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Raman mode‐selective spectroscopic imaging of coenzyme and enzyme redox states
Author(s) -
Gu Min,
Lu H. Peter
Publication year - 2016
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.4915
Subject(s) - redox , chemistry , raman spectroscopy , flavin group , raman scattering , photochemistry , cofactor , nitric oxide synthase , electrochemistry , flavin adenine dinucleotide , enzyme , crystallography , inorganic chemistry , electrode , biochemistry , physics , optics
We investigate the surface‐enhanced Raman scattering (SERS) spectra of flavin monoucleotide (FMN) in its different redox states and in a redox active enzyme, nitric oxide synthase. Incubated with silver nanoparticles coated with silica, spectra for oxidized and reduced FMN are obtained at different electrochemical potentials. Dominate Raman mode shifts at 1623/1610, 1567/1550, and 1502/1492 cm −1 , belonging to typical redox‐sensitive region of FMN, are observed and analyzed, and they show a consistence with the results of spectral calculation by using the density function theory (DFT) method. We assign mode at 1500 cm −1 , composed of N 5 ―H bending, N 1 C 10a stretching and the asymmetric C 4a ―N 5 ―C 5a stretching, as a spectroscopic indicator for the redox states of FMN, because it shows a significant downshift (1502/1492 cm −1 ) and non‐linearly correction with potentials when FMN gets reduced from its full oxidized state electrochemically. Isolated FMN domain from a wild type neuronal nitric oxide synthase enzyme (nNOS) is also studied with the same experimental approach. We have observed similar Raman mode down‐shifting as that of the pure FMN, which further supports our conclusion that the mode at ~1500 cm −1 indicates redox states for FMN, the coenzyme of nNOS, even in redox protein matrix. Copyright © 2016 John Wiley & Sons, Ltd.