Ternary complexes of cobalt cysteinylglycine with histidylserine and histidylphenylalanine-stabilities and DNA cleavage properties

Abstract

Interaction of cobalt cysteinylglycine with histidylserine and histidylphenylalanine was investigated in a 1 : 1 : 1 ratio at 35°C and 0⋅10 mol dm -3 ionic strength. Their stabilities and geometries were determined. Their DNA binding and cleavage properties were investigated. The intrinsic binding constants (K b ) for DNA bound 1 and 2 (3⋅03 × 10 3 M -1 for 1 and 3⋅87 × 10 3 M -1 for 2) were determined. Even though the negative charge on the complexes reduced their affinity for DNA, there was an enhancement of binding through specificity. The degradation of plasmid DNA was achieved by cobalt dipeptide complexes [Co II (CysGly)(HisSer)] (1) and [Co II (CysGly)(HisPhe)] (2). Cleavage experiments revealed that 1 and 2 cleave supercoiled DNA (form I) to nicked circular (form II) through hydrolytic pathway at physiological pH. The DNA hydrolytic cleavage rate constants for complexes 1 and 2 were determined to be 0⋅62 h -1 , for 1 and 0⋅38 h -1 for 2 respectively.

Gel-Electrophoresis and Its Applications

“…We have been using this technique for some time in the development of new metallonucleases as small molecular models for DNA cleavage at physiological conditions (Reddy, P. R. et.al, 2004(Reddy, P. R. et.al, -2011. Since DNA cleavage is a biological necessity, these small molecular models have provided much of our most accurate information about nucleic acid binding specificity.…”