A Spectrophotometric Study of the Complexation of Magnesium(II) with a Number of Amino Acids in Aqueous Solutions

A spectrophotometric study of the complexation of magnesium(II) with glycine, L-aspartic, and L-glutamic amino acids in an aqueous solution at 298.15 K was carried out. The method used to this end was based on taking the spectra of mixtures of magnesium(II) with amino acids of various concentrations and their subsequent processing by the multiple linear regression (MLR) technique. For the working solutions, the absorbance was determined over a broad wavelength range of 190-370 nm; next, wavelengths for determination of the equilibrium concentrations of the reaction participants with the smallest relative errors were chosen using special software (DefMix, KOEFF_COUNTER, CONCENTR_COUNTER). For each complex, those wavelengths were selected for which the relative determination errors were less than 5%. Using these wavelengths, the overall stability constants of the complexes and the Gibbs energies of complexation were calculated. The differences in the obtained values of the stability constants of the magnesium(II) complexes with the amino acids were explained, and factors affecting their stability were identified. For the magnesium-glutamic acid system, log K was estimated at 2.02, and the Gibbs energy of complexation, at -11.51 kJ/mol, for the magnesium-aspartic acid system, at 2.61 and -14.87 kJ/mol, respectively, and for the magnesium-glycine system, at 3.59 and -20.05 kJ/mol, respectively. Performing this work will allow expanding the database on the interaction of magnesium(II) with amino acids. The results obtained can be used in studies of various biomineralization processes in human body, as well as in the creation of medications intended for targeted exposure.