Laser-excited Raman spectroscopy of biomolecules. I. Native lysozyme and its constituent amino acids

Laser-excited Raman spectra of a simple native protein, lysozyme, in aqueous solution are reported and partially interpreted with the help of the spectra of its constituent amino acids. Raman spectroscopy should be useful in providing direct evidence concerning the presence and number of disulfide cross-links in proteins, and may also be useful in studying the local conformation of the CSSC group. The aromatic side-groups of phenylalanine, tryptophan and tyrosine give rise to very intense and sharp lines. These lines are not sensitive to changes in conformation or state of aggregation. The peptide CONH group gives rise to two characteristic lines near 1660 (amide I) and 1260 cm^-1 (amide III). They appear to be potentially useful in assessment of conformational changes caused by denaturation. Lines in the region from 800 to 1150 cm^-1 arising from CC and CN stretching vibrations are also expected to be conformation-dependent.