AbstractThe Raman spectra of aqueous mixtures of glutathione (GSH) and methylmercury(II) were obtained at various [GSH]/[CH3Hg(II)] ratios and pH conditions. The results show that the favored step in the complexation of these species is through the substitution of the proton on the thiol group of GSH by a CH3Hg+ion. Coordination of a second methylmercury ion on to the sulfur atom is also believed to occur extensively in acidic solutions, giving the charged complex GS(HgCH3)2+. The decrease in the concentration of this species with increasing pH is partly compensated for by complexation through substitution of a proton on the protonated amino group of GSH, a process which is favored in basic solutions. A factor analysis, based on Raman spectra of various mixtures studied under different pH conditions, has shown that these three types of complexation accounts for nearly all of the interactions which take place between glutathione and methylmercury.