Near-infrared analysis of protein secondary structure in aqueous solutions and freeze-dried solids

✍ Scribed by Ken-ichi Izutsu; Yasuto Fujimaki; Akiko Kuwabara; Yukio Hiyama; Chikako Yomota; Nobuo Aoyagi

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 175 KB
• Volume: 95
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.20580

✦ Synopsis

Near-infrared spectroscopy (NIR) of various proteins (bovine serum albumin, lysozyme, ovalbumin, g-globulin, b-lactoglobulin, myoglobin, cytochrome-c) was investigated as a possible analytical method of the protein secondary structure in various physical states. The spectra of proteins in aqueous solutions (transmission mode, solvent-compensated) and those in freeze-dried solids (nondestructive diffuse reflection mode) showed several bands at similar frequencies in the combination (4000-5000 cm À1 ) and first overtone (5600-6600 cm À1 ) spectral regions. The normalized second-derivative near-infrared spectra of proteins in aqueous solutions suggested that some bands indicated a-helix (4090, 4365-4370, 4615, and 5755 cm À1 ) and b-sheet (4060, 4405, 4525-4540, 4865, and 5915-5925 cm À1 ) structures. The proteins mostly maintained spectra characteristic of their native structure after freeze-drying, although some reductions in a-helical structure and increase in unordered or b-sheet structures were observed. The near-infrared analysis also showed b-sheet formation of heat-treated BSA in aqueous solutions and in subsequently freeze-dried solids. The present results thus indicated that the nondestructive near-infrared analysis can be used for the investigation of dehydration-induced changes in protein secondary structures.