Conformational modifications of alpha gliadin and globulin proteins upon complex coacervates formation with gum Arabic as studied by Raman microspectroscopy.
As a molecular model of gelatin-free coacervates, complexes of pea globulin and alpha gliadin proteins with gum arabic prepared at different acidic pH values are studied using Raman microspectrometry. Raman spectra confirm higher content of beta-sheets and random coils in pea globulin and dominating alpha-helical structures in alpha gliadin. For protein-gum arabic complexes, Raman data support the existence of specific pH conditions for optimal complex coacervation (pH 2.75 for globulin and pH 3.0 for gliadin(1)), when (i) pH-induced conformational perturbations of free protein structure are the strongest and (ii) compensation of these perturbations by gum arabic is the most pronounced. Conformations implied in the protein-gum complexes are mainly beta-sheets in pea globulin and alpha-helix in alpha gliadin. The role of electrostatic and non-Coulombic interactions (intermolecular hydrogen bonds) in stabilizing of protein-polysaccharide complexes is discussed in relation with the overall structure and the charge density profile of these two proteins.
Chourpa
Igor
I
Laboratoire de Chimie Analytique, UFR de Pharmacie, IFR 135 Imagerie Fonctionnelle, Université François Rabelais de Tours, 31, avenue Monge, 37200 Tours, France. chourpa@univ-tours.fr
Ducel
Virginie
V
Richard
Joël
J
Dubois
Pierre
P
Boury
Frank
F
D001672:Biocompatible Materials / Q000737:chemistry*; D001709:Biotechnology / Q000379:methods; D005903:Gliadin / Q000737:chemistry*; D005916:Globulins / Q000737:chemistry*; D006170:Gum Arabic / Q000378:metabolism*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D008968:Molecular Conformation; D011134:Polysaccharides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods*; D055672:Static Electricity
D001672:Biocompatible Materials; D005916:Globulins; D046911:Macromolecular Substances; D011134:Polysaccharides; D011506:Proteins; D006170:Gum Arabic; D005903:Gliadin