Analytical methods to determine the comparative DNA binding studies of curcumin-Cu(II) complexes.

DNA interaction studies of two mononuclear [1:1(1); 1:2(2)] copper(II) complexes of curcumin have been studied. The interaction of these complexes with CT-DNA has been explored by physical methods to propose modes of DNA binding of the complexes. Absorption spectral titrations of complex 1 with CT-DNA shows a red-shift of 3 nm with the DNA binding affinity of K(b), 5.21×10(4)M(-1) that are higher than that obtained for 2 (red-shift, 2 nm; K(b), 1.73×10(4)M(-1)) reveal that the binding occurs in grooves as a result of the interaction is via exterior phosphates. The CD spectra of these Cu(II) complexes show a red shift of 3-10nm in the positive band with increase in intensities. This spectral change of induced CD due to the hydrophobic interaction of copper complexes with DNA is the characteristic of B to A conformational change. The EB displacement assay also reveals the same trend as observed in UV-Vis spectral titration. The addition of complexes 1 and 2 to the DNA bound ethidium bromide (EB) solutions causes an obvious reduction in emission intensities indicating that these complexes competitively bind to DNA with EB. The positive shift of both the E(pc) and E(0)' accompanied by reduction of peak currents in differential pulse voltammogram (DPV), upon adding different concentrations of DNA to the metal complexes, are obviously in favor of strong binding to DNA. The super coiled plasmid pUC18 DNA cleavage ability of Cu(II) complexes in the presence of reducing agent reveals the single strand DNA cleavage (ssDNA) is observed. The hydroxyl radical (HO()) and the singlet oxygen are believed to be the reactive species responsible for the cleavage.

Curdlan complexes as a potential food-grade delivery system: genistein case study.

Complexes of curdlan and genistein were prepared using four different methods. The total amount of genistein in curdlan-genistein complexes prepared at 40 degrees C (system I) was significantly higher (2.3 mg/100 mg dry matter) than that in other systems studied: curdlan-genistein complexes prepared at 60 degrees C (system II; 1.8 mg/100 mg dry matter); curdlan-genistein gel complexes (system III; 1.0 mg/100 mg dry matter); and curdlan-genistein dimethyl sulfoxide complexes (system IV; 1.8 mg/100 mg dry matter). x-ray diffraction results indicate that complexation of curdlan with genistein changes the crystalline nature of the pure components. Particle size analysis, atomic force microscopy and scanning electron microscopy imaging of curdlan-genistein complexes showed strong difference in particle size, surface and distribution in comparison with pure curdlan, confirming our assumption of a molecular interaction between curdlan and genistein and the formation of a new structure, which was revealed at the nanoscale level. All the curdlan-genistein complexes showed prolonged genistein release of up to 72 h, enhanced upon enzymatic digestion of curdlan by lyticase, thus opening the possibility of release regulation by the incorporation of lyticase in the delivery system. It is therefore suggested that the complexes could be used as a delivery system for the protection and slow release of genistein in the digestive tract.

DNA assisted fragmentation of nickel nanoparticle clusters and their spectral properties.

Nickel nanoparticle (NiNP) clusters in the range of 60-70 nm size on interaction with herring-sperm DNA (B-DNA) form a self-assembled duplex helix DNA structure with fragmented NiNPs as small as 5-15 nm, as evident from atomic force microscopic studies. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images also corroborate the findings. The properties of these self-assembled NiNPs-DNA structures have been further investigated by UV-visible, emission and circular dichroic (CD) spectral studies.