PRESSURE-TUNING INFRARED SPECTRA OF THE THIAMINE ENZYME ACTIVE ALDEHYDE INTERMEDIATE 2-(ALPHA-HYDROXYCYCLOHEXYLMELHYL)THIAMINE CHLORIDE (HCMT-CENTER-DOT-HCL) AND ITS COMPLEX WITH ZINC(II), ZN(HCMT)CL-3

摘要

IR spectra of the protonated form of 2-(alpha-hydroxycyclohexymethyl)thiamine chloride (HCMT . HCl) and the zwitterionic zinc(II) complex, Zn(HCMT)CI3, have been recorded at room temperature and various pressures up to similar to 30 kbar. The majority of the peaks are blue shifted (towards higher wavenumbers) with increasing pressure; the nu(OH) and nu(NH) vibrations are red shifted, As for the closely related 2-(alpha-hydroxybenzyl)thiamine hydrochloride ligand and its metal complexes, the pyrimidine skeletal ring vibrations are quite pressure-sensitive (d nu/dP>0.50 cm(-1)/kbar). In solution, the pyrimidine and thiazolium rings of the HCMT ligand adopt an S conformation with respect to one another and this conformation is apparently retained in the solid-state, even at very high pressures, suggesting that its stability may be important in the enzymatic action of thiamine in the presence of divalent metal ions. [References: 25]