Ultraviolet resonance Raman study of the avidin biotin complex

An ultraviolet resonance Raman, UVRR, spectroscopic study of avidin and avidin/biotin, at ph 7.5, performed with 244 mn excitation, resolves spectral contributions from the tyrosine 33 and tryptophan residues. The UVRR difference spectrum of hole avidin minus apo avidin, reveals details of the changes to avidin's tyrosine 33, No change in the hydrogen bonding state of tyrosine 33 is detected, but a change to a more hydrophobic environment is indicated upon addition of biotin, Tryptophan bands dominate the difference spectrum, with changes corresponding to the movement of tryptophan tortional angles being observed. The increase in tryptophan UVRR bands upon addition of biotin indicates a change to a more hydrophobic environment, highlighting the importance of hydrophobic interactions in the observed strong avidin/biotin binding. Copyright (C) 2000 John Wiley & Sons, Ltd.