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[Quenching of singlet oxygen with chlorophylls and porphyrins].

The rate constants (kox) of irreversible oxidation of chlorophylls and porphyrins by 1 delta g state of oxygen (1O2) have been determined. It has been shown that kox values are 1-5 orders of magnitude lower than the values of rate constants of quenching 1O2 (kq) with the same pigments. The correlation between kox and kq has been found. Its analysis allowed to conclude that oxidation proceeds via intermediate formation of a charge transfer complex between the pigments and 1O2. A kinetic scheme of the processes leading to physical and chemical quenching 1O2 with chlorophylls and porphyrins is proposed, its mathematical analysis is carried out. The results of this analysis can be used for a search of substances capable of effective quenching 1O2 without destruction of the quenchers. It is concluded that chlorophylls protect photosynthetic membranes from the destruction by 1O2, and some synthetic metal-porphyrins can be used as good protectors of different systems against photooxidation.

Chlorophyll↗
PubMed1993

Singlet oxygen-induced DNA damage: product analysis, studies of biological consequences and characterization of mutations.

The DNA lesions induced by free 1O2 and the biological and mutagenic consequences of 1O2-induced DNA damage have been studied. Using anion exchange HPLC, reverse-phase HPLC with electrochemical detection and 32P-postlabelling methods, we have shown that 1O2 reacts with 2'-deoxyguanine 3'-monophosphate (dGp) but not with any other dNp. Reaction with dGp yields a large number of products; one minor product was identified as 7-hydro-8-oxo-2'-deoxyguanosine 3'-monophosphate (8-oxo-dGp), and a second tentatively as a formamidopyridine derivative of dGp. 8-Oxo-dGp was also found after reaction of 1O2 with single-stranded (ss) DNA, double-stranded (ds) DNA or an oligonucleotide (16-mer) having one G. With the oligonucleotide we found a second unidentified reaction product. With ss DNA, 8-oxo-dG was a much more prominent product than in the reaction of 1O2 with free dGp and the yield was about eight-fold higher than with ds DNA. This agrees with our finding that ss M13 DNA is at least 100-fold more sensitive than ds M13 DNA to biological inactivation by 1O2. The inactivation of ss M13 DNA must be largely due to 1O2-induced lesions other than 8-oxo-dG. In agreement with the observed preferential reaction of 1O2 with dG, most of the mutations induced by 1O2 in ss or ds M13mp10 DNA occurred at a G or G/C basepair, respectively. A preference for G(C) to T(A) transversions was observed for which 8-oxo-dG might have been responsible. In ss DNA, a significant number of mutations are characterized by the fact that a G is deleted.

Bacteriophage M13↗
PubMed1995

Molecular modeling of singlet-oxygen binding to anthraquinones in relation to the peroxidating activity of antitumor anthraquinone drugs.

Anthraquinone derivatives are important anti-cancer drugs possessing, however, undesirable peroxidating and, in consequence, cardiotoxic properties. This results from the mediation by these compounds of the one-electron reduction processes of the oxygen molecule, which produces the highly toxic superoxide anion radical and other active oxygen species. This article summarizes the results of our studies on the molecular aspects of the mechanism of anthraquinone-mediated peroxidation which were carried out using enzymatic-assay, electrochemical, and quantum-mechanical methods.

Anthraquinones↗
PubMed1999

Novel Fluorescent Probes for Singlet Oxygen.

The first fluorescent chemical traps for (1)O(2) have been developed. DPAXs react specifically with (1)O(2) to yield the corresponding endoperoxides, DPAX-EPs (see scheme; X = H, Cl, F). DPAXs scarcely fluoresce, while DPAX-EPs are strongly fluorescent. Since the fluorescence of these probes is unaffected by H(2)O(2), superoxide, and nitric oxide, they are useful for the selective detection of (1)O(2) in biological systems.

Journal Article↗