Interaction of Ni(II)-ethylenediamine/histamine with histidylglycine and investigation of their DNA cleavage abilities

761-768The interaction of Ni(II)-ethylenediamine (en)/histamine(hist) with histidylglycine(his-gly) and their DNA cleavage abilities have been investigated. The stability constants for the Ni(II)-en-his-gly (1) and Ni(II)-hist-his-gly (2) complexes have been determined at 298.0 K and 0.10 M (KNO3) ionic strength. Both the 1:1:1 ternary complexes have been corroborated by species distribution curves and ESI-MS analysis. The complex geometries have been analyzed by UV-vis experiments and molecular mechanics simulations. The DNA binding abilities of these complexes have been established by UV-vis-absorption, thermal-denaturation and fluorescence spectroscopy. The intrinsic binding constants for the bound complexes, Ni(II)-en-his-gly:DNA and Ni(II)-hist-his-gly:DNA, have been determined to be 280 and 420 M-1 respectively. Gel-electrophoresis experiments reveal that 1 and 2 cleave supercoiled DNA (type-I) to the nicked-circular (type-II) form hydrolytically at physiological pH. A tentative mechanism is proposed for the cleavage

Gram-Scale Solution-Phase Synthesis of Heptapeptide Side Chain of Teixobactin

We report herein a scalable synthesis of linear heptapeptide side chain of the depsipeptide natural product teixobactin through solution phase. The synthesis of heptapeptide was achieved through an efficient coupling of suitably protected tripeptide and tetrapeptide comprising of three d-amino acids and four usual l-amino acid subunits.</jats:p