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11.
Matsuda S Henry AA Schultz PG Romesberg FE 《Journal of the American Chemical Society》2003,125(20):6134-6139
The stability and replication of DNA containing self-pairs formed between unnatural nucleotides bearing benzofuran, benzothiophene, indole, and benzotriazole nucleobases are reported. These nucleobase analogues are based on a similar scaffold but have different hydrogen-bond donor/acceptor groups that are expected to be oriented in the duplex minor groove. The unnatural base pairs do not appear to induce major structural distortions and are accommodated within the constraints of a B-form duplex. The differences between these unnatural base pairs are manifest only in the polymerase-mediated extension step, not in base-pair stability or synthesis. The benzotriazole self-pair is extended with an efficiency that is only 200-fold less than a correct natural base pair. The data are discussed in terms of available polymerase crystal structures and imply that further modifications may result in unnatural base pairs that can be both efficiently synthesized and extended, resulting in an expanded genetic alphabet. 相似文献
12.
Yasuo Saegusa Sakayu Iida Shigeo Nakamura Nguyen Chau Yoshio Iwakura 《Journal of polymer science. Part A, Polymer chemistry》1984,22(5):1017-1023
Aromatic polythioamide-oxothioxoquinazolines were synthesized by the polycondensation of 2,2′-(m-phenylene)bis-1,3,4-thiadiazoline-5-thione with aromatic bis-o-amino esters. The polymerizations were carried out at 160°C in acidic media such as m-cresol, sulfolane, and polyphosphoric acid to produce polymers with reduced viscosities up to 0.5 dL/g. These polymers were soluble in polar aprotic solvents like N-methyl-2-pyrrolidone and some acidic media including m-cresol. The polythioamide-oxothioxoquinazolines showed relatively good thermal stability with 10% weight loss at 344–394°C in air. 相似文献
13.
14.
We calculated the (dµ)
n=1 +t scattering in the energy region of the (dtµ)* resonant states below then=2 level of the tµ atom. From the cross sections, we estimated the resonant energies, widths and branching ratios. We found eleven resonant states with angular momentumJ=0, and some of their resonant energies relative to then=2 level of tµ are small enough to form the [(dtµ)* dee] by the Vesman mechanism. These resonant states decay to (dµ)[inn=1 +t or (tµ)
n=1 + d scattering states. The total decay rates are about 1011 s–1 which is three orders of magnitude larger than the fusion rates of (dtµ)*4 He + n+ 17.6 MeV + µ. The main part of the decaying channel from the shallow resonant states is the (dµ)
n=1 +t channel. The branching ratios of the (dµ)
n=1 +t decay channel are around 0.9. Most of the muons that reach to then=2 states of tµ can transfer to then=1 state of du through (tµ)
n=2 + D2 [(dtµ)*dee] and (dtµ)* (dµ)
n=1 +t processes. 相似文献
15.
Using the coupled rearrangement channel method, we have calculated resonance energies for meta-stable states of the molecular ion dtµ* associated with the adiabatic 3 potential. The vacuum polarization effect was taken into account by direct inclusion of the Uehling potential in our three-body Hamiltonian. Comparing with the solution of the pure Coulombic Schrödinger equation a shift of approximately +0.1 eV is found. Thus the infinite series of states of the Coulombic Schrödinger equation becomes truncated. Eleven states remain semi-bound, five of them with binding energy smaller than the dissociation energy of the D2 molecule, facilitating formation of dtµ* in tµ(2s)-D2 scattering by means of the Vesman-mechanism. 相似文献
16.
The simultaneous ultramicrodetermination of heterogeneous halogens in organic compounds was carried out by the potentiometric titration with 0.002 M silver nitrate after the sample was decomposed by the flask combustion method. In examination of the titration, it was found that clear potential break at the end point was obtained by controlling the delivery speed of the titrant at 0.2 ml/min or slower and the temperature of the solution to be titrated at ca. 10 °C when chloride ion is present. The error due to coprecipitation during the titration and the effect of the mole ratio of heterogeneous halide ions in the sample solution was examined and discussed. The analysis of organic halogen compounds resulted in an error of within 0.4% and standard deviation of less than 0.25%. 相似文献
17.
Reaction of 5-formyl-1,3-dimethyluracil with some active methylene compounds in the presence of base causes novel ring transformations to give the p-hydroxybenzoates and the nicotinate. 相似文献
18.
A new pulse sequence is proposed for the determination of scalar coupling correlation in small- and medium-sized organic compounds. The method uses a combination of the double pulsed field gradient spin-echo (DPFGSE) and the selective population transfer (SPT) techniques and is shown to be useful in the analysis of complex spectra with many overlapped signals. The usefulness of this method in the structural elucidation of natural substances is demonstrated using strychnine and digitoxin as examples. 相似文献
19.
A variety of O-alkylperoxycarbonic acids () were conveniently prepared by utilizing alkyloxycarbonylimidazoles () as their precursors. Epoxidation of alkenes with such peroxy-acids was studied and their reactivities were compared with those of peroxycarboxylic acids. 相似文献
20.
Shigeo Tazuke Kiyoo Shimada Seizo Okamura 《Journal of polymer science. Part A, Polymer chemistry》1969,7(3):879-888
The radical polymerizability of vinylpyridines in the presence of cobaltous chloride was studied in DMF solution, and the results were correlated with the spectroscopic data obtained for methanol solution. In general, the behavior of vinylpyridine complexed with cobaltous chloride is qualitatively the same as that of zinc complexes reported previously. The rates of polymerization were enhanced by the addition of cobaltous chloride when 4-vinylpyridine(4-VP) or 2-methyl-5-vinylpyridine(MVP) was the monomer, whereas the polymerization of 2-vinylpyridine(2-VP) was retarded by cobaltous chloride. The monomer reactivity of all the vinylpyridines was also enhanced by complex formation as studied by copolymerization with styrene. The enhancement of reactivity of 4-VP complexed with cobaltous chloride is somewhat smaller than that of the corresponding zinc complex. 相似文献