The Raman spectra of lysozyme, ribonuclease, and BSA (bovine serum albumin) in aqueous solution extracted by nitrobenzene and the ultra-violet visible absorption spectra of BSA in aqueous solution have been studied. It has been proven that the structure of all the characteristic Raman and UV bands of BAS protein in aqueous solution is due to α-helical and random-coil conformations. The tyrosine residue is "exposed", and the conformation of the carbon atoms in the disulfide bridge c-c-s-s-c-c is trans-gauche-gauche. The influence of adding nitrobenzene to lysozyme, ribonuclease, and BSA aqueous solution has been studied. The study indicated that nitrobenzene treatment of protein aqueous solution is an efficient means for obtaining better Raman spectra.
Ke Weizhong and Wu Jianzhong, "Influence of the Nitrobenzene Extraction Technique on the Protein Molecule Conformation," Appl. Spectrosc. 48, 209-213 (1994)