title: Raman and infrared spectra of toxin gamma from the venom of the scorpion Tityus serrulatus.
abstract: Toxin gamma is a basic, low-molecular-weight, neurotoxic protein, isolated from the venom of the Brazilian scorpion, Tityus serrulatus. Raman spectra (400-1800 cm-1 region) of this toxin in both the lyophilized state and in 0.1 M acetate buffer (pH 4.5) and the infrared spectrum (700-4000 cm-1 region) of a solid film were investigated. From the vibrational spectra, it can be concluded that the polypeptide backbone of toxin gamma consists of a mixture of the different secondary structures, with predominance of beta-sheet, followed by unordered structure and alpha-helix, with some evidence of beta-turn structures. The four disulfide bridges assume the gauche-gauche-gauche conformation of the CCSSCC fragments. The intensity ratio of the doublet at 853 and 828 cm-1 suggests that four out of the five tyrosine residues are exposed. The three tryptophan residues are exposed on the surface, and the single methionine residue assume the gauche-gauche conformation. Toxin gamma retains full activity in the pH 4.5-7.5 range, but is almost completely inactivated at pH 11.5.
mesh_terms: D000818:Animals; D004220:Disulfides; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D008715:Methionine; D051379:Mice; D010649:Phenylalanine; D011487:Protein Conformation; D012604:Scorpion Venoms / Q000633:toxicity; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D014364:Tryptophan; D014443:Tyrosine
chemical_list: D004220:Disulfides; D012604:Scorpion Venoms; D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan; D008715:Methionine