Distribution of protein Ramachandran psi (ψ) angle using non-resonance visible raman scattering measurements.

Knowing the distribution of Ramachandran angles helps in understanding peptide and protein backbone conformation. Empirical relations are proposed to correlate the spectral profile of the amide III3 band, obtained from ultraviolet resonance Raman measurements (UVRR), with the Ramachandran dihedral psi angle distribution in small peptide and protein molecules, in different environmental conditions (Mikhonin et al. J. Phys. Chem. B 2006, 110, 1928-1943). It has also been used for more complicated structures, like large globular proteins and protein fibrils. In our work here, we use visible Raman spectra and available empirical relations to obtain similar correlations for human serum albumin, hen egg white lysozyme, and human gamma crystallin. We also report the dihedral angle distribution in fibrils and a denatured protein in an ethanol environment using the same spectroscopic technique.