Ultrafast geminate recombination and vibrational relaxation processes in ferrous nicotinate myoglobin

Marco A. Pereira; Alberto Boffi; Andrew Ridsdale

doi:10.1117/12.306114

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24 April 1998 Ultrafast geminate recombination and vibrational relaxation processes in ferrous nicotinate myoglobin

Marco A. Pereira, Alberto Boffi, Andrew Ridsdale

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Proceedings Volume 3273, Laser Techniques for Condensed-Phase and Biological Systems; (1998) https://doi.org/10.1117/12.306114
Event: Optoelectronics and High-Power Lasers and Applications, 1998, San Jose, CA, United States

Abstract

The photolysis, geminate recombination and vibrational relaxation of the low affinity ferrous myoglobin nicotinate complex have been studied by femtosecond transient absorption spectroscopy. This is an interesting system due to the peculiar interaction between ligand and protein fluctuations. This ligand is bulky and affects the naturally occurring protein fluctuations in a way similar to a doorstop precluding a door from closing totally. The whole Q band absorption transient spectrum of the photoproduct has been monitored starting from 100 fs to 100 ps. The time evolution of the spectrum has clearly shown two distinct phases, a vibrational cooling process occurring within 4 ps after the photolyzing pulse and a geminate rebinding process with a time constant of 28.8 +/- 0.1 ps. The transient spectra show different cooling rates for the different excited normal modes. The geminate rebinding process appears to be complete within 100 ps and hence appears to be the fastest geminate recombination process reported to date for a hemoprotein. This is the first report on the photolysis of a ferrous heme adduct with a nitrogenous base, previously considered as photoinert.

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Marco A. Pereira, Alberto Boffi, and Andrew Ridsdale "Ultrafast geminate recombination and vibrational relaxation processes in ferrous nicotinate myoglobin", Proc. SPIE 3273, Laser Techniques for Condensed-Phase and Biological Systems, (24 April 1998); https://doi.org/10.1117/12.306114

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