Michael A. Terzidis

Bio: Michael A. Terzidis is an academic researcher from International Hellenic University. The author has contributed to research in topics: Chromone & One-pot synthesis. The author has an hindex of 15, co-authored 55 publications receiving 682 citations. Previous affiliations of Michael A. Terzidis include Aristotle University of Thessaloniki & New York University.

Purine 5′,8-cyclonucleoside lesions: chemistry and biology

Abstract: 5′,8-Cyclo-2′-deoxyadenosine and 5′,8-cyclo-2′-deoxyguanosine in their 5′R and 5′S diastereomeric forms are tandem-type lesions observed among the DNA modifications and identified in mammalian cellular DNAin vivo. These lesions result from the chemistry of the C5′ radicals generated by the attack of HO˙ radicals to 2-deoxyribose units. Quantitative determination of these lesions in biological samples as biomarkers of free radical damage is a challenge. Results reported for irradiated samples of calf thymus DNA have been critically reviewed, underlining the need of further research for the potential involvement of these lesions in human health (76 references).

Structural basis for the recognition of diastereomeric 5′,8-cyclo-2′-deoxypurine lesions by the human nucleotide excision repair system

Abstract: The hydroxyl radical is a powerful oxidant that generates DNA lesions including the stereoisomeric R and S 5',8-cyclo-2'-deoxyadenosine (cdA) and 5',8-cyclo-2'-deoxyguanosine (cdG) pairs that have been detected in cellular DNA. Unlike some other oxidatively generated DNA lesions, cdG and cdA are repaired by the human nucleotide excision repair (NER) apparatus. The relative NER efficiencies of all four cyclopurines were measured and compared in identical human HeLa cell extracts for the first time under identical conditions, using identical sequence contexts. The cdA and cdG lesions were excised with similar efficiencies, but the efficiencies for both 5'R cyclopurines were greater by a factor of ∼2 than for the 5'S lesions. Molecular modeling and dynamics simulations have revealed structural and energetic origins of this difference in NER-incision efficiencies. These lesions cause greater DNA backbone distortions and dynamics relative to unmodified DNA in 5'R than in 5'S stereoisomers, producing greater impairment in van der Waals stacking interaction energies in the 5'R cases. The locally impaired stacking interaction energies correlate with relative NER incision efficiencies, and explain these results on a structural basis in terms of differences in dynamic perturbations of the DNA backbone imposed by the R and S covalent 5',8 bonds.

5',8-Cyclopurine Lesions in DNA Damage: Chemical, Analytical, Biological, and Diagnostic Significance.

Abstract: Purine 5',8-cyclo-2'-deoxynucleosides (cPu) are tandem-type lesions observed among the DNA purine modifications and identified in mammalian cellular DNA in vivo. These lesions can be present in two diasteroisomeric forms, 5'R and 5'S, for each 2'-deoxyadenosine and 2'-deoxyguanosine moiety. They are generated exclusively by hydroxyl radical attack to 2'-deoxyribose units generating C5' radicals, followed by cyclization with the C8 position of the purine base. This review describes the main recent achievements in the preparation of the cPu molecular library for analytical and DNA synthesis applications for the studies of the enzymatic recognition and repair mechanisms, their impact on transcription and genetic instability, quantitative determination of the levels of lesions in various types of cells and animal model systems, and relationships between the levels of lesions and human health, disease, and aging, as well as the defining of the detection limits and quantification protocols.

One-pot synthesis of functionalized spirobenzofuranones via MCR involving 3-cyanochromones.

Abstract: Another aspect concerning chromone chemistry leading to the one-pot synthesis of functionalized novel spirobenzofuranones has been described. The synthesis involves reaction of the zwitterionic intermediates formed by the 1:1 interaction between isocyanides and acetylenecarboxylates with 3-cyanochromones, whereupon through an unexpected and unprecedented reaction of the chromone moiety the isolated benzofuranones are formed. The regioselectivity of the reaction was investigated by DFT calculations. The geometries of the intermediates, transition structures, and intermediate products, leading to the final products, were optimized using the B3LYP functional with the 6-31G(d) basis set. The structures of the products were elucidated by 1D and 2D NMR experiments. Full assignment of all (1)H and (13)C NMR chemical shifts has been achieved. A plausible mechanistic rationale is proposed.

One-pot synthesis of chromenylfurandicarboxylates and cyclopenta[b]chromenedicarboxylates involving zwitterionic intermediates. A DFT investigation on the regioselectivity of the reaction.

Abstract: The reaction of 1:1 zwitterionic intermediates generated in situ from either tert-butylisocyanide or cyclohexylisocyanide and acetylenedicarboxylates with 3-formylchromones is described, whereupon ...

DNA Base Damage by Reactive Oxygen Species, Oxidizing Agents, and UV Radiation

Abstract: Emphasis has been placed in this article dedicated to DNA damage on recent aspects of the formation and measurement of oxidatively generated damage in cellular DNA in order to provide a comprehensive and updated survey. This includes single pyrimidine and purine base lesions, intrastrand cross-links, purine 5',8-cyclonucleosides, DNA-protein adducts and interstrand cross-links formed by the reactions of either the nucleobases or the 2-deoxyribose moiety with the hydroxyl radical, one-electron oxidants, singlet oxygen, and hypochlorous acid. In addition, recent information concerning the mechanisms of formation, individual measurement, and repair-rate assessment of bipyrimidine photoproducts in isolated cells and human skin upon exposure to UVB radiation, UVA photons, or solar simulated light is critically reviewed.

Mechanisms of free radical-induced damage to DNA

Abstract: Endogenous and exogenous sources cause free radical-induced DNA damage in living organisms by a variety of mechanisms. The highly reactive hydroxyl radical reacts with the heterocyclic DNA bases and the sugar moiety near or at diffusion-controlled rates. Hydrated electron and H atom also add to the heterocyclic bases. These reactions lead to adduct radicals, further reactions of which yield numerous products. These include DNA base and sugar products, single- and double-strand breaks, 8,5′-cyclopurine-2′-deoxynucleosides, tandem lesions, clustered sites and DNA-protein cross-links. Reaction conditions and the presence or absence of oxygen profoundly affect the types and yields of the products. There is mounting evidence for an important role of free radical-induced DNA damage in the etiology of numerous diseases including cancer. Further understanding of mechanisms of free radical-induced DNA damage, and cellular repair and biological consequences of DNA damage products will be of outmost importan...

Chromone: A Valid Scaffold in Medicinal Chemistry

Abstract: This work was supported by the Foundation for Science and Technology (FCT), Portugal (projects PTDC/QUI-QUI/113687/2009 and PEst-C/QUI/UI0081/2013). A.G. (SFRH/BD/43531/2008) and M.J.M. (SFRH/BD/61262/2009) thank FCT for grants.