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Cereal Chem. 71:155-159   |  VIEW ARTICLE

Intrinsic Fluorescence and Quenching Studies of Gluten Proteins.

S. G. Stevenson and K. R. Preston. Copyright 1994 by the American Association of Cereal Chemists, Inc. 

Intrinsic fluorescence and quenching studies of gluten protein extracts and their gel-filtration fractions were used to examine the location and environment of tryptophan residues in wheat gluten. The gluten protein was extracted with either 2M sodium thiocyanate (NaSCN), 0.05M acetic acid (HAC), 3M guanidine hydrochloride (GuHCl), or 3M urea. Samples for gel filtration were extracted with 2M NaSCN. Stern- Volmer quenching constants (KSV approximately 8) and accessibilities (74-124%) obtained for acrylamide quenching of gluten protein extracts indicated that the majority of the tryptophan residues are located on the surface of these proteins or in easily accessible (polar) regions. Emission maxima near 350 nm (EX = 295 nm) and a lack of change in the magnitude of Stokes' shift under denaturing conditions (8M GuHCl or 6M urea) supported this conclusion. Tryptophan residues from both high (glutenin) and lower (gliadin) molecular weight gel-filtration fractions showed similar results. Accessibilities to acrylamide ranged from 101-114%. Acrylamide and iodide Stern-Volmer quenching constants for the high molecular weight fraction (KSVacryl = 5.9, KSVI- = 1.1) showed values that were lower than those obtained for the low molecular weight fractions (KSVacryl = 10.1, KSVI- = 2.1), suggesting differences in the topography of these proteins in the regions in which these residues are located.

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