Conformational changes induced by the interaction of sodium dodecyl sulfate with bovine plasma albumin

On the heterogeneity of serum albumin: effect of sodium dodecyl sulphate on agarose chromatography of the protein

The chromatographic behaviour of serum albumin changes if it is dissolved in an aqueous solution of sodium dodecyl sulphate (SDS) and is left at room temperature or is heated. Instead of emerging as one peak from an agarose column it emerges as more than one peak and the protein in each when rechromatographed elutes in more than one peak. Electropherograms made in the presence of SDS of the protein in these peaks show multiple banding from proteins migrating with a wide range of molecular weights. The chromatographic and electrophoretic behaviour of serum albumin in the presence of SDS suggests that the protein is not a simple monomer and alternative explanations for this behaviour are discussed.

Circular dichroic and fluoropolarimetric studies on tryptophyl residues in acid-induced isomerization of bovine plasma albumin

The acid-induced isomerization (the N-F transition) and expansion of bovine plasma albumin were studied by measuring circular dichroic spectra and fluorescence polarization of tryptophyl residues. Decreases in the magnitude of ellipticities at 208, 222, 262 and 268 nm were observed in the N-F transition and acid-expansion. However, increases in the magnitude of ellipticities at 295-300 nm observed in the initial part of the N-F transition exactly correlated with the increase of rotational relaxation time of tryptophyl side chains obtained by fluorescence polarization measurement.

Effect of dodecyl sulfate on the spectral properties of phenylalanyl residues in serum albumin detected by second derivative spectrophotometry

The effect of sodium dodecyl sulfate (SDS) on the spectral properties of phenylalanine residues in bovine serum albumin was studied at neutral pH by second derivative spectrophotometry. It was found that phenylalanine residues in the interior of bovine serum albumin became almost completely exposed on the surface of the protein on formation of a so-called AD12 complex. This conformational change began to be significant when 4 mol SDS bound to bovine serum albumin. At higher concentrations of SDS, when so-called ADn and AD2n complexes were formed, phenylalanine residues were transferred to the hydrophobic region again. This might be due to the involvement of phenylalanine residues in micelle-like clusters. Change in the conformation of bovine serum albumin involving tryptophan residues was also measured. These studies demonstrate the value of second derivative spectrophotometry in studies on conformational change of proteins.

Interaction of alpha-elastin with ionic detergents

Coacervation is known to be a fundamental step in elastogenesis that is influenced by various naturally occurring substances in connective tissue. Therefore, interaction of alpha-elastin with ionic detergents (sodium dodecyl sulfate, dodecylbenzyldimethylammonium bromide, cetyltrimethylammonium bromide, pentadecacarbethoxytrimethylammonium bromide and cetylpyridinium bromide) was studied as a model for the elastin interaction with amphipilic substances. The course of the interactions was followed by the effect on thermal coacervation, solubilization of lipophilic dye, difference spectra measurements and fluorescence probe. The results indicate that the detergents examined interact with alpha-elastin below critical micelle concentration in two different ways. In the first case, a mixed micelle can be formed from the detergent molecules (SDS, DBD) and alpha-elastin: alternatively mixed micelles are not formed, but the detergent molecules (CT, PCT, CP) do interact with elastin. The interaction of alpha-elastin at the isoelectric point was found to depend more on the chemical structure of the detergent molecule than on its charge. If detergent concentrations above the critical micelle concentration were applied, the interaction mechanism was different from that observed at lower detergent concentration.