Biologically active methionine and its proto-lytic properties

The proto-lytic properties of methionine aqueous solutions have been studied by means of ph-metric titration method in the temperature range from 293.16 to 328.16 K at a constant ionic strength of solution 0.1 mol/l (Na(H)CIO₄). The presence of interionic forces of attraction and repulsion of basic particles affects the values of ionization constants of methionine. It has been shown that with temperature increasing, the formation processes of cationic, zwitterionic, and anionic forms of methionine shift to the acidic region or lower ph values. The curves of the undissociated and dissociated forms of methionine in the distribution diagram are on the ph scale to the left, and the values of pK₁ and pK₂ change. The presence of interionic forces of attraction and repulsion of basic particles affects the values of the ionization constants of methionine. (author)