A theoretical elucidation of coordination properties of histidine and lysine to Mn2+

Present account is an elucidation of interaction between histidine and lysine with Mn2+ in the gas phase by quantum chemical calculations. In addition, side chain effects of these amino acids on relative stability of different coordination modes have been considered by theoretical methods. Three types of complexation mode have been considered: (i) three dentate chelation of neutral amino acids; (ii) two dentate chelation of neutral amino acids; (iii) chelation of amino acids to metal ion in zwitterionic forms. Structure and vibrational frequencies have been determined by B3LYP method. Energy calculations are carried out in CCSD(T) level. For both Mn2+–Histidine and Mn2+–Lysine systems, the most stable structure resulted from interaction of neutral amino acids with metal cation via two amino groups and carbonyl oxygen while the complexes ground electronic state is determined as 6A. This is in contrast to Mn2+–Glycine system in which the most stable structure resulted from interaction of zwitterionic amino acid with metal ion.

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► Interaction between histidine and lysine with Mn2+ in the gas phase by quantum chemical calculations.
► Three types of complexation mode have been considered: (i) three dentate chelation of neutral amino acids; (ii) two dentate chelation of neutral amino acids; (iii) chelation of amino acids to metal ion in zwitterionic forms.
► The most stable structure resulted from interaction of neutral amino acids with metal cation via two amino groups and carbonyl oxygen.