Effects of dimethyl sulfoxide, glycerol, and ethylene glycol on secondary structures of cytochrome c and lysozyme as observed by infrared spectroscopy
✍ Scribed by Ping Huang; Aichun Dong; Winslow S. Caughey
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 655 KB
- Volume
- 84
- Category
- Article
- ISSN
- 0022-3549
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✦ Synopsis
Effects of 1040% (vh) of dimethyl sulfoxide, glycerol, and ethylene glycol on the H-0-H bending vibration of water and the amide I bands of horse heart cytochrome c and chicken egg white lysozyme in 25 mM sodium phosphate buffer (pH 7.4) were examined at 20 "C by Fourier transform infrared spectroscopy. The H-0-H bending mode of water was strongly affected by these cryoprotectant solvents. Increasing the concentration of cryosolvents from 0 to 30% shifts the water bending band maximum from 1645 to about 1650 cm-l. Second-derivative analysis reveals significant changes in conformation-sensitive amide I regions of lysozyme ascribed to a-helix (1657 cm-l), turn (1674 cm-I), and unordered (1646 cm-l) structures; each cryosolvent increases the intensity of the 1657 cm-l band at the expense of bands at 1674 and 1646 cm-l. No changes in spectra deemed significant were observed for cytochrome c under the same conditions. There is no spectral evidence of structural randomization of proteins due to the presence of these cryosolvents. Cryosolvent-induced changes in secondary structure of proteins may result from changes in water structure which, in turn, perturb the structure of the protein and/or from direct interactions between cryosolvent and protein.