The behavior of threonine residues in the bacteriorhodopsin (bR) photocycle has been investigated by Fourier transform infrared difference spectroscopy. L-Threonine labeled at the hydroxyl group with 18O (L-[3-(18)O]threonine) was incorporated into bR and the bR-->M FTIR difference spectra measured. Bands are assigned to threonine vibrational modes on the basis of 18O induced isotope frequency shifts and normal mode calculations. In the 3500 cm-1 region, a negative band is assigned to the OH stretch of threonine. In the 1125 cm-1 region, a negative band is assigned to a mixed CH3 rock/CO stretch mode. The frequency of both these bands indicates the presence of at least one hydrogen bonded threonine hydroxyl group in light adapted bR which undergoes a change in structure by formation of the M intermediate. Spectral changes induced by the substitution Thr-89-->Asn but not Thr-46-->Asn or Asp-96-->Asn are consistent with the assignment of these bands to Thr-89. These results along with another related study on the mutant Thr-89-->Asn indicate that the active site of bR includes Thr-89 and that its interaction with the retinylidene Schiff base and Asp-85 may play an important role in regulating the color of bacteriorhodopsin and the transfer of a proton to the Schiff base.

요약. 고에너지 화합물의 수소결합 현상을 연구하기 위하여 nitromethane 단량체(monomer)와 이합체(dimer)에 대하여 Gaussian-98 프로그램을 사용하여 restricted BLYP/6-311++G(d,p), B3LYP/6-311++G(d,p), MP2/6-311++G