Raman spectroscopic studies of complexes of biotin and biotin derivatives with avidin

Avidin (Avi) is a basic tetrameric glycoprotein (128 × 4 amino acid residues, Mr = 62, 400) isolated from egg white. The protein binds up to four molecules of biotin (Bio) with exceptionally high affinity (pKd = 15.3) [1], suggesting a possible function of Avi as an antibiotic protein inhibiting bacterial growth. The unusually high affinity of Avi for Bio, and its derivatives has been exploited widely for the development of molecular tools in affinity chromatography, affinity cytochemistry, immunoassays, diagnostics and as biosensors [2].