Nucleic acids symposium series (2004)最新文献

Palladium on carbon-ethylenediamine complex [Pd/C(en)] catalyzed deuteration of N(6)-benzyladenine-d(5), which is a plant growth regulator, to introduce 5 deuterium atoms, while use of Pd/C as a catalyst led to a complete removal of N(6)-benzyl group. The corresponding deuterated N(6)-benzyladenine was successfully used as a surrogate compound for the quantitative analysis of residual benzyladenine in crops using LC/MS/MS.

The DNA ternary complexes with carboxymethyl poly(L-histidine) (CM-PLH) and poly(ethylenimine) (PEI) have released the DNA binary complexes with PEI by the protonation of CM-PLH at endosomal/lysosomal pH. The dissociation of the CM-PLH from the CM-PLH/PEI/DNA ternary complexes is proved by the fluorescence resonance energy transfer (FRET) analysis between the CM-PLH and PEI. The resulting PEI/DNA binary complexes easily released DNA, as compared with the CM-PLH/PEI/DNA ternary complexes, which was examined by competitive exchange with dextran sulfate. The release of the DNA binary complexes from the ternary complexes is promising mechanism for higher transfection activity by the CM-PLH/PEI/DNA ternary complexes.

With an aim to develop a new approach to synthesize 4'-substituted nucleosides, reactions of thymidine derivatives having a benzenesulfonyl leaving group at the 4'-position with organosilicon and organoaluminum reagents were investigated. Two substrates 4alpha (alpha-L-isomer) and 4 beta (beta-D-isomer) were prepared for this purpose. Although reaction of 4alpha with organosilicon reagents gave preferentially the 4'-substituted (allyl and N(3)) beta-D-nucleoside, its reaction with AlMe(3) gave the 4'-methyl-alpha-L-thymidine as the major product. On the other hand, the substrate 4beta, upon reacting with AlMe(3), furnished the desired 4'-methylthymidine exclusively in high yield.

We report the synthesis and metal ion-binding properties of DNA duplexes containing 5-substituted uracil ((X)U) pairs, such as 5-bromouracil, 5-fluorouracil and 5-cyanouracil pairs. Thermal denaturation studies of these modified DNA duplexes revealed that the DNA duplexes were stabilized in the presence of Hg(II) ions in acidic and neutral solutions. On the other hand, the duplexes were stabilized in the presence of Hg(II) and Ag(I) ions. These results indicated that (X)U-Hg(II)-(X)U complex was formed in the acidic and neutral solutions, then, in the basic solutions (X)U-Ag(I)-(X)U complex as well as the (X)U-Hg(II)-(X)U complex were formed. ESI-TOF MS analysis also indicated formation of the metal ion-DNA complexes.

The 2',5'-oligoadenylate (2-5A) system is an interferon (IFN)-regulated RNA decay pathway that provides innate immunity against viral infections. The biological action of the 2-5A system is mediated by RNase L, an endoribonuclease that becomes enzymatically active after binding to 2-5A. It has been reported that the 5'-phosphoryl group of 2-5A is required for RNase L activation. However, we have found that 5'-O-dephosphorylated 2-5A tetramer analogs with 8-methyladenosine at the 2'-terminus were more effective as an activator of RNase L than the parent 2-5A (p5'A2'p5'A2'p5'A2'p5'A2'). Introduction of 8-methyladenosine is thought to induce a dramatic shift in the binding site of RNase L.

We describe herein the results of (i) enzymatic recognition for imidazopyridopyrimidine (Im):naphthyridine (Na) base pairs and (ii) further primer extension reactions after the Im:Na base pairs by DNA polymerases. Among the base pairs examined, ImN(O):NaO(N) base pair was rather selectively recognized by Klenow fragment exo(-) [F(exo(-))]as complementary base. However, this DNA polymerase did not catalyze primer extension reactions after the ImN(O):NaO(N) base pair. Therefore, we carried out a screening of DNA polymerases to promote the primer extension reaction as well as to improve the selectivity of base pair recognition. As a result, a family B DNA polymerase, especially Deep Vent (exo(-)), seemed most promising for this purpose.

We synthesized multiple pyrene-modified RNA sequences having two kinds of consecutive sequences, U(Py)U(Py) and A(Py)A(Py), and investigated their duplex formations and the pyrene associations.

To refine zinc-finger nuclease (ZFN) technology, we constructed a sandwiched ZFN, in which a DNA cleavage enzyme was sandwiched with two artificial zinc-finger proteins (AZPs). Because the sandwiched ZFN is designed to cleave the DNA between the two AZP-binding sites, the sandwiched ZFN is expected to bind preferentially to a DNA substrate rather than to cleavage products and thereby cleave it with multiple turnovers. To prove the concept, we sandwiched a staphylococcal nuclease (SNase), which cleaves DNA as a monomer, between two 3-finger AZPs. The AZP-sandwiched SNase cleaved large amounts of dsDNA site-specifically. Such multiple-turnover cleavage was not observed with control nucleases that possess a single AZP.