Conformation Analysis of Soybean Protein in Reverse Micelles by Circular Dichroism Spectroscopy

Abstract

Far-UV circular dichroism (CD) spectroscopy was used to study the conformation of protein from soybean flour under the influence of various reverse micelle environments and salt treatments, as compared with the protein using aqueous buffer extraction. These proteins exhibited characteristic CD spectra that reflected a considerable amount of residual secondary structures. The CD analysis showed that the protein modification by reverse micellar system was related to loss of α-helix and β-structure and increase of random coil. The ellipticity of protein in bis (2-ethylhexyl) sodium sulfosuccinate (AOT) and sodium dodecyl sulfate (SDS) reverse micelles was higher than in hexadecyl trimethyl ammonium bromide (CTAB) and TrionX-100. The CD spectra in reverse micelles except for SDS at 210 nm had lower intensity than in aqueous solution. Salts could influence the ellipticity of protein at near 194 nm in an order of NaCl > KNO3> > KCl > NaNO3 > Na2SO4 in monovalent salts and in MgCl2 > BaCl2 > CaCl2 divalent ones. Besides, the ellipticity was totally higher in monovalent salts than in divalent ones.