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Abstract:
Vibrational spectra of red fluorescent protein DsRed have been studied for the first time by polarization-sensitive multiplex coherent anti-Stokes Raman scattering at two excitation wavelengths, 545 nm and 583 nm, in resonance with the absorption bands of the immature "green" and mature "red" protein chromophores. Overall vibrational patterns of both DsRed chromophores were found to be similar to each other and to differ substantially from that of S65T-GFP at pH8. Our data suggest that both "green" and "red" DsRed forms possess an extended chromophore structure, and, consequently, that maturation of red fluorescence is governed bz the interactions with the protein environment after isomerization around a cis peptide bond between Phe 65 and Gin 66. Besides, a coexistence of the major anoinic and minor neutral DsRed species can be suggested from virbational features in 1600-1700 cm-1 range; the hypothesis awaits verification after the detailed assignment of vibrational modes for the DsRed chromophore.
