Further studies of detergent-induced conformational transitions in proteins. Circular dichroism of ovalbumin, bacterial alpha-amylase, papain, and beta-lactoglobulin at various pH values. |
| |
Authors: | Y Y Su B Jirgensons |
| |
Affiliation: | Department of Biochemistry, The University of Texas System Cancer Center, M. D. Anderson Hospital and Tumor Institute, 6723 Bertner Avenue, Houston, Texas 77030 U.S.A. |
| |
Abstract: | The conformational transitions of ovalbumin, bacterial α-amylase, papain, and β-lactoglobulin were studied in the absence and presence of sodium dodecyl sulfate (SDS) between pH 2.75 and 12.0 by means of circular dichroism (CD) measurement. The weight ratios of SDS to protein in solutions were 14:1 in all experiments. The CD bands in the near-ultraviolet spectral region were strongly reduced by SDS, whereas those in the far-ultraviolet were enhanced. With the exception of the amylase, the mean residue ellipticities of the proteins at 222 nm were increased by SDS, especially in acidic solutions. At a pH of about 3.0, the [θ]222 values approached ?17 (±2) · 103 deg · cm2 · dmol?1. It is assumed that at a sufficiently low pH value the proteins which are complexed with SDS have a similar backbone conformation of moderate helical content. In alkaline solutions, the detergent effect was largely reduced due to electrostatic repulsion between the negatively charged protein and dodecyl ions. The near-ultraviolet spectra of ovalbumin, papain, and β-lactoglobulin at pH 6.4 were analyzed. Assignment of the resolved bands to the appropriate chromophores was also attempted. |
| |
Keywords: | To whom correspondence should be addressed. |
本文献已被 ScienceDirect 等数据库收录! |
|