Centro de Ciências Exatas e Tecnológicas
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/9791
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Resultados da Pesquisa
Item Effects of caffeine on the structure and conformation of DNA: A force spectroscopy study(International Journal of Biological Macromolecules, 2019-06-01) Moura, T. A.; Oliveira, L.; Rocha, M.S.Here, we use single molecule force spectroscopy performed with optical tweezers in order to investigate the interaction between Caffeine and the DNA molecule for various different concentrations of the alkaloid and under two distinct ionic strengths of the surrounding buffer. We were able to determine the mechanical changes induced on the double-helix structure due to Caffeine binding, the binding mode and the binding parameters of the interaction. The results obtained show that Caffeine binds to DNA by outside the double-helix with a higher affinity at lower ionic strengths. On the other hand, a considerable cooperativity was found only for sufficient high ionic strengths, suggesting that Caffeine may binding forming dimers and/or trimers along the double-helix under this condition. Finally, it was also shown that Caffeine stabilizes the DNA double-helix upon binding, preventing force-induced DNA melting.Item Biophysical characterization of the DNA interaction with the biogenic polyamine putrescine: a single molecule study(International Journal of Biological Macromolecules, 2018-02-26) Publio, B.C.; Moura, T.A.; Lima, C.H.M.; Rocha, M.S.We have performed a biophysical characterization, at single molecule level, of the interaction between the DNA molecule and the biogenic polyamine putrescine. By using force spectroscopy, we were able to monitor the complexes formation as putrescine is added to the sample, determining the mechanical properties of such complexes and the physicochemical (binding) parameters of the interaction for three different ionic strengths. In particular, it was shown that the behavior of the equilibrium binding constant as a function of the counterion concentration deviates from the prediction of the Record-Lohman model. The measured constants were (1.3 ± 0.2) × 10^5 M^- 1 for [Na] = 150 mM, (2.1 ± 0.2) × 10^5 M^- 1 for [Na] = 10 mM, and (2.2 ± 0.3) × 10^5 M^- 1 for [Na] = 1 mM. The cooperativity degree of the binding reaction, on the other hand, increases with the ionic strength. From these analysis, the DNA-putrescine binding mechanisms are inferred, and a comparison with results reported for ordinary bivalent ions like magnesium is performed. Such study provides new insights on the general behavior of the DNA interactions with biogenic polyamines.