Poly -ethidium complex

Thermal denaturation - with poly[d(A-T)] -1- complex, behaviour similar to that with ethidium bromide. + 49... 

It should be noted that the H-3 shifts on proflavine complex formation (Figure 20) parallel those reported for ethidium bromide complex formation with poly(dA-dT) (11). 

In the center of the duplex shifts upfield by 0.15 ppm (Table VI, Figure 25) and the thymidine CH3-5 which Is directed towards the major groove shifts upfield by 0.1 ppm (Figure 29). It should be noted that such an upfield shift of the thymidine CH3-5 group was not observed in the intercalation complexes of ethidium (11), proflavine (25), terpyridylplatinum II (11) and nitroaniline dication with poly(dA-dT). The results require that at least one thymidine CH3-5 group project onto the periphery of the anthra-cycline ring system at the intercalation site. 

It has been shown that DNA intercalators (ethidium bromide and proflavine) form complexes with single-stranded DNA and homopolynucleotides [3]. It was of interest, therefore, to determine the effect of intercalators on the degradation of the homopolymer (ADP-ribose)jj by the poly (ADP-ribose) glycohydrolase. 

Patel, D. J. Canuel, L. L. Biphasic helix-coil transition of the ethidium bromide.poly(dA-dT) and the propidium diiodide.poly(dA-dT) complexes ... 

Ethidium bromide inhibits the T4 DNA ligase-catalyzed ligation of poly[d(AT)] with an ID50 of —4.3 p.M (13). The inhibition is not due to the interaction of EtBr with the enzyme per se, but to the drug-DNA binding (or intercalation) so that formation of the active DNA-Mg " -AMP-enzyme complex is impaired. 

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