Nucleic acids symposium series最新文献

We investigated the relationship between electrophoretic behaviors and higher order structures of triplet repeat DNA fragments by means of capillary electrophoresis and atomic force microscopy (AFM). It was suggested that the mobility difference between triplet repeat DNA and random sequence DNA should be correlated to differences in their dynamic conformation.

The dynamic and static properties of the fluorescence of a pyrene-introduced oligonucleotide 16 mer and its hybrid with a target 32 mer. Their fluorescence quantum yields (< 1%) were much weaker than that of unsubstituted pyrene and their fluorescence lifetime of the major decay components were less than 1 ns. The rapid fluorescence quenching was due to the interaction between the fluorophore and bases in the oligonucleotides. The fluorescence of pyrene was quenched efficiently by TMP and slightly by AMP. The quenching by CMP and GMP were the intermediate case.

RecA-double stranded (ds) DNA complexes have been studied by atomic force microscopy (AFM). When the complexes were prepared in the presence of ATP gamma S, fully covered RecA-dsDNA filaments were observed by AFM. When the concentration of RecA proteins was lower, various lengths of filaments were found. The variation of the observed structures may directly reflect the real distribution of the intermediate complexes in the reaction mixture, as the mixture was simply deposited on a mica surface for AFM observation without special fixation or staining. The use of a carbon nanotube (CNT) AFM tip enabled high resolution to reveal the periodicity of RecA-dsDNA filaments. Our observations demonstrated the potential of the AFM method for the structural studies of the RecA-dsDNA complexes, especially their intermediate states.

Mechanism of DNA damage by the p-cyanobenzamide (pCyBz)-oligothiazole derivatives were investigated by HPLC analysis. The oxidation product of dG by the photocleaver was imidazolone (dIz).

In this study, we have investigated non-enzymatic oligomerization of an activated racemic mononucleotide in the presence of Na(+)-montmorillonite. Oligomers up to the decamer in length were formed by oligomerization reactions of activated D- and L-mononucleotides. Similarly, oligomerization of an activated racemic mononucleotide results in the formation of oligomers up to the octamer. These results suggest that montmorillonite catalysis is quite efficient for the oligomerization of racemic monomers, though it is somewhat less efficient than that of D- and L-monomers.

Homogeneous Ce(IV) complex of EDTA promptly hydrolyzes oligonucleotides under physiological conditions. Moreover, the activity of Ce(IV)/EDTA for DNA hydrolysis is promoted by the addition of amines. When [Ce(IV)/EDTA] = 5 mumol dm3 and [ethylenediamine] = 100 mmol dm3, the catalytic activity is about 50 times as large as that of Ce(IV)/EDTA. The combination of Ce(IV)/EDTA and amines is eminent tools for the future molecular biology and biotechnology.

We have previously shown that a positive regulator, HutP, of Bacillus subtilis hut operon is a RNA binding protein. Here, we report precise binding site of HutP in cis-regulatory region on hut mRNA and the role of HutP in histidine-dependent antitermination of hut expression. Ethylnitrosourea modification interference assay showed that four binding sites of HutP were found in the cis-regulatory sequences and were located at the stem and the internal loop of an antiterminator structure. In vitro transcription assay indicated that HutP suppressed transcription termination in the presence of histidine. These results suggest that HutP function as an antiterminator in response to the presence of histidine.

Tobacco BY2 cells were withered away by the physical contact with intestinal bacterium Escherichia coli. In contrast, plant pathogenic bacterium Agrobacterium tumefaciens with/without tumor inducing Ti plasmid was not so toxic as E. coli. Mini-cells of E. coli decreased their toxicity.

We investigated the molecular mechanisms of cell death induced by 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)cytosine (ECyd, TAS-106: Figure 1), a potent inhibitor of RNA synthesis, using mouse mammary tumor FM3A cells and human fibrosarcoma HT1080 cells. ECyd induced the characteristics of apoptosis on these cells, such as morphological changes, DNA fragmentations and caspase-3-like protease activation. General caspases inhibitor (Z-Asp-CH2-DCB) inhibited cell death. Interestingly, we also found that ECyd induced rRNA fragmentation with the size of 3.2, 2.8 and 1.5 kb, and which might be caused by inhibition of RNA synthesis. rRNA fragmentation was mainly occurred in D8 domain of 28 S rRNA, and the end of 5'-terminal sequence of 1.5 kb fragment was C3220pC3221p or C3221pG3222p, that was identical to the recognition sequence of RNase L. Furthermore, the fragmentation patterns of rRNA digested with RNase L resembled that of ECyd treated cells in shape. These results indicate that antitumor mechanisms of ECyd are involved in activation of RNase L. rRNA fragmentation may be one of the death events as a result of inhibition of RNA synthesis and play an important role in the antitumor activity of ECyd.

A benzoyl group was introduced onto the 3'-hydroxyl group of 6-chloropurine riboside by treatment with benzoic anhydride in the presence of a base in aqueous solution. The product (3b) was converted to 9-(2,3-Di-deoxy-2-fluoro-beta-D-threo-pentofuranosyl)adenine (1, FddA) in 6 steps, including radical deoxygenation.