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The cleavage of plasmid DNA (pUB110) by several square planar nickel(II) complexes in the presence of either magnesium monoperoxyphthalic acid (MPPA) or iodosylbenzene was investigated. At 25°C and near neutral pH, Ni(salen) (100 μM) or Ni(CR) 2+ (100 μM) promoted complete conversion of supercoiled plasmid to the nicked circular form in 5 min with iodosylbenzene (0.1 g/ml) as oxidant or in 2.5 h with MPPA (1 mM) as oxidant (salen = bis(salicylaldehyde)ethylenediimine, CR = 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca- 1(17),2,11,13,15-pentaene). No cleavage was observed under similar conditions with Ni(cyclam) 2+ , Ni(dioxocyclam), Ni(TPP) or Ni(NO 3 ) 2 (cyclam = 1,4,8,11-tetraazacyclotetradecane, dioxocyclam = 1,4,8,11-tetraazacyclotetradecane- 5,7-dione, TPP=5,10,15,20-tetraphenyl-21 H ,23 H -porphine). Possible roles for the nickel complexes in promoting DNA cleavage are discussed.

The cleavage of plasmid DNA (pUB110) by several square planar nickel(II) complexes in the presence of either magnesium monoperoxyphthalic acid (MPPA) or iodosylbenzene was investigated. At 25°C and near neutral pH, Ni(salen) (100 μM) or Ni(CR) 2+ (100 μM) promoted complete conversion of supercoiled plasmid to the nicked circular form in 5 min with iodosylbenzene (0.1 g/ml) as oxidant or in 2.5 h with MPPA (1 mM) as oxidant (salen = bis(salicylaldehyde)ethylenediimine, CR = 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca- 1(17),2,11,13,15-pentaene). No cleavage was observed under similar conditions with Ni(cyclam) 2+ , Ni(dioxocyclam), Ni(TPP) or Ni(NO 3 ) 2 (cyclam = 1,4,8,11-tetraazacyclotetradecane, dioxocyclam = 1,4,8,11-tetraazacyclotetradecane- 5,7-dione, TPP=5,10,15,20-tetraphenyl-21 H ,23 H -porphine). Possible roles for the nickel complexes in promoting DNA cleavage are discussed.

Role d'espaceur inerte des motifs chlorure de vinylidene qui diminuent les associations intramoleculaires entre les dipoles carbonyl des motifs MMA du copolymere. Stabilite thermique minimale des copolymeres lorsque le nombre de motifs MMA et VDC adjacents est maximal; degradation thermique via une cyclisation intramoleculaire et perte de HCl pour donner une lactone a 5 chainons insatures