Interactions and compatibility of ribuloso-1,5-bisphosphate carboxylase/oxygenase from alfalfa with pectin in aqueous medium

HPLC, dynamic light scattering, CD- and fluorescent spectroscopy, and phase analysis methods are used to study the effect of Coulomb and non-Coulomb interactions between alfalfa rubisco and pectin on their thermodynamic compatibility. In the acid region of pH, water insoluble interpolymer complexes stabilized by both the Coulomb and non-Coulomb bonds are formed. In the neutral and alkaline regions, the complexes soluble in water are formed via non-Coulomb bonds, due to both the hydrophobic interaction involving the ester groups of pectin and the hydrogen bonding between dissimilar molecules. The compatibility of these biopolymers is sensitive to the esterification degree of pectin. With the latter increasing, compatability increases at neutral pH, but decreases considerably in the acidic region. (C) 2000 Elsevier Science B.V. All rights reserved.