Monitoring the secondary structure of proteins by near-infrared spectroscopy

Despite the numerous applications of near-infrared spectroscopy in the agri cultural and bio-industrial sectors, the relevance of this technique to the study of the secondary structure of proteins has received little attention . The present research investigated the near-infrared spectra of 12 model p roteins in the solid state by taking the corresponding mid-infrared data in to account. The second-derivative spectra of myoglobin, beta-lactoglobulin, and beta-casein in the near-infrared region revealed characteristic absorp tion bands. While myoglobin presented absorption bands at 2055, 2170, 2289, and 2350 nm, beta-lactoglobulin exhibited specific peaks at 2203, 2267, an d 2300 nm. The second-derivative spectrum of beta-casein showed a particula rly intense hand at 2269 nm. The results derived from a generalized canonic al correlation analysis confirmed the potential of near-infrared spectrosco py to characterize the secondary structure of proteins: 2172 and 2289 nm ap peared to be representative of alpha-helix structure; 2205, 2264, and 2313 nm were observed for beta-sheet; 2265 nm characterized the unordered struct ure.