The exploration of efficient DNA intercalative agents (intercalators) is essential for understanding DNA scission, repair, and signal transduction. In this work, we explored systematically the graphene oxide (GO) interaction with DNA molecules using fluorescence spectroscopic (FL) and circular dichroism (CD) studies, gel electrophoresis, and DNA thermal denaturation. We demonstrated that the GO nanosheets could intercalate efficiently into DNA molecules. Significantly, we illustrated that the scission of DNA by GO sheets combining with copper ions could take place pronouncedly. The scission of DNA by the GO/Cu(2+) system is critically dependent on the concentrations of GO and Cu(2+) and their ratio. DNA cleavage ability exhibited by the GO with several other metal ions and the fact that GO/Cu(2+)-cleaved DNA fragments can be partially relegated suggest that the mechanism of DNA cleavage by the GO/metal ion system is oxidative and hydrolytic. The result reveals that the GO/Cu(2+) could be used as a DNA cleaving system that should find many practical applications in biotechnology and as therapeutic agents.
A facile activity assay for an H + -coupled transporter using florescent probes was developed with an H + -coupled manganese transporter (MntH) as a model. Making use of coupled-proton transport, the transport activity (H + /Mn 2+ cotransport) can be directly determined via fluorescence intensity changes of the probe, 5-(and-6)carboxyfluorescein (5(6)-FAM). The approach of using highly sensitive fluorescence probes provides a more simple and convenient assay method for the determination of proton-coupled metal-ion uptake by transporters.
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