Solubility-composition Relations of Gluten Proteins

Abstract

IT is thought that the tertiary structure of a globular protein in aqueous solution is quite largely conditioned by the interactions between the amino-acid residues and water. In general, the expected result is a folding of the polypeptide chain(s) such that the charged residues are at the surface of the molecule while the uncharged residues are packed in the central regions of the molecule. The structure is stabilized by hydrophobic interactions and intra-chain hydrogen bonding in the interior, and at the surface by hydrogen bonding with water¹. The ability of this theory to account for the behaviour of some globular proteins has led to attempts to derive relationships between composition and structure that may have predictive value. Two examples are Fisher's “law”² and Hatch's³ polar ratio. In 1908, proteins were classified by British and American committees according to their solubility⁴; there may therefore be a relation between this classification and the predictions obtained by applying the suggestions of Fisher and Hatch. Grlutenin and gliadin, the exemplars of two of the nine solubility classes of simple proteins, were used in an attempt to predict their properties in solution from their amino-acid composition.