Microcalorimetric studies on the DNA scission by (1,10-phenanthroline) copper

Using the LKB - 2277 now microcalorimeter (Bioactivity Monitor) and the LKB - 2107 batch microcalorimeter, the scission of calf thymus ds DNA by the m ixture of (1,10 - phenanthroline) copper (II) [(phen)(2)Cu2+], mercaptoetha nol and O-2 has been studied. The overall reaction of this DNA cleavage has been established as a faster, exothermic and enthalpy - driven reaction, b ut the earlier stage of this cleavage is a fast endothermic process. The ov erall molar reaction enthalpy and the molar reaction enthalpy of the earlie r stage of this cleavage have been measured as Delta(r)H(m,3) = - 35.1 kJ . mol(-1) and Delta(r)H(m,1) = 7.29 kJ . mol(-1), respectively, at 310.15K a nd pH 7.0. DNA backbone - cleavage has also been observed in agarose gel el ectrophoresis.