Temperature scanning FTIR analysis of secondary structures of proteins embedded in amorphous sugar matrix.
Heat-induced changes in secondary structures of five proteins (bovine serum albumin, BSA; human serum albumin, HSA; myoglobin; ribonuclease A, RNase A; and, beta-lactoglobulin, beta-Lg) in an amorphous sugar matrix were analyzed by temperature-scanning Fourier transform infrared spectroscopy to elucidate the mechanism of heat-induced conformational change of solid-phase proteins. Three sugars, trehalose, maltose, and dextran (MW 6000), were used. Loss of alpha-helices due to increasing temperature was observed for BSA, HSA, and myoglobin, which are rich in alpha-helices. RNase A showed a marked decrease in predominant secondary structural components (beta-sheet) with increasing temperature. However, no noticeable changes in the content of secondary structures, except for a slight loss of alpha-helices, were observed for beta-Lg, which is also beta-sheet-rich. These heat-induced conformational changes were significant at temperatures above the glass transition temperature. The heat-induced conformational change in BSA dried with sugar appeared time-independent and was clearly different from that due to dehydration and from the thermal conformational change for a solution of BSA. In particular, differences in secondary structural components that increased due to loss of alpha-helices were noted.
Imamura
Koreyoshi
K
Faculty of Engineering, Department of Bioscience and Biotechnology, Okayama University, Okayama 700-8530, Japan. kore@cc.okayama-u.ac.jp
Ohyama
Ken-Ichi
K
Yokoyama
Toru
T
Maruyama
Yoshinobu
Y
Kazuhiro
Nakanishi
N
D000818:Animals; D002417:Cattle; D003911:Dextrans / Q000737:chemistry; D005936:Glucans / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D008320:Maltose / Q000737:chemistry; D044367:Phase Transition; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D011506:Proteins / Q000032:analysis* / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014199:Trehalose / Q000737:chemistry
D003911:Dextrans; D005936:Glucans; D011506:Proteins; D008320:Maltose; D014199:Trehalose