3.4.2. FTIR

The infrared spectra of the samples were obtained with a Bruker FTIR spectrophotometer (Tensor27, Bruker, Madison, Germany) at room temperature. The samples were mixed with KBr by grinding at the ratio of 1:100 ( *w*/*w*). The wavelength range was 4000-400 cm<sup>−</sup><sup>1</sup> with a resolution of 4 cm<sup>−</sup>1. The signals were collected automatically over 32 scans and ratioed against a background spectrum recorded from KBr. The secondary structure of the samples was then analyzed with OMNICTM software (Version 8.2, Thermo Nicolet Corporation, Madison, WI, USA) and PeakFit software (Version 4.12, Systat Software Inc., San Jose, CA, USA).
