Guanine quadruplex (G-quadruplex) structures are formed by guanine-rich oligonucleotides. Because of their in vivo and in vitro importance, numerous studies have been demonstrated that the structure and stability of the G-quadruplex are dependent on the sequence of oligonucleotide and environmental conditions such as existing cations. Previously, we quantitatively investigated the divalent cation effects on the antiparallel G-quadruplex of d(G4T4G4), and found that Ca2+ induces a structural transition from the antiparallel to parallel G-quadruplex, and finally G-wire formation. In the present study, we report in detail the kinetic and thermodynamic analyses of the structural transition induced by Ca2+ using stopped-flow apparatus, circular dichroism, size-exclusion chromatography (SEC) and atomic force microscopy. The quantitative parameters showed that at least two Ca2+ ions were required for the transition. The kinetic parameters also indicated that d(G4T4G4) underwent the transition through multiple steps involving the Ca2+ binding, isomerization and oligomerization of d(G4T4G4). The parallel-stranded G-wire structure of d(G4T4G4), which is a well controlled alignment of numerous DNA strands with G-quartets, as the final product induced by Ca2+, was observed using SEC and atomic force microscopy. These results provide insight into the mechanism of the structural transition and G-wire formation and are useful for constructing a nanomaterial regulated by Ca2+.

No abstract

These data indicate that gene transfer of Smad7 prevents UUO-induced renal fibrosis, suggesting that Smad7 may be applicable for the treatment of renal fibrosis. In vivo electroporation of adenovirus may be a powerful tool for gene delivery in renal tissue.

Radiocesium interception potential (RIP), a quantitative index of a frayed edge site of micaceous minerals, was investigated on test clay minerals (illite, kaolinite, montmorillonite and vermiculite) and soil clays formed under different pedogenetic conditions in the Kinki district of Japan and in northern Thailand to elucidate the effect of pedogenetic weathering on the amount of frayed edge site of micaceous minerals. ) compared with illitic minerals (4.3 mol kg -1 in silt size; 11.8 mol kg -1 in clay size) suggested that the frayed edge site increased as the expanded layer formed in the micaceous minerals. In northern Thailand soil clays, the absence of a vermiculitic expanded layer was indicated. Periodic wet-dry conditions may restrict K depletion from micaceous minerals in the region. It is concluded that micaceous minerals were weathered without layer expansion and, therefore, the amount of the frayed edge site was regulated by the content of micaceous minerals in northern Thailand. In Japanese soil clays, large RIP values were found in the EB and Bs horizons of a Podzodic profile (SW1), which had large vermiculitic expanded layers like the test vermiculite. However, the RIP values drastically decreased from the Bs to E horizon, maintaining a high vermiculitic layer charge. Thus, intensive weathering in highly acidic soils in Japan might reduce the frayed edge site.