Demonstration of Z-d(5BrCGAT5BrCG) and B-d(CGCGATCGCG) form crystal structures in DNA-cobalt hexammine complexes by Kr 647.1 nm excitation of Raman spectra

Surface-enhanced Raman spectroscopy for real-time monitoring of reactive oxygen species-induced DNA damage and its prevention by platinum nanoparticles

We have successfully demonstrated the potential of surface-enhanced Raman spectroscopy (SERS) in monitoring the real time damage to genomic DNA. To reveal the capabilities of this technique, we exposed DNA to reactive oxygen species (ROS), an agent that has been implicated in causing DNA double-strand breaks, and the various stages of free radical-induced DNA damage have been monitored by using SERS. Besides this, we showed that prompt DNA aggregation followed by DNA double-strand scission and residual damage to the DNA bases caused by the ROS could be substantially reduced by the protective effect of Pt nanocages and nearly cubical Pt nanopartcles. The antioxidant activity of Pt nanoparticles was further confirmed by the cell viability studies. On the basis of SERS results, we identified various stages involved in the mechanism of action of ROS toward DNA damage, which involves the DNA double-strand scission and its aggregation followed by the oxidation of DNA bases. We found that Pt nanoparticles inhibit the DNA double-strand scission to a significant extent by the degradation of ROS. Our method illustrates the capability of SERS technique in giving vital information about the DNA degradation reactions at molecular level, which may provide insight into the effectiveness and mechanism of action of many drugs in cancer therapy.

Study of the interaction of hexa-amine cobalt (III) ion with DNA by a resonance light scattering technique and its analytical application

The effect of hexa-amine cobalt cations on the DNA condensation in aqueous solution was investigated by resonance light scattering (RLS). When the relative concentration of hexa-amine cobalt (III) cations to DNA is in the appropriate range, the cations will induce DNA condensation and aggregation, which results in a strong RLS spectrum characterized by a peak at 290.0 nm. The RLS technique is a powerful tool for monitoring DNA condensation and, under optimal conditions, the enhanced RLS intensity at 290.0 nm was proportional to the concentration of DNA in the range 0.01-6.0 microg/mL. Based on this, a sensitive and convenient analysis method for the microdetermination of DNA was established. The detection limit (3 s) of calf thymus DNA by the proposed method is 1.9 ng/mL and few substances interfere in the DNA determination.

Crystal structure of d(AGGBrCATGCCT): implications for cobalt hexammine binding to DNA

The crystal structure of the DNA decamer d(AGGBrCATGCCT) has been determined to a resolution of 2.0 A and R factor of 19.6%. Crystals of d(AGGBrCATGCCT) were grown in the presence of cobalt hexammine but no cobalt hexammine ions are bound to the DNA structure. This contrasts with the recently determined crystal structure of d(AGGCATGCCT) which has a similar DNA conformation and cobalt hexammine ions bound directly to the DNA. Comparison with the structure of d(AGGCATGCCT) and appreciation of the crystal packing of this sequence leads to an understanding of how cobalt hexammine binding to DNA occurs and its role in determining DNA conformation.