Conformational changes in serine on methylmercury complexation

Abstract

The CH3Hg+ cation forms a zwitterionic complex CH3Hg[HOCH2CH(NH2)CO2—N,O,O] with serine in aqueous solution. X-ray diffraction (P212121, a = 5.821, b = 8.052, c = 14.307 Å, R = 0.021) shows that mercury is linearly bonded to the NH2 end of the amino acid, whereas one carboxylate oxygen and the side-chain hydroxyl group establish secondary Hg—O bonds. Coordination leads to characteristic changes in the infrared and Raman spectra of serine. From the 1H and 13C nmr spectra, N-coordination is found to be retained in aqueous solution, whereas the ligand conformation observed in the solid accounts for 76% of the conformer distribution.