Near-infrared analysis of protein secondary structure in aqueous solutions and freeze-dried solids.
Near-infrared spectroscopy (NIR) of various proteins (bovine serum albumin, lysozyme, ovalbumin, gamma-globulin, beta-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(-1)) and first overtone (5600-6600 cm(-1)) spectral regions. The normalized second-derivative near-infrared spectra of proteins in aqueous solutions suggested that some bands indicated alpha-helix (4090, 4365-4370, 4615, and 5755 cm(-1)) and beta-sheet (4060, 4405, 4525-4540, 4865, and 5915-5925 cm(-1)) structures. The proteins mostly maintained spectra characteristic of their native structure after freeze-drying, although some reductions in alpha-helical structure and increase in unordered or beta-sheet structures were observed. The near-infrared analysis also showed beta-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.
Izutsu
Ken-Ichi
K
National Institute of Health Sciences, Kamiyoga, Setagaya 158-8501, Tokyo, Japan. Izutsu@nihs.go.jp
Fujimaki
Yasuto
Y
Kuwabara
Akiko
A
Hiyama
Yukio
Y
Yomota
Chikako
C
Aoyagi
Nobuo
N
D005612:Freeze Drying; D007782:Lactoglobulins / Q000737:chemistry; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D012996:Solutions; D019265:Spectroscopy, Near-Infrared; D014867:Water / Q000737:chemistry; D005719:gamma-Globulins / Q000737:chemistry
D007782:Lactoglobulins; D011506:Proteins; D012996:Solutions; D005719:gamma-Globulins; D014867:Water; D012710:Serum Albumin, Bovine