SELF-ASSEMBLY OF AVIDIN AND STREPTAVIDIN WITH MULTIFUNCTIONAL BIOTIN MOLECULES

We report the synthesis of a water-soluble tetrafunctional biotin liga nd based on the porphyrin moiety and its behaviour at the air-water in terface. The addition of streptavidin or avidin to the subphase is sho wn to cause a significant expansion of the isotherm of the tetrabiotin ylated ligand, indicating a strong interaction between the protein and the ligand. The addition of inactive protein to the subphase caused n o such change from which it is deduced that non-specific interactions could not have been responsible for the effects observed with the acti ve proteins. Supplementary experiments using column chromatography pro vide evidence for the formation of a high molecular weight polymer whe n the tetrabiotinylated ligand and active protein are mixed.