Raman spectroscopic study of the avidin—biotin complex

Abstract

Abstract Raman spectra of avidin, biotin and the avidin‐biotin complex were recorded. The percentages of secondary structure of avidin and the avidin‐biotin complex were obtained from the Raman spectra. The vibrational results indicate that, as a consequence of the interaction of avidin with biotin, the β‐sheet conformation percentage decreases and the α‐helical conformation percentage increases. Moreover, the interaction of avidin with biotin is also able to change slightly the tertiary structure of the protein. In fact, as a consequence of the binding of biotin, the hydrophobicity of the environment of Trp increases slightly according to the intensity increase of the 1360 cm −1 component. The intesity of all bands attributable to Trp residues increases with biotin binding, indicating that Trp is directly involved in the interaction. These results are in agreement with the results of UV measurements which indicate a red shift of the avidin Trp absorption bands as a consequence of the binding to biotin.