Structural analysis of some soluble elastins by means of FT-IR and 2D IR correlation spectroscopy

Abstract

Fourier transform infrared (FT-IR) spectroscopy combined with 2D correlation spectroscopy has been used to offer some information about stability and structure of some soluble elastins. Temperature has been chosen as the perturbation to monitor the infrared behavior of various soluble elastins, namely, α-elastin p, α-elastin, and k-elastin. In the 3800-2700 cm⁻¹ region, the H-containing groups were analyzed. The bonded hydroxyls are found to decrease prior to the NH-related hydrogen bonds and also to the conformational reorganization of hydrocarbon chains. The transition temperatures were evaluated and they were found to agree with those obtained from DSC data. The FTIR spectra and their 2nd derivatives denote that α- elastins exhibited amide-I, -II and -III bands at 1656, 1539 and 1236 cm⁻¹, respectively, while in k-elastin these bands were found at 1652 cm⁻¹ for amide I, 1540 cm⁻¹ for amide II and 1248 cm⁻¹ for amide III. The macroscopic IR finger-print method, which combines: general IR spectra, secondary derivative spectra, and 2D-IR correlation spectra, is useful to discriminate different elastins. Thus using the differences of the position and intensity of the bands from "fingerprint region" of studied elastins, which include the peaks assigned to C==O, C--C groups from α-helix, β-turn, and the peaks assigned to the amide groups, it is possible to identify and discriminate elastins from each others. Furthermore, the pattern of 2D-IR correlation spectra under thermal perturbation, allow their direct identification and discrimination.