Selective targeting of DNA for cleavage within DNA-histone assemblies by a spermine-[CpW(CO)3Ph]2 conjugate.

In contrast to the histone-modifying action of other complexes of the type CpML(n)R, the compound obtained by linking the phenyl rings of two CpW(CO)(3)Ph moieties to the DNA-binding agent spermine selectively cleaves DNA in DNA-histone assemblies.

Photoreactions of riboflavin with spermine and their role in tryptophan photoconsumption induced by riboflavin.

The influence of spermine (Spr) on riboflavin (Rb) and riboflavin-tryptophan (Rb-Trp) solutions irradiated at 450 nm under aerobic and anaerobic conditions was studied. In both systems, it is shown that Spr interacts with 3Rb probably giving spermine-derived and flavin-derived radicals. In the presence of oxygen, modified Rb is regenerated with the simultaneous production of the active oxygen species O2.- and/or HO2.. The addition of Spr to the Rb-Trp system under aerobic conditions leads to a small protection of Trp consumption, although oxygen consumption is increased. This small protection arises as a consequence of competitive interaction of Trp and Spr with 3Rb. The competition of Spr and oxygen for 3Rb could also explain the autocatalytic oxygen consumption observed in the presence of the amine. Under anaerobic conditions Spr produces a larger protection of Trp consumption, which is compatible with the larger Rb triplet lifetime expected under these conditions.