaneous resonance Raman (RR) spectroscopy is proven unambiguously in such type of investigations.

Interferometric coherent anti-Stokes Raman scattering (ICARS) using non-transform-limited broadband ns-dye lasers is used for time-resolved measurements of vibrational frequency and dephasing time of solutions of bis-(dimethylamino)heptamethinium iodide and all-trans- (beta) -carotene. The results are compared with those obtainable from conventional narrowband scanning CARS. The intensity of the strongest Raman lines of all-trans-(beta) - carotene (1523 cm^-1 and 1153 cm^-1) decrease for a Stokes laser power density exceeding 1 GW/cm² ((lambda) approximately equals 550 nm). ICARS reveals a simultaneous broadening of the 1523 cm^-1 line from 11 cm^-1 to 25 cm^-1.

Polymethine dyes and its derivatives are attractive for their interesting optical and photo- electric properties. In the case of a polymethine which does not isomerize we were able to show by means of time-resolved absorption spectroscopy that the singlet state photoelectron transfer to methyl- and benzylviologen had an efficiency of 0.15 with rate constants of 6.7 (DOT) 10⁹ and 4.6 (DOT) 10⁹ l/mole(DOT)s, respectively, yielding the polymethine dication radical. The photo-reduction with tetraphenylborate and potassium rhodanide is also very efficient with an efficiency of about 0.10 with rate constants of 2.4 (DOT) 10¹⁰ and 1.6 (DOT) 10¹⁰ l/mole(DOT)s, respectively, yielding the polymethine neutral radical. The spectral differences of the observed radical spectra are small. The investigation of the temperature dependence of the photo induced electron transfer of the investigated polymethine to methylviologen results in an activation energy (Delta) G* equals 24 kJ/mole and a value of the frequency factor of A equals 4.7 (DOT) 10¹⁴ l/mole(DOT)s. Strong deviation from a linear Arrhenius plot was observed at low temperatures which can be explained by solvent-solute interaction decreasing the electron transfer rate constant at lower temperatures. The calculated electron transfer rate constants agree with the assumption of the investigated process as a diffusion-controlled one. We have investigated the time and spectral evolution of the energy transfer process from a polymethine dye to different energy acceptor dyes in solution as well as in Langmuir-Blodgett layers. The general question within this respect was the involvement of an intermediate electron transfer as competitive process in the energy transfer process.

The process of the oxygen photodissociation and rebinding with human hemoglobin have been studied by the time-resolved absorption spectroscopy. The primary quantum yield (gamma) _o does not depend on the pH and its estimated value is 0.3 +/- 0.1. The apparent quantum yield (gamma) corresponding to the portion of O₂ molecules which escape from the protein to the solvent depends on the pH. It has been shown that the entrance and exit of the oxygen molecules into/from the globin matrix is controlled by the same Bohr residues. The pK values were calculated and the attribution was made. The unusual behavior of the oxygenation parameters at pH > 8.5 was observed and explained by the action of the (alpha) 140-Tyr and (beta) 145-Tyr. The picosecond ligand rebinding dynamics were measured and the phenomenon of the pK value change was studied. It was explained by the subunit tertiary structure relaxation in terms of the transition between deoxy-R- and oxy-R- structures of the tetramer protein.

We have used approximately 40 fs pulses from a Ti:sapphire laser to investigate the ultrafast energy transfer and relaxation dynamics in the light-harvesting pigment-proteins of photosynthetic purple bacteria. Our results reveal two new features, not earlier observed in light-harvesting pigments: (1) ultrafast relaxation characterized by a time constant of approximately 20 fs, which we interpret as interexciton state relaxation; (2) coherent nuclear motions. These new results are challenging the applicability of the `standard' Forster theory to the excitation transfer in photosynthetic antennae which motivated us to examine a more detailed description of the dynamics.

We report the results of our femtosecond laser study of the photophysical and photochemical properties of the DCM styrenic dye. Our femtosecond pump-probe experiments using a white light continuum show a red shift of the gain spectrum and a blue shift of the S₁ yields S_n absorption band due to a fast reorganization of the solvent cage around the highly polar fluorescent first singlet excited state. There is no evidence of any locally excited (LE) to twisted intramolecular charge transfer (TICT) state transition.

Excited-state dynamics of water-soluble Cu-5,10,15,20-tetrakis[4-(N- methylpyridyl)]porphyrin(Cu(TMpy-P4)) groove-bounded to poly(dA-dT) or dissolved in neat water phosphate buffer were investigated. In the first case, double-exponential decay kinetics were found with time constants of 35 +/- 7 ps and 3.2 +/- 0.5 ns. Spectral features of the transient absorption, a comparison with photophysical properties of CuP in oxygen-containing solvents as well as earlier RR investigations of an exciplex formation between Cu(TMpy-P4) and some polynucleotides enable us to attribute the two observed transient species to the triplet ^2,4T₁ state of four-coordinate Cu(TMpy-P4) and to the (d,d) state of five-coordinate Cu(TMpy-P4) axial liganded by CO group of thymine residue, respectively. In the case of Cu(TMpy-P4) in neat phosphate buffer, double-exponential kinetics of a transient species depopulation was observed with time constants of 21 +/- 3 ps and > 2 ns. Spectral feature of the transient absorption enables us to attribute the first transient species to the triplet ^2,4T₁ state. We believe, the reason of such short ^2,4T₁ state lifetime is liganding of the excited Cu(TMpy-P4) by molecules of H₂O resulting in deactivation via downshifted CT state and/or (d,d) state. The second transient species corresponds, most likely, to the (d,d) state.

The photophysical properties of some new and also some known complex organic molecules emission and generated radiations in the wavelength interval 340 - 560 nm have been studied in a wide range of organic solvent. Specifically, these molecules are based on phenyl, furyl-, thienyl-oxazoles and oxadiazoles to compile a quasihomological series. Using the measured values of the extinction (epsilon_abs^(nu )), the fluorescence quantum yields ((gamma) ), and the fluorescence lifetime ((tau) ), we calculated rate constants for radiative decay (K_fl), and intercombination conversion (K_ST), along with the cross sections for absorption ((sigma) ₁₃^max), and stimulated emission ((sigma) ₃₁^osc). We also found the longest pump-pulse rise time (t_lp) for which generate of oscillations active molecules. A broad spectrum of singlet and triplet electronic states using the semiempirical SCF MO LCAO method (Parr-Pariser-Pople, PPP/CI, a model approximation of (pi) - electrons) and the complete and incomplete neglecting of differential overlap (CNDO/S-CI and INDO/S-CI, sp-electronic basis). In this paper, the photophysical parameters (gamma) , (tau) , (sigma) ₃₁^osc, (sigma) _3S^*, (sigma) _2T^*, t_lp, K_fl, K_ST, E_lp (the threshold of the pump energy density) in the quasi-gomologicals series of complex active molecules are treated as depending on the structural factors in different ways. The physical mechanism responsible for the improvement in the photophysical properties of the mono-, three- and pentacyclic phenyl-, furyl-, and thienylbisoxazoles and oxadiazoles is established. The improvement is observed in the case when the separation of the bands of emission ((sigma) ₃₁^osc) and induced absorption on the S₁^* yields S_n^* ((sigma) _3S^*) and T₁ yields T_n ((sigma) _2T^*) transitions is maximum.

We investigate the spectroscopic and photophysical properties of new series complex molecules, which is capable of fluorescence and some generating light in solvents of various kinds within the wavelength region 308 - 420 nm with a high fluorescence quantum yield (gamma) equals 0.01 - 0.97 and a low threshold pump density E_lp(P_lp). We worked from the measured lifetimes and to calculate the rate constants for radiative decay (K_fl) and intercombinational conversion, (K_ST), the cross section for a stimulated emission ((sigma) ₃₁^osc), and the characteristic time t_lp in solvents of various types and in the vapor. The latter is the limiting rise time of the pump pulse (t_lp) at which the generation of electromagnetic radiation is still possible. The cross sections for the induced singlet-singlet ((sigma) _3S^*) and triplet-triplet ((sigma) _2T^*) absorption in the generation band, required for calculating t_lp, were taken from a variety of sources: experimental and for all other complex molecules, we used results calculated by some semiempirical methods SCF MO LKAO the Pariser-Parr-Pople (PPP/CI) and in complete neglect of differential overlap (INDO/S-CI). The results show that the decrease or increase of in the switch from solution to vapor, or as the properties of the solvent change, stems from dynamic separation or overlap of the lasing and induced absorption bands of the S₁^* yields S_n^* and T₁ yields T_n transitions. Lasing does not occur in concentrated acids because of the nearly complete overlap of the limiting gain and induced absorption T₁ yields T_n transitions (compare it with the behavior of dyes in their chemo absorbed state). Using the density matrix method, we show that the solvent affects the distribution of electron density among the individual atoms and fragments of the complex geteratomic molecule in the ground state, leading to systematic changes in geometry. As a result, there are changes in the distribution of bond lengths in the rings of the azo-cycles aromatic molecule. Photonation of the nitrogen atoms in the azocycles molecules changes the structure of the excited electronic singlet (S_i^*) and (T_i) triplet states and in the transitions S_O yields S_n^*, S₁^* yields S₀, S₁^* yields S_n^*, T₁ yields T_n, T₁ yields S₀, which determine the spectroscopic and generation characteristics of the complex compounds. The calculated geometry vapor complex molecules and [(sigma) (pi) ]-anion and [(sigma) (pi) ]-kation radicals compound AM-1/CI and PPP/CI methods in the ground state in their chemosorbtion state of the surface.

The application of two-color incoherent cross-correlation spectroscopy to study ultrafast processes in organic liquids and solutions is discussed. This kind of time-resolved spectroscopy is based on using two broadband correlated pulses of long duration with different central frequencies. Its time resolution is determined by the cross-correlation time of the intensities of used radiations. The statistical properties of the radiations have been investigated. The developed technique allowed us to perform kinetic measurements with femtosecond resolution on the ordinary nanosecond laser spectrometer modifying it in a comparatively simple way. The present technique was demonstrated and tested by studying subpicosecond Kerr dynamics in a number of organic liquids and their mixtures. An approach is also proposed to study the population relaxation of electronic and vibronic states of organic molecules including non-luminescent ones.

The torsion constants of both linear and circular forms of the same approximately 200 base- pair DNA were measured by time-resolved fluorescence polarization anisotropy (FPA). Upon circularization, the torsion constant undergoes a substantial increase, and the circular dichroism (CD) spectrum indicates a significant perturbation of the secondary structure. The torsion constant of the circular form lies in the range of values determined previously for similarly small circular DNAs by static methods. It is suggested that the long-standing discrepancy between torsion constants obtained via static methods for small circles and those obtained via the FPA method for linear DNAs may be due to such an alteration of the secondary structure and enhancement of the torsion constant by coherent bending strain present in the small circles.

In this work we present a general approach in the theory of nonlinear spectroscopic ellipsometry (NSE) that is based on a very powerful and compact tensor operator formalism. Using such a theoretical treatment, we propose novel nonlinear spectroscopic techniques. The validity of our theoretical predictions is supported by the experimental results.

Based on studies of polarization-state-dependent self-action of a laser pulse in a nonlinear optically active liquid, a method is proposed for determining the possible difference of the orientational relaxation times of the intensity-dependent parts of the refractive indices for different circularly polarized waves.

This article contains the theoretical description of waves' propagation in an isotropic noncentrosymmetric slightly nonlinear and slightly absorbing medium with weak spatial dispersion in noncolinear interaction scheme. The calculations were carried out by expansion on normal waves. The self-action of a powerful wave and its influence on the weak wave were taken into account. The equations describing the double frequency generation process at nonlinear wave interaction were derived by the slowly varying amplitudes method. These equations were analyzed up to first-order infinitesimal precision. The powerful wave and the weak one generate the complicated interference field, so that the amplitude of a double frequency wave has the complex spatial distribution by transverse coordinates, which depends on the wave's and frequency's disparities. The angular spectrum of the double frequency wave has been analyzed.

New spectroscopic schemes studying noncentrosymmetrical media (nonracemic solutions of chiral molecules) are based on investigation of frequency dispersion of the fourth-order dipole susceptibility tensor (chi) _ijklm⁽⁴D)((omega) _a;(omega) ₁,(omega) ₁,(omega) ₁,-(omega) ₂). This paper contains the accurate quantum-mechanical calculations of the resonance part of hyper-polarizability tensor (gamma) '⁽⁴D) and its connection with Raman ((alpha) '⁽²) and hyper-Raman ((beta) '⁽³)) scattering tensors. In the case it was suggested pump frequencies' combination (omega) ₁ - (omega) ₂ scanning one of the vibrational resonance of the molecule: (omega) ₁ - (omega) ₂ approximately equals (Omega) . Tensor (gamma) '⁽⁴D) was averaged over arbitrary orientations of noncentrosymmetrical molecules in the solution by applying irreducible tensors operators' technique giving dipole susceptibility tensor (chi) '⁽⁴D) equals NL⁴<(gamma) '⁽⁴D)>. Symmetry of this tensor coincides with the model calculations. As it was expected, tensor (chi) _ijklm⁽⁴D)((omega) _a;(omega) ₁,(omega) ₁,(omega) ₁,-(omega) ₂) includes only 6 non zero components equal by their absolute values. For centrosymmetrical molecules in isotropic medium tensor (chi) '⁽⁴D) is equal to zero. Similar computations were made in the hyper-Raman resonance case 2(omega) ₁ - (omega) ₂ approximately equals (Omega) .

Various frequency-domain and quasi-elastic scattering methods and techniques which are prospective for biological tissues spectroscopy and imaging are discussed. Methods under investigation are characterized by the wide frequency range of diffusing light intensity modulation from Hertz up to gigahertz, by harmonic or random light intensity modulation produced by light source modulators, tissue movements, and light beam scanning.

The possibilities are proposed of imaging of highly scattering objects based on the measurements of correlation characteristics of the spectrum of scattered radiation.

The dynamic light scattering (DLS) method provides us with information about the apparent diffusion coefficient, D_app, as well as the static scattering intensity, I_s. For long but thin rods with length L and diameter d (i.e., KL >> 1 but Kd << 1, K being the length of the scattering vector), the dependence on L and d of D_app is quite different from that of I_s. By means of DLS were studied synthetic myosin filaments of vertebrate skeletal muscle in solution at pH 8.3. It appeared that Mg²⁺ ions induced lengthening and thickening of the filaments whereas ATP (and ADP) induced shortening (depolymerization) of the filaments. When ATP was added to the filament preparation in the presence of Mg²⁺ ions, thinning of the filaments (or splitting into subfilaments) occurred prior to shortening (depolymerization).

The influence of the correlation between the size and electrophoretic mobility of particles on the shape of laser Doppler electrophoresis spectrum is considered. The theory of spectrum shape in the presence of such correlation is developed. It is shown that the oscillatory dependence of a light scattering cross-section of large particles on their size may distort substantially the spectrum shape corresponding solely to the electrophoretic mobility distribution in a particles system. Even the appearance of `false' line structure in the spectrum is possible for polydisperse particles systems with smooth distribution curves but with a high degree of size-electrophoretic mobility correlation. The theory explains naturally the oscillation structure observed in Doppler electrophoresis spectra of certain large cells.

Light scattering spectroscopy (LSS) was used to measure particle sizes in fresh human gallbladder bile of patients with gallstones. The recent experiments suggest the presence of a novel, bile salt-independent, mode of cholesterol transport in saturated human bile. Cholesterol is carried in large phospholipid vesicles with approximate diameter of 75 nm. It was shown that under experimental conditions these vesicles were able to dissolve up to 80% of the biliary cholesterol at low bile salt concentrations. A lecithin lamellar phase has already been suggested as a cholesterol carrier and recently vesicles were reported in model bile solutions and in native bile. Due to its nonperturbing nature, the technique of LLS has in recent years become widely applied to the study of micellar systems and, in particular, has been used to systematically investigate aqueous biliary lipid systems. LSS was employed to characterize the size, shape thermodynamics and interactions of bile salts micelle.

All 16 elements (X_ij) of phase matrix (PM) show sensitivity to changes in sizes, and shapes of erythrocite aggregates. The mean size of the aggregates was approximately 200 micrometers . Such aggregates are present in blood under many diseases, such as atherosclerosis, diabetes, etc. Blood erythrocites adhere each other by their plane surfaces to form so-called `coin columns.' PMs of whole blood samples were measured for ills directly after sampling without pre-preparation and for healthy donors. Both the common features of PM and the angular distribution of PM elements are studied for observation angles from 100 to 170 degree(s). To measure elements of phase matrix under single scattering and such a high density, we have been caused to study erythrocytes within a thin layer. Thickness of the layer was 10 micrometers . Single erythrocytes are not deformed within it, but the aggregates oriented normal to the scattering plane. The structure of measured phase matrices was influenced by this fact. Analysis of measured matrices has shown their structure does not differ for samples with extended or weak aggregation.

In the present paper speckle-interferometric technique utilizing focused Gaussian beam diffraction was applied for the analysis of lymph circulation in narrow native capillaries. The spectrum of scattered intensity fluctuations of the statistically inhomogeneous speckles formed with the diffraction in such capillaries are presented. The alterations of the spectra envelope caused by drug administration to the lymph vessel have been studied.

We consider laser radiation scattering by the diffuse skin surface. The skeletal human muscle transmitting its vibrations to the skin is thought of as a system of vibrating strings with a variable length.

The possibility of using strongly focused coherent Gaussian beams diffraction for cardiovibration measurements is considered on the basis of a numerical modeling conducted for this type of light scattering from the vibrating rough surface. The optical scheme for cardiovibration measurements is suggested. The forming of output signal of the measuring system has been studied. The region of parameters when the considered system operates in linear regime has been determined. The influence of profile statistics on investigated system output characteristics has been analyzed.

The backscattering nephelometry technique is used to simultaneously obtain the aggregation and disaggregation parameters of erythrocytes in whole blood: characteristic times T₁ of linear aggregates formation and T₂ of network formation; hydrodynamic durability of aggregates (beta) , and the coefficient of deformability of erythrocytes D. We have previously shown that these parameters are sensitive to different diseases, external conditions and stimuli. Samples of blood have different values of hematocrit H. So we have studied dependences of parameters T₁, T₂, and (beta) on suspension hematocrit. The obtained results show that the values of T₁ are inversely proportional to H² for both blood of healthy donors and blood of patients suffering hereditary glomerulonephritis. With hematocrit growing towards 100% (H equals 1) these aggregation parameters asymptotically aspire to certain values which determine the natural limit of the aggregation rate. The decrease of hematocrit causes the intensification of shear-induced aggregation at shear rates up to 150 s^-1.

The photochemistry of large molecules with conjugated (pi) -systems plays an important role in many systems of biological interest, including vision and photosynthesis. The size of these systems, however, often precludes a detailed knowledge of the electronic states and associated potential energy surfaces on which the photochemical dynamics takes place. We present some recent progress in the construction of empirical excited state potential surfaces of conjugated molecules based on an analysis of spectroscopic, ab initio, and ultrafast lifetime measurement data. These surfaces are then used to investigate the excited state dynamics of both reduced- and full-dimensionality molecular models, including nonadiabatic processes. Applications to the photoisomerizaton reactions of the model system stilbene are featured.

Quasiclassical methods for simulation of electronically excited polyatomic molecule's dynamics in pulsed laser field, which are the combinations of classical molecular dynamics method and quantum calculations of the electronic excitation, are discussed. It is argued that just three major approaches are sufficient to calculate both classical dynamics of nuclei and dynamics of the electronic transition, namely, (1) surface-hopping procedure, which describes dynamics of the transitions to the ground electronic state caused by external laser field; (2) quantum calculations of electronic transitions within a frame of potential energy surfaces harmonic approximation; and (3) calculations based on the random quantum jumps model. The first two approaches are suitable in the weak-field limit. The latter one works well in strong- field limit. Applications of the discussed approaches to stilbene photoisomerization dynamics and HCl⁺ molecule photodissociation dynamics are presented.

A two level model is considered to describe the dynamics of a biological system undergoing cyclic oscillations from one state to another separated by an energy quantum interval. This is typically met in enzyme activated reactions, involving the ADP-ATP cycle. General results can be obtained analytically, the dynamics of the system being investigated from an energetic point of view. Numerical solutions show how an enzymatic system can be driven across different regimes where cooperation (allostericity) and oscillations appears. The model can be extended to the case of an external energy supply in the form of electromagnetic radiation, providing clues for a physical understanding of nonthermal laser interaction with biosystems.

Influence of intramolecular dynamic structure on the process of energy transfer from the place of original localization to the active site and processes in the active site of enzyme is under consideration. The possibility of realization of `marked' degrees of freedom when the system motion occurs in a narrow area of phase space was considered within the framework of a simplest cluster model of an enzyme molecule. Under certain conditions the motion of the system becomes complex and perhaps stochastic and the spectrum of oscillations becomes more rich. the role of the interaction potential curve shapes of the system is discussed. Problems of spectral transformation and complexization and characteristic times determination are important for interpretation of the data obtained by the methods of laser spectroscopy and CARS, in particular. We discuss the problem of overcoming the potential energy barrier inside the active site in terms of the location and energy of definite parts of the substrate within the framework of a 2D model. The special role of fluctuations of atom groups and the substrate influence on the process are taken into account.

Light-induced 3D-structure (both stable in time and dynamic) in highly nonlinear ordered liquid with optical anisotropy are considered. The physics of discussed phenomena are determined by threshold optical non-linearity of the liquid crystals under condition of competition and energy transfer between waves with orthogonal polarizations. An intrinsic feedback for such a wave interaction, when the laser beam induces the bulk-grating of anisotropy arises because of the non-local response of the elastic medium on the external field. Dynamic scattering (diffraction) of the laser pulses (beams) on such a grating (natural or induced by external field) results in variation of their profile and makes it possible to develop the compression (squeezing) effects both in time and space.

Excitation dynamics in the light-harvesting core antenna of purple bacteria were studied theoretically using a model of excitation delocalization over the circular aggregate of strongly interacting bacteriochlorophyll molecules. Energy transfer from the core antenna complex to the reaction center (RC) and between core antenna complexes was treated as a Forster-type process. The advantages of the proposed model as compared with other models are discussed.

Our preliminary measurements of blood flow velocities in rat mesentery microvessels performed by laser Doppler microscopy have served as a basis for developing of a mathematical model describing the influence of drag-reducing polymer molecules on microcirculation. The model takes into consideration linear (Poiseuille law) and nonlinear parts of the vessel resistance. The results of modeling are in accordance with experiments and give a 1.5 ... 2.5 times decrease of nonlinear part of individual vessel resistance.

This paper presents the version of a Monte Carlo method for simulating of optical radiation propagation in biotissue and highly scattering media allowing for three-dimensional geometry of a medium and macroinhomogeneities located in one of the layers. The simulation is based on use of Green's function of medium response to single external pulse. The process of radiation propagation is studied in the area with given boundary conditions, taking into account the processes of reflection and refraction at the boundaries of layers inside the medium under study.

A mathematical model of interaction between laser radiation and multilayer biological tissue has been developed. At a pulse duration shorter than 1 ms acoustic or shock waves are generated in the tissues simultaneously with a rapid temperature rise. At radiation power densities lower than approximately 10⁹ W/cm² in the absence of phase transition acoustic vibrations arise from thermal expansion of the heated volume.

The spectral analysis of biological tissues in vivo is widely used in various fields particularly in medical diagnostics and therapy control. Great possibilities of spectral tissue analysis exist to be realized in the future. Among them are the complete non-invasive clinical blood analysis with evaluation of, for example, sugar concentration in blood; the evaluation of chemical state and localization on subcell level of various drugs binded with biological structures. These facts were shown to affect drastically the drug therapeutic activity. The main advantage of spectral analysis of tissues in vivo is its noninvasivity. This allows one to get information about tissue condition without affecting the dynamic of various biological processes. Another advantage of optical tissue analysis is the possibility to process data in real time and to control parameters of therapy process according to information acquired. For example the in situ analysis of photosensitizer concentration and its chemical state during photodynamic therapy makes it possible to correct the laser irradiation intensity (the photobleaching of photosensitizer requires the decrease in laser intensity).

A mathematical model of contact laser destruction of normal and tumor liver tissues by radiation of YAG:Nd laser is described. We present the results of the simulation of tissue heat destruction, taking into account the influence of blood and lymph circulation on the processes of heat transfer. The problem is adapted to the case of liver tissue with tumor. A liver is considered as a capillary-porous body with internal blood circulation. Heatconductivity and tissue-blood heat transfer are considered. Heat action is assumed to be implemented with contact laser scalpel. The mathematical model consists of two inhomogeneous nonlinear equations of heatconductivity with spherical symmetry. Nonstationary temperature fields of tissue and blood are determined. The power of laser radiation (LR) was taken into account in boundary conditions set for the center of coagulated tissue volume. We also took into account the processes connected with changing of substance phase (vaporization). The original computer programs allow one to solve the problem varying in a wide range of the main parameters. Reasonable agreement was found between the calculation results and the experimental data for operations on macrosamples and on test animals.

Photothermal (PT) method is applied for a cell imaging and quantitative studies. The techniques for cell monitoring, imaging and cell viability test are developed. The method and experimental set up for optical and PT-image acquisition and analysis is described. Dual- pulsed laser set up combined with phase contrast illumination of a sample provides visualization of temperature field or absorption structure of a sample with spatial resolution 0.5 micrometers . The experimental optics, hardware and software are designed using the modular principle, so the whole set up can be adjusted for various experiments: PT-response monitoring or photothermal spectroscopy studies. Sensitivity of PT-method provides the imaging of the structural elements of live (non-stained) white blood cells. The results of experiments with normal and subnormal blood cells (red blood cells, lymphocytes, neutrophyles and lymphoblasts) are reported. Obtained PT-images are different from optical analogs and deliver additional information about cell structure. The quantitative analysis of images was used for cell population comparative diagnostic. The viability test for red blood cell differentiation is described. During the study of neutrophyles in norma and sarcoidosis disease the differences in PT-images of cells were found.

Our previous works concerned with the development of methods for studying blood and action of low-intensity laser radiation on blood and erythrocyte suspensions had shown the light- scattering methods gave a large body of information on a medium studied due to the methodological relationship between irradiation processes and techniques for investigations. Detail analysis of spectral diffuse reflectivities and transmissivities of optically thick blood layers, spectral absorptivities calculated on this basis over 600 - 900 nm, by using different approximations, for a pathological state owing to hypoxia testifies to the optical significance of not only hemoglobin derivatives but also products of hemoglobin decomposition. Laser action on blood is specific and related to an initial state of blood absorption due to different composition of chromoproteids. This work gives the interpretation of spectral observations. Analysis of spectral dependencies of the exinction coefficient e, mean cosine m of phase function, and parameter Q equals (epsilon) (1-(mu) )H/(lambda) (H - hematocrit) testifies to decreasing the relative index of refraction of erythrocytes and to morphological changes during laser action under pathology owing to hypoxia. The possibility to obtain physical and chemical information on the state of blood under laser action in vivo is shown to be based on the method proposed by us for calculating multilayered structures modeling human organs and on the technical implementation of this method.

The report deals with the investigation of the influence of N2-laser radiation on the kinetics of the initial specimens of the respiratory chain -- reactive oxygen forms (ROFs) -- depending on its parameters. It was shown, that the energy of N2-laser radiation promotes to the correction of the ROF generation and leads to an immunomodulation effect. We suppose that the immunomodulation effect is connected with a key molecule of the respiratory chain -NADP(H) and with the regulation role of ROF. We emphasize the necessity of correction of the pathological processes with hypo- and hyperfunction of granulocyte- macrophage cells by N2-laser radiation under the ROF generation kinetics control.

It is shown that reversible conformations (changes of spatial structure) of the cell components, responsible for the metabolic processes regulation, are the basis of biological activity and as a consequence therapeutic effect of low-intensity laser radiation. The physical mechanism of these changes is the reorientation of high regulated anisotropic parts-domains with the liquid- crystalline type of ordering due to the interaction between electric field of the laser lightwave and integral electric dipole of the domain (light induced analogue of Frederix's effect).

It is shown that infra-red ((lambda) equals 1064 nm) long pulse (approximately 100 microsecond(s) ) radiation of YAG:Nd laser, operating in free generation regime, effectively fragments gallstones, urinary calculus and kidney stones. The features of the mechanism of this process are investigated.

The laser action on chromosomes of living cells in the presence and absence of exogenous chromophore (ethydium bromide) was studied. Also investigated was the possible role of the endogenous chromophores, such as riboflavin, in this mutagenic action. We show that riboflavin induces DNA strand cleavages at N₂-laser irradiation. First the nonlinear mechanism of DNA cleavage by laser in the presence of riboflavin has been proven. Quantum yield of DNA strand cleavages by laser in the presence of riboflavin has been calculated.

It is shown that the efficacy of phototherapy of neonatal hyperbilirubinemia is considerably increased with substitution of traditional lamp sources by the argon laser light. The spectral range of the laser (476.5 - 514.5 nm) corresponds to low-frequency slope of bilirubin absorption spectrum. This rises quantum yield of lumirubin formation which is known for its high rate of excretion. The fact can be explained by the form of absorption spectrum of bilirubin which is the sum of two spectra of weakly bound chromophores, the spectrum of chromophore responsible for lumirubin production being shifted to lower frequencies. The second cause of higher efficacy of laser phototherapy with wavelength span 476.5 ... 514.5 is the less shielding effect of hemoglobin.

In the present paper the method and apparatus for percutaneous laser irradiation of blood (PLIB) in vessels (veins) are described. Results of clinical investigations of biostimulating effects under PLIB by red laser light (633 nm) in Cubiti and Saphena Magna veins are presented.

Dose dependences of the photolysis rate of erythrocytes and total fraction of leukocytes sensitized by hematoporphyrin have been investigated. It is shown that power index of the dose dependence is equal approximately to 2.2 and 1.4 for erythrocytes and leukocytes respectively, when cell photolysis occurred in a medium with neutral pH. This index for erythrocytes lysed in alkaline medium is equal approximately to 1.3. It is shown that the reason for such modification of the power index of photohemolysis dose dependence is not changing of photochemical processes but it consists in alteration of some light independent processes connected with pH-induced modification of membrane structure. It is suggested that such changing of membrane structure is related to the band 3 protein of erythrocyte membranes.

We present automated laser spectrofluorimeter and some applications of it. Laser spectrofluorimeter is fully automated. The lasers and all optical and electronic devices are controlled by the computer. The laser spectrofluorimeter can be used for measuring stationary fluorescence and anisotropy spectra, time-resolved fluorescence characteristics with temporal resolution from subnanoseconds to milliseconds: (1) instantaneous florescence spectra (0.1 ns - 10 ms); (2) fluorescence kinetics and lifetime of the excited state (0.05ense - e10ems, after mathematical treatment); and (3) anisotropy spectra and anisotropy kinetics (0.1 ns - 10 ms). Experimental data can be treated with a full set of programs: (1) deconvolution of fluorescence pulse with up to 3-exponent approximation; (2) calculation of anisotropy kinetics with simultaneous deconvolution for different polarization; (3) calculation of instantaneous spectra from fluorescence decays; and (4) mathematical treatment of spectra (position of spectrum, halfwidth, asymmetry, etc). Laser spectrofluorimeter was tested on a number of objects (dye solutions, fluorescent probe in phospholipid bilayer and red blood cell membranes, humus substances in natural water, etc.) and demonstrated its high versatility.

A new modification of distributed feedback dye laser (DFDL) which is well suited for spectroscopical applications in biology and in other fields is presented. Due to the original arrangement for the pumping of the dye solution the proposed novel DFDL provides the stable generation of picosecond pulses continuously tunable from near UV to near IR when TEA N₂-laser is used as the pump source.

In the last few years radiation sources on the basis of stimulated Raman scattering (SRS) have been sufficiently widely used in spectroscopy. Of great importance therein are high efficiency of radiation conversion to one, usually first Stokes (FSC) or anti-Stokes (FASC) component of SRS, small divergency of converted radiation flux, stability of reproduction of its energy and time characteristics. SRS is a process of amplification of quantum noises. Therefore, quantum noise is one of the sources of fluctuation of temporal, energy, and spectral parameters of converted light. The stability of SRS radiation pulses is strongly influenced by fluctuations of laser radiation parameters. The design features of Raman shifters and properties of scattering medium influence SRS efficiency and converted flux divergency. As a result, fluctuations of converted radiation parameters can reach dozens percent, radiation divergency can be about 10^-2 rad, and efficiency of SRS-conversion to one component doesn't usually exceed 10 divided by 20%. In our paper results on experimental study of SRS regimes and geometrical factors influence on statistical properties (fluctuations of energy and instantaneous intensity) of pulses of forward, backward FSC, FASC of SRS and depleted pump as well as on efficiency of SRS process are briefly presented. On the basis of the investigations made we discuss the ways of creating SRS-based radiation sources with high quantum efficiencies (>= 70%) of conversion into FSC, close to diffraction divergency (approximately equals 0.5 mrad) of converted flux and high stability (variation coefficient <EQ 6%) of energy parameters

Energy absorption, heat transfer, thermodenaturation and vapor blanket formation, under the action of laser radiation pulse on pigmented spherical granules in heterogeneous laminated biotissues are investigated theoretically.

Monitoring of photosynthetic organisms (PSO) -- phytoplankton and terrestrial vegetation -- is one of the most important tools for controlling the ecological state of the environment. Being the primary element of a trophic chain, PSO play a significant role in the functioning of an ecological system, because they provide an inflow of oxygen into water and the atmosphere and regulate the carbon-dioxide content. Sometimes it is principally necessary to use remote quick-response techniques. In this paper we consider spectroscopic methods that imply an analysis of the optical characteristics of the objects under study and are most convenient in remote regime. Remote methods can be divided into passive and active ones. Passive methods require comparatively simple equipment and, hence, are cheap. They can be used from an aircraft or a satellite providing thus an ability of monitoring large areas. However, results obtained from the Earth's surface albedo can be used only for rough estimations and, as a rule, require calibration on specially selected polygons. Active methods based on exciting and detecting a fluorescent response from the object, are free of these drawbacks. In many cases, the possibility of controlling the regimes of pumping and detection eliminates an ambiguity of the result of measurements and improve their informativity. However, for such methods, the

Results of lidar investigating atmospheric aerosol parameters at regions of large industrial centers have been presented. Technical characteristics and design of lidar stations are described. Optical parameter spectra of industrial aerosol are different from background ones. Investigating processes of aerosol pollution spread from large factories have been carried out.

The intracavity laser spectrometer with graphite furnace electro-thermal atomizer and high- resolution echelle spectrograph that provides determination of trace amounts of lithium, strontium, barium and manganese in water is described. The detection limits of elements tested are as a rule much lower than those obtained by modern conventional spectrometers. They are: 0.03 ng/l for lithium, 0.15 ng/l for strontium and 0.2 ng/l for barium. This laser method and equipment are also proposed for direct determination of trace iodine contents in water and biological media with minimal sample preparation in conditions of laser probing vapors over a surface of heated liquid in a closed cell. The detection limit of iodine molecules is 15 (mu) g/l. Linear standard calibration curves were considerably extended by measuring total absorption of elements in laser spectra. The precision of the intracavity analysis was found to be approximately 10% for the lowest element content.

The possibilities of laser fluorescence spectroscopy for diagnostics of different kinds of organic substances such as petroleum hydrocarbons, humic substances, and proteins in natural water are discussed. The algorithm to determine the contributions of these organic complexes in fluorescence spectra from natural water are suggested and results of natural water monitoring during an expedition in the Black Sea are discussed.

The present-day ecological situation calls for lidar systems based on CO₂ lasers. However, the spectral tuning range of a conventional CO₂ laser is limited by a discrete set of oscillation lines on the regular bands 00⁰1 - 10⁰0, 00⁰1 - 02⁰0. Therefore, the possibility of using such lasers for atmospheric monitoring is limited and depends on accidental coincidence of radiation frequencies and absorption resonances of chemical compounds polluting the atmosphere. Besides, the presence of carbon dioxide in the environment leads to significant losses due to the absorption at its transmission in the atmosphere for considerable distances. We and other investigators obtained powerful radiation pulses at a sufficiently high efficiency in a TEA CO₂ laser on nontraditional bands: the sequence (00⁰2 - 10⁰1, 00⁰2 - 02⁰1) and the hot (01¹1-11¹0) bands, which more than doubles the radiation spectrum of conventional CO₂ lasers thus widening their potentialities for atmospheric monitoring. It is also important that the radiation of nontraditional bands practically is not absorbed by atmospheric carbon dioxide. In this paper, we present a UV-preionization TEA CO₂ laser tunable over the lines of regular and nontraditional bands specially designed for atmospheric monitoring. Developing it, we took into account the fact that atmospheric monitoring places certain demands on lasers: high stability of output performances, a comparatively narrow oscillation line, low beam divergence, possibility of working in pulse-periodic regime. Besides, the laser has high energy performances and the widest possible spectral range of tuning. Special consideration was given to the real problem of tunable CO₂ lasers -- automatization of the process of tuning over oscillation lines. On the basis of this laser a lidar system was created which has passed an in- the-field test to satisfaction. With its use small concentrations (at a tolerable-concentration level) of a number of gaseous pollutants was determined.

In the paper, a cw CO₂ (CO) laser with automatic tuning over oscillation lines and stabilized output parameters is described. The transfer of oscillation from carbon dioxide to carbon monoxide only takes place when the series-produced sealed-off active element GL-501 is replaced by the constructively identical element GL-509. The laser oscillates in the 9.1 - 11.3 micrometers range (100 vibrational-rotational lines of the 00⁰1-10⁰0(02⁰0) band and more than 20 lines of the 01¹1-11¹0 band's P-branch of the CO₂ molecule when GL-501 is used) and in the 5.2 - 6.4 micrometers range (more than 100 vibrational-rotational lines of the CO molecule when GL-509 is used). The output power in the single-mode regime is more than 10 W at oscillation on CO₂ (on weak lines -- 1 W at least) and more than 1 W at oscillation on CO (on weak lines -- 0.05 W at least). The CO₂ (CO) laser with the above parameters operated satisfactorily for a long time as a component of a trace gas analyzer and it was used also for local control of gaseous atmospheric pollutants by the method of PA-detection. For the purpose of widening spectral possibilities of the CO₂ (CO) laser for working gas analyzer problems the oscillation of the CO₂ laser radiation second harmonic in the AgGaSe₂ crystal of a high optical quality has been obtained. The convertor efficiency factor about 0.15% with the laser output power approximately 5 W directed onto crystal has been realized.

The experimental set-up using a cw ¹³C¹⁶O₂-laser for the real time multicomponent PA gas analysis is described. An intracavity PA-cell combining the `H-' and `T-'geometries simultaneously is used. The applying of a computer for laser lines tuning and a Fourier transform technique for signal processing permits us to obtain the minimum detectable absorption of 1 X 10^-9 cm^-1 with a time resolution of 30 seconds per one line. The concentrations of gas mixture component are determined by solving the linear equation systems with using a least-squares technique. The results of the experiments on detecting H₂O, CO₂, NO₂, NH₃, HNO₃, OCS and C₂H₄ in urban air are reported.

The different spectral-luminescence characteristics of humic substances were investigated. Hypothesis for the origin and the structure of fluorescence band from humic matter are discussed.

A fluorescent study of aquatic humic substances (AHS) in ice has been performed in order to make the first step toward elaboration of a remote technique for their diagnostics in aqueous solid-phase-containing systems. The fluorescence spectra of AHS in ice samples were obtained for different temperatures ranged from 0 to 150 degree(s)C. An unusual distortion of the fluorescence band shape has been observed at low temperatures. Some conclusions on the form of presence of AHS in ice were made on the base of the spectroscopic study. Several specific experiments were carried out to characterize the crystallization process in AHS aqueous solutions.

Ellipticine has been taken as a model for antitumoral compounds having weak base properties (7 < pK < 8.5). The protonation state and intracellular distribution of the drug were investigated in single living cells by confocal laser microspectrofluorimetry. These processes appear to be mainly mediated by transmembrane electric potentials and subcellular local pHs, as well as by the modification of the protonation equilibrium of the drug when bound to various biological macromolecules.

The recent data on the influence of phytochrome on the efficiency of Ca²⁺ translocation across the membranes of oat protoplasts are given. Ca²⁺ uptake in the protoplasts was shown to be influenced by the red light (R) illumination. This effect was reverted by the following far-red light (FR) illumination. To elucidate the sensitivity to phytochrome-controlling action the screening between the mechanisms of Ca²⁺ transport across the plasma membranes of oat protoplasts, Na⁺/Ca²⁺ and Ca²⁺/H⁺ exchangers, Ca²⁺-pump and Ca²⁺-channel was done. It was established that phytochrome modulated the activity of Na⁺/Ca²⁺-exchanger and Ca²⁺-pump. The light-mediated oscillations of cytoplasmic Ca²⁺ concentration in the oat protoplasts were demonstrated using fluorescence probe quin2 loaded into the cells and laser monitoring of fluorescence signal. The evidences were obtained that the oscillations were not the result of the elevation of cytoplasmic Ca²⁺ concentration and had no connection with Ca²⁺ pool of mitochondria. The possibility of the relation between the Ca²⁺ oscillations and phosphoinositide metabolism in plant cell membranes is analyzed. The mechanisms of transformation of primary phytochrome signal into biological effects were discussed.

Highly phosphorescent photosensitizer Pd-tetra (o-methoxy-p-sulfo) phenyl porphyrin (Pd- MSPP) was used to follow the primary events of photodynamic action -- quenching of triplet states by free oxygen in different systems: water solutions of proteins, cells and tissues in vivo and in vitro. The photosensitizer forms complexes with proteins in solutions and biosystems showing remarkable hypsochromic shifts of band and an increase of the quantum yield and lifetime of phosphorescence at the binding to proteins. In absence of oxygen the lifetime of phosphorescence is almost single exponential, depends on the energy of the lowest triplet state of the sensitizer. The photochemical quenching of the triplets by cell components is negligible. In the presence of free oxygen the quenching of the sensitizer triplets takes place. The emission spectrum of singlet oxygen with maximum 1271 nm was recorded in water protein solutions and quantum yield of sensitized luminescence was measured. In the systems studied oxygen consumption was detected and oxygen concentration was estimated in the course of photodynamics by an increase in photosensitizer phosphorescence lifetime, using laser flash photolysis technique. At least two exponential kinetic of the phosphorescence decay shows that the distribution of the free oxygen is not uniform in tissues. The unexpected effect of photoinduced hyperoxia was observed just after the several minutes of tumor exposition with following slow development of a hyposia in a course of continual light exposition.

The fluorescence lifetimes of merocyanine 540 (MC 540) in ethanol, methanol, and suspensions of DMPC and DPPC liposomes were studied using a laser-based time-correlated single photon counting system. Time-resolved fluorescence of MC 540 in methanol and ethanol can be analyzed with a single-exponential model, fluorescence decays of MC 540 in lecithin suspensions show biexponential behavior. We also present basic information about time-resolved fluorescence analysis software, designed and used by the authors as an integrated data station.

The photophysics of indoles is far from being understood, which hampers the application of fluorescence methods in the studies of tryptophan fluorescence emission in proteins. For investigation of effects of dipolar relaxations and formations of specific excited-state complexes in polar environments we applied the combination of time-resolved technique (analysis of excited-state lifetime distributions by maximum entropy method) with site- selective excitation (red-edge) effects. They demonstrate, that in polar protic solvents the relaxational contributions to the distributions of lifetimes are characterized by unexpectedly narrow discrete components. They change their sign if the emission wavelength shifts from the short-wavelength to long-wavelength wing of the spectrum and disappear if the excitation is performed at the red edge (300 nm). They are characterized by significant temperature dependence with activation energy 25 - 30 kJ/mol (in isobutanol). In glycerol the situation is more complex: besides the dipole relaxational components, observed at sub-zero temperatures, other discrete short-living lifetime components are observed at room temperatures and above. They may be attributed to formation or rearrangement of the indole complexes with polar molecules after the dielectric equilibrium has been established.

The red (R) and far-red (FR) light irradiation were shown to induce Ca²⁺ concentration oscillations in cytoplasm of oat protoplasts. The inhibitors of Ca²⁺ pumps, sodium vanadate and 2,5-di-tert-butyl-1,4-benzohydroquinone (tuBHQ) influence these oscillations. The trigger of Ca²⁺ oscillations is Ca²⁺ release from endoplasmic reticulum and vacuole but not mitochondria. The manifestation of regular Ca²⁺ oscillations depends on the concentrations of oat protoplasts in suspension that suggests the propagation of a signal between the cells and synchronization of their light- induced Ca²⁺ oscillations response.

The luminescent analysis with nano- and millisecond time resolution of intramolecular dynamics of Escherichia coli alkaline phosphatase was carried out. The effect of pH within the range 7.2 - 9.0, thermal inactivation, limited proteolysis by trypsin, binding of pyrophosphate, interconversion of enzyme and apoenzyme, the replacement of Zn²⁺ and Mg²⁺ in the active site by Cd²⁺ and Ni²⁺ on the spectral and kinetic parameters of luminescence was investigated. The essential changes of the level of nano- and millisecond dynamics of protein structure were found to correlate with the shift of enzymatic activity. The importance of small- and large-scale flexibility of protein structure for the act of enzymatic catalysis realization was shown.

Conformational transformation of dissolved humic substances induced by NaOH and HCl addition in water has been investigated by automated subnanosecond laser spectrofluorimeter and fluorescence probe method. The equilibrium constants for binding of Rhodamine 6G to dissolved humic substances in water have been determined by a fluorescence quenching method. It is shown that the conformational structure of humic compounds in water depends on the intra- and intermolecular interactions. Spectral and viscosimetrical data in pH region 1.5 - 12.0 are interpreted in terms of conformational transformation of dissolved humic substances from a rigid globule to a flexible chain.

We present the results of the measurement of lateral diffusion rates of a sodium-potassium pump, reconstituted into large unilamelar liposomes. We present the results for enzymes, isolated from placenta of healthy mothers and mothers suffering from diabetes.

Using nanosecond laser excitation the (beta) -carotene S₁ emission has been detected in several solvents at room temperature and 77 K. The S₁ fluorescence spectrum was recorded in the near IR from 660 to 1250 nm. Time-resolved single photon counting with picosecond resolution confirmed the S₁ state origin of the fluorescence, and the detected fluorescence lifetime is close to the known S₁ state lifetime (about 10 ps at 293 K and 20 ps at 77 K). The S₁ emission vibrational structure in CS₂ can be interpreted with the S₁ level at 14300 cm^-1. The S₁ fluorescence quantum yield is about 25 times lower than that of the S₂ fluorescence. It is thus about 4 (DOT) 10^-6, from which the S₁ yields S₀ radiative lifetime can be calculated to be about 3 microsecond(s) .

A method of uniform representation of experimental data providing consideration of laser microirradiation influence on nerve cell impulse activity in physiological terms of excitation and inhibition is developed. The main types of cell response representations are studied. B- distribution function is offered for use as a parametric description of investigated processes.

First evidence of the excited state absorption in light-harvesting chlorophyll a/b complexes (LHCII) was obtained using nanosecond pump-probe beam technique in the frequency domain. LHCII preparations and photosystem II (PSII) membrane fragments showed absorption increase and decrease, depending on the pump beam intensity used. Non-linear absorption changes were observed in the narrow wavelength region around the pump wavelength of 620 and 647 nm (absorption bands of Chl b) but not at 670 nm (absorption of CHl a)². These data were interpreted in terms of excited state absorption of pigment-protein Chl a/b clusters within the subunits of LHCII especially by two-exciton excitations in the Chl-b region. We studied non-linear absorption properties of chromatophores of the purple bacterium Rhodospirillum rubrum at room temperature in the time domain using one-color pump-probe beam laser technique. Pump- and probe-beam wavelength was 590 nm. Two competing effects of non-linear absorption change could be detected -- an additional absorption and a bleaching. The relative strength of both effects was dependent on the pump intensity. Experimental results were interpreted in terms of excited state absorption in clusters of strongly interacting pigment molecules within the antenna system. Good agreement with the experimental results was achieved when they were compared with model calculations for the non-linear absorption in a three-level system of excitonic states from interacting BChl-a pigments.

Rebuilding the multipole structure of the three-level atoms in the resonant light field is investigated. The calculation of the quasi-energy spectra is based on the solution of the non- stationary Schrodinger equation. It is shown that in bichromatic pumping fields the three energy levels of the atom are split into the infinity number of quasi-levels. The investigation of the behavior of the biorganic structures and molecules in the weak and strong electromagnetic fields allows us to obtain the information about the fundamental processes and the mechanisms of the transference and the transformation of the excitement energy, the molecular organization and the structure of the reactive centers (RC). Approximately RC could be described by the model of the three-level system (TLS). In this work the TLS behavior in the bichromatic field is studied theoretically.

The wide use at present of laser radiation of low intensity in the clinics for treatment of different diseases and for the stimulation of the vital activity of organism is linked to a certain extent with the presence of corresponding laser apparatus. The special role here is attributed to the lasers that are capable of generating ultra-violet radiation of high spectrum brightness and energy effectivity. The arm of this research was creation and testing on biological objects of compact, autonomous excimer XeCl- and KrF-laser. Considering the simplicity and reliability of the laser devise, automatically preionized discharge-pumped laser of the LC-generator type can be the most advantageous candidate for practical use, since UV spark preionization automatically precedes the main discharge with the time delay determined by the excitation circuit parameters and other equipment can be eliminated. Due to using the excitation circuit of the LC-generator type the primary high voltage source of comparatively small value may be used.