A Circular Dichroism and Fluorescence Spectrometric Assessment of Effects of Selected Chemical Denaturants on Soybean (Glycine max L.) Storage Proteins Glycinin (11S) and β-Conglycinin (7S)

Abstract

Soybean glycinin (11S) and beta-conglycinin (7S) were subjected to select chemical treatments at various concentrations and resulting changes in protein structures were investigated by circular dichroism (CD) and fluorescence spectrometry. Fluorescence quenching results indicated that urea >/=3 M caused significant unfolding of 11S, but not that of 7S. GuHCl was more effective than urea in denaturation of 11S. A two-step transition in 11S structure was observed with a possible existence of a folding intermediate at 2.5 M GuHCl. Sodium dodecyl sulfate (SDS) measurably altered secondary and tertiary structures of 11S and 7S below SDS critical micellar concentration (CMC), possibly due to formation of mixed peptide-SDS micelles. SDS treatment increased alpha-helical and unordered structures of both proteins at the expense of beta-sheet structure. NaCl and CaCl 2 caused a significant decrease in fluorescence intensity without shifting emission lambda max. Exposure of 7S and 11S to NaSCN respectively at >/=0.3 and >/=0.6 M NaSCN caused a significant increase in fluorescence intensity measured at the corresponding lambda max of the protein. beta-Mercaptoethanol (beta-ME), N-ethylmaleimide (NEM), and phytic acid caused variable red shifts, 2.5-4 nm, in the emission lambda max.

Emulsifying properties and structural characteristics of β‐conglycinin and dextran conjugates synthesised in a pressurised liquid system

“…Untreated reaction mixtures show troughs in the CD curve at 216 nm, and no significant difference with purified β‐conglycinin (data not shown). Furthermore, the secondary structures of β‐conglycinin consisted of 10.7%α‐ helix, 36.9%β‐ sheet, 21.5%β‐ turn, and 29.4% disordered structure; this result is similar to other reports (Hou & Chang, 2004; Clare Sze et al. , 2007).…”

Physicochemical and Functional Properties of 2S, 7S, and 11S Enriched Hemp Seed Protein Fractions

“…The intrinsic fluorescence properties of a protein are determined by the location of its aromatic amino acid residues [ 24 ]. The 338–344 nm λmax obtained in this work is similar to the 344 and 340 nm reported for the 7S and 11S of soybean proteins [ 25 ]. The higher FI of the 11S protein at pH 3.0 indicates a more hydrophilic surface, which led to the packing of aromatic residues into the interior while the opposite was the case with the other protein fractions.…”

Nanoribbons Self‐Assembled from Triblock Peptide Polymers and Coordination Polymers

“…However, upon mixing 1 with ([Zn-L 2 EO 4 ] 2À ) n , the CD spectrum of the middle block exhibits positive ellipticity at 200 nm and negative minima at 210 nm and 220 nm (triangles). The spectrum can be attributed to a mixture of b sheets and a set of turns, [12,13] such that the turns occur at the histidine site of 1. Owing to the existence of turns in 1, the characteristic CD spectrum of 1 can never be completely the same as that of pure b sheets, which shows a deep minimum of larger than À5 kdeg dmol À1 cm 2 at about 215 nm.…”