Study of the interaction between phosphorylase and hydrophobic groups by means of affinity electrophoresis

A homologous series of water-soluble alkyl-dextrans varying in the length of their hydrocarbon side-chain [-NH-(CH2)n-CH3; n = 1-5] were synthesized. When alkyl-dextrans were entrapped in polyacrylamide gel, the electrophoretic mobility of phosphorylase was retarded by hydrophobic interaction between phosphorylase and the immobilized alkyl groups. The dissociation constants of rabbit brain phosphorylase, rabbit skeletal muscle phosphorylase a and b and potato glycogen and starch phosphorylases were calculated from the extent of the retardation of mobility as a function of the concentration of the alkyl groups. As the length of the hydrocarbon side-chains of alkyl groups increased, the affinity of the phosphorylases for the alkyl groups increased. The introduction of a hydroxyl or an amino group at the terminal position of the hydrocarbon side-chain diminished the affinity.