FTIR,THz and Raman spectroscopy of chymotrypsin: Effect of interaction with crown ether and denaturation

Abstract

Terahertz time-domain, FTIR and Raman spectroscopic techniques are used to study the interaction of chymotrypsin (CT) with 18-crown-6 (CE). The THz and FTIR spectra of CT demonstrate only three weak spectral lines whereas the spectra of the CT–CE mixtures exhibit several developed spectral features. Raman spectroscopy proves the presence of the bands in the low-frequency range. The results indicate that an increase in the functional activity of CT in nonaqueous solvents can be related to the interaction of the protonated amino groups of the protein with the CE molecules. FTIR and Raman spectra of lyophilized native and denatured protein are compared in the fingerprint and low-frequency ranges. Possible structural differences related to the spectral changes are discussed.