Presentation Title

Inhibition of Oxidative DNA Damage via Green Tea

Start Date

November 2016

End Date

November 2016

Location

HUB 379

Type of Presentation

Oral Talk

Abstract

Oxidative damage is involved in the formation of free radicals, which can cause various diseases. In DNA, this damage is observed primarily at guanine because it is the most easily oxidized base and one form of oxidative damage is DNA-protein crosslinking. Here, we examined which brands, conditions and concentrations of green tea are most effective in preventing oxidative DNA damage. Oxidation was effected by the flash-quench technique, a method that is used for guanine oxidation and that can induce DNA-protein crosslinking. In the flash quench technique, the intercalator, Ru(phen)2dppz2+[phen = phenanthroline, dppz = dipyridophenazine], is excited with a laser and gives an electron to the quencher, Co(NH3)5Cl2+ . The intercalator takes an electron from guanine, creating the guanine radical, which then reacts with protein. In our experiment, samples containing Ru(phen)2dppz2+,Co(NH3)5Cl2+, histone protein, calf thymus DNA and either water or green tea were irradiated for 0-4 minutes with blue laser light from a HeCd laser to effect guanine damage. The extent of crosslinking was determined by the chloroform extraction assay, whereby protein and DNA-protein crosslink is extracted away from unreacted DNA. Our results showed as the irradiation time increased, the absorption of free DNA decreased less in the presence of green tea, consistent with inhibition of DNA oxidation. In addition, agarose gel electrophoresis experiments of samples containing pUC19 DNA with tea that was stored at cold temperatures showed that the free DNA band persisted at dilutions of green tea up to 1:10000. Additionally, a pro-oxidative effect was observed at high tea concentrations. In future work, experiments will be carried out to determine a more accurate concentration range for the antioxidative effects of the green tea as well as examine the damage seen at high concentrations of tea; analogous experiments suggest that phenols could produce the inhibitory effect by reducing guanine radicals.

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Nov 12th, 11:00 AM Nov 12th, 11:15 AM

Inhibition of Oxidative DNA Damage via Green Tea

HUB 379

Oxidative damage is involved in the formation of free radicals, which can cause various diseases. In DNA, this damage is observed primarily at guanine because it is the most easily oxidized base and one form of oxidative damage is DNA-protein crosslinking. Here, we examined which brands, conditions and concentrations of green tea are most effective in preventing oxidative DNA damage. Oxidation was effected by the flash-quench technique, a method that is used for guanine oxidation and that can induce DNA-protein crosslinking. In the flash quench technique, the intercalator, Ru(phen)2dppz2+[phen = phenanthroline, dppz = dipyridophenazine], is excited with a laser and gives an electron to the quencher, Co(NH3)5Cl2+ . The intercalator takes an electron from guanine, creating the guanine radical, which then reacts with protein. In our experiment, samples containing Ru(phen)2dppz2+,Co(NH3)5Cl2+, histone protein, calf thymus DNA and either water or green tea were irradiated for 0-4 minutes with blue laser light from a HeCd laser to effect guanine damage. The extent of crosslinking was determined by the chloroform extraction assay, whereby protein and DNA-protein crosslink is extracted away from unreacted DNA. Our results showed as the irradiation time increased, the absorption of free DNA decreased less in the presence of green tea, consistent with inhibition of DNA oxidation. In addition, agarose gel electrophoresis experiments of samples containing pUC19 DNA with tea that was stored at cold temperatures showed that the free DNA band persisted at dilutions of green tea up to 1:10000. Additionally, a pro-oxidative effect was observed at high tea concentrations. In future work, experiments will be carried out to determine a more accurate concentration range for the antioxidative effects of the green tea as well as examine the damage seen at high concentrations of tea; analogous experiments suggest that phenols could produce the inhibitory effect by reducing guanine radicals.