The interaction of DAPI with natural and synthetic polydeoxynucleotides of different base content and sequences was studied with circular dichroism, ultracentrifugation, viscosity and calorimetry. All the polymers show two types of binding. The strength of the interaction and its resistance to ionic strength are related to the content of AT clusters in the chain. On the other hand, sedimentation measurements rule out an intercalation mechanism. A model of DAPI interaction with DNA, similar to that displayed by distamycin and netropsin, is proposed.

Anthocyanins, colored flavonoids, are water-soluble pigments present in the plant kingdom; in fact they are secondary plant metabolites responsible for the blue, purple, and red color of many plant tissues. Present in beans, fruits, vegetables and red wines, considerable amounts of anthocyanins are ingested as constituents of the human diet (180-215 mg daily). There is now increasing interest in the in vivo protective function of natural antioxidants contained in dietary plants against oxidative damage caused by free radical species. Recently, the antioxidant activity of phenolic phytochemicals, has been investigated. Since the antioxidant mechanism of anthocyanin pigments is still controversial, in the present study we evaluated the effects of cyanidin and cyanidin 3-O-beta-D-glucoside on DNA cleavage, on their free radical scavenging capacity and on xanthine oxidase activity. Cyanidin and cyanidin 3-O-beta-D-glucoside showed a protective effect on DNA cleavage, a dose-dependent free radical scavenging activity and significant inhibition of XO activity. These effects suggest that anthocyanins exhibit interesting antioxidant properties, and could therefore represent a promising class of compounds useful in the treatment of pathologies where free radical production plays a key role.

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The antioxidant properties of propofol can be partially attributed to its scavenging effect on peroxynitrite as well as to its ability to increase HO-1 expression at higher concentrations, a property that might be relevant to neuroprotection during anesthesia.

Steady-state and dynamic fluorescence measurements have been performed on DAPI in solution and in complexes formed with a number of synthetic and natural polydeoxynucleotides. The decay of DAPI in buffer at pH 7 was decomposed using two exponentials having lifetime values of approximately 2.8 ns and 0.2 ns. The double exponential character of the decay was maintained over a large pH range from 3 to 9. At pH 1 the short component dominated, whereas at pH 12, only the long component was detectable. Two distinct spectra were associated with the two lifetime components; the short component was shifted to the red. The short lifetime component occurs in the presence of water. In water the excitation spectra depended on the emission wavelength and there was no viscosity dependence of the two forms. To explain these results we propose that there is a ground state conformer in which preferential solvation of the indole ring allows proton transfer in the excited state. DAPI complexed with polydeoxynucleotides retained most of the features of the decay of DAPI in solution. However, the complexes with fully AT-containing polymers stabilized the longer lifetime form of DAPI because the stronger binding enhanced solvent shielding. A gradual increase of the short lifetime component, which monitors dye solvent exposure, was obtained as the AT content was decreased. For polyd(GC) the decay was similar to that of free DAPI.