Antigen–antibody recognition by Fourier transform IR spectroscopy/attenuated total reflection studies: Biotin–avidin complex as an example

Biotin-avidin recognition is studied by Fourier transform ir spectroscopy/attenuated total reflection (FTIR/ATR) under physiological conditions. The ureido portion of biotin is confirmed to be involved in the interaction with avidin, as previously found, but when the biotin-avidin complex forms, an electrostatic interaction occurs between the carboxylate group of the biotin molecule and the protonated aminic end group of the avidin amino acid side chains. Comparison of the biotin-avidin system with the biotin-1,4-diaminobutane and biotin-tryptophan systems confirms these findings.