Spectroscopic characterization of gelonin--assignments secondary structure and thermal denaturation

Gelonin, a type 1 ribosome inactivating protein (RIP), having only one polypeptide chain, and which could be used against deadly diseases like cancer and AIDS is investigated spectroscopically through infrared (IR), diffused reflectance infrared fourier transform (DRIFT) and Raman techniques and observed vibrational modes are assigned. It is found that gelonin is having mainly alpha-helix and beta-sheet structure with some turn and disordered structure, the estimated percentage structure using Raman data being approximately 32% alpha-helix, approximately 20% beta-sheet, approximately 26% turn and approximately 22% disorder type. The temperature dependent infrared study of gelonin reveals its thermal stability, the denaturation temperature being around 60 degrees C and disordered contribution increasing with heating.