title: Spectroscopic analysis of thermal denaturation of Cajanus cajan proteinase inhibitor at neutral and acidic pH by circular dichroism.
abstract: The conformational changes accompanying thermal denaturation under neutral, acidic and reducing conditions of Cajanus cajan proteinase inhibitor were investigated using near- and far-ultraviolet circular dichroism (CD) spectroscopy. The protein inhibitor shows a reversible N<-->D transition at neutral pH with a Tm approximately equal to 63 degrees C. The negative CD band intensities at 200 nm (far-UV) and near about 280 nm (near-UV) decrease as a result of thermal stress. The effect is more pronounced at low pH and in the presence of dithiothreitol. Only partial reversibility is observed under acidic conditions. Significant changes in the near- as well as far-ultraviolet CD spectrum are observed in the presence of dithiothreitol suggestive of the importance of disulfide linkages in maintaining the structure of C. cajan proteinase inhibitor.
authors.affiliation: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202 002, India.
authors.forename: Soghra Khatun
authors.initials: SK
authors.lastname: Haq
authors.forename: Rizwan Hasan
authors.initials: RH
authors.lastname: Khan
mesh_terms: D036561:Cajanus / Q000378:metabolism*; D002942:Circular Dichroism / Q000379:methods*; D004220:Disulfides / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances / Q000737:chemistry*; D008968:Molecular Conformation; D011480:Protease Inhibitors / Q000494:pharmacology*; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013696:Temperature; D013816:Thermodynamics; D014466:Ultraviolet Rays
chemical_list: D004220:Disulfides; D046911:Macromolecular Substances; D011480:Protease Inhibitors