| Abstract
| - A highly hydrophilic peptide α-1 originated from the α-chain ofglobin was isolated by hydrophobicchromatography. The sizes and tertiary structures of peptide α-1monomer and aggregate wereexamined by the small-angle X-ray scattering (SAXS) method. Theradius of gyration (Rg) of peptideα-1 in 6 M urea exhibited no concentration dependence, suggestingthat peptide α-1 exists inmonomeric state in this solvent. In the absence of urea thescattering patterns are composed oftwo components, that is, high molecular weight and low molecular weightspecies. The Rg of thelow molecular weight component is consistent with the peptide α-1treated with 6 M urea, indicatingthat this low molecular weight constituent is the monomer of peptideα-1. The Rg of the highmolecular weight component increased with the peptide α-1concentration. The weight-averagemolecular weight of the aggregate oligomer obtained by SAXS method was7−9 times as large asmonomer peptide α-1, which was consistent with the result by thelaser light scattering study.Comparing the scattering pattern in the presence of 6 M urea withvarious theoretical models, themonomeric peptide α-1 took a random-coil structure and the polymerchain was distributedsymmetrically. The aggregates (oligomer) of peptide α-1 alsobehaved as a whole in random-coilstate and were formed by entanglement with the random-coilmonomer. Keywords: Globin; globin hydrolysates; peptide α-1; small-angle solutionX-ray scattering
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