Photochemistry of triarylmethane dyes bound to proteins

Guilherme L. Indig

doi:10.1117/12.237542

2 April 1996 Photochemistry of triarylmethane dyes bound to proteins

Guilherme L. Indig

Proceedings Volume 2675, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy V; (1996) https://doi.org/10.1117/12.237542
Event: Photonics West '96, 1996, San Jose, CA, United States

Abstract

Triarylmethanes represent a class of cationic dyes whose potential as photosensitizers for use in photodynamic therapy of neoplastic diseases has never been comprehensively evaluated. Here, the laser-induced photodecomposition of three triarylmethane dyes, crystal violet, ethyl violet, and malachite green, non-covalently bound to bovine serum albumin (a model biological target) was investigated. Upon laser excitation at 532 nm, the bleaching of the corresponding dye-protein molecular complexes follows spectroscopic patterns that suggest the formation of reduced forms of the dyes as major reaction photoproducts. That implies that an electron or hydrogen atom transfer from the protein to the dye's moiety within the guest-host complex is the first step of the photobleaching process. Since the availability of dissolved molecular oxygen was not identified as a limiting factor for the phototransformations to occur, these dyes can be seen as potential phototherapeutic agents for use in hypoxic areas of tumors. These triarylmethane dyes strongly absorb at relatively long wavelengths (absorption maximum around 600 nm; (epsilon) _max approximately equals 10⁵ M^-1 cm^-1), and only minor changes in their absorption characteristics are observed upon binding to the protein. However the binding event leads to a remarkable increase in their fluorescence quantum yield and photoreactivity.

Citation Download Citation

Guilherme L. Indig "Photochemistry of triarylmethane dyes bound to proteins", Proc. SPIE 2675, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy V, (2 April 1996); https://doi.org/10.1117/12.237542

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