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11.
Li Q Sankaranarayanan J Hawk M Tran VT Brown JL Gudmundsdottir AD 《Photochemical & photobiological sciences》2012,11(4):744-751
The irradiation of ester 1 in methanol and chloroform does not yield any photoproducts, whereas the photolysis of 1 in dry argon-saturated benzene produces cyclobutanol 4, which is converted to lactone 5 by the addition of HCl. Laser-flash photolysis of ester 1 demonstrates that 1 undergoes intramolecular H-atom abstraction to form the biradical 2 (λ(max)~ 310 nm, τ = 200 ns, benzene), which intersystem crosses to photoenols, Z-3 (λ(max)~ 380 nm, τ = 30-60 μs, benzene) and E-3 (λ(max)~ 380 nm, τ = 11 ms, benzene). Density functional theory calculations were performed to support the proposed mechanism for forming cyclobutanol 4 and to explain how steric demand facilitates photoenol E-3 to form cyclobutanol 4 rather than lactone 5. 相似文献
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Although microsatellite mutation rates generally increase with increasing length of the repeat tract, interruptions in a microsatellite may stabilize it. We have performed a direct analysis of the effect of microsatellite interruptions on mutation rate and spectrum in cultured mammalian cells. Two mononucleotide sequences (G17 and A17) and a dinucleotide [(CA)17] were compared with interrupted repeats of the same size and with sequences of 8 repeat units. MMR-deficient (MMR−) cells were used for these studies to eliminate effects of this repair process. Mutation rates were determined by fluctuation analysis on cells containing a microsatellite sequence at the 5′ end of an antibiotic-resistance gene; the vector carrying this sequence was integrated in the genome of the cells. In general, interrupted sequences had lower mutation rates than perfect ones of the same size, but the magnitude of the difference was dependent upon the sequence of the interrupting base(s). Some interrupted repeats had mutation rates that were lower than those of perfect sequences of the same length but similar to those of half the length. This suggests that interrupting bases effectively divide microsatellites into smaller repeat runs with mutational characteristics different from those of the corresponding full-length microsatellite. We conclude that interruptions decrease microsatellite mutation rate and influence the spectrum of frameshift mutations. The sequence of the interrupting base(s) determines the magnitude of the effect on mutation rate. 相似文献
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The aim of this study was to determine the first effect of lead on microbial activity in soil. The study was carried out in the soil samples from four different radish (Raphanus sativus L. var. radicula, Brassicaceae) fields along the highway in a district (Kadirli, Osmaniye) of the Eastern Mediterranean Region, Turkey. After the calculation of Pb contents, the Pb amounts of the soil samples were brought up to 50 and 100 mg Pb kg?1 by treatment with Pb(NO 3 ) 2 , and the samples for the carbon and the nitrogen mineralization were incubated under controlled conditions (28°C, constant moist). The carbon mineralization was determined by a CO 2 respiration method for 30 days. The nitrogen mineralization was observed in vitro for 6 weeks. The untreated group was statistically different from the 50 and 100 mg Pb kg?1 treatments in the aspect of the C(CO 2 ) outlet during mineralization (P ≤ 0.05), but difference between the 50 and 100 mg Pb kg?1 treatments was not significant. NH 4 -N and NO 3 -N contents of each soil were shown differences between across treatments. Based on these results, it is possible to conclude that the addition of 50 and 100 mg Pb kg?1 provided a toxic effect threshold for the microbial activity into 30 days. 相似文献
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Twelve fungi namelyAlternaria alternata, Aspergillus flavus, A niger, A ochraceus, Actinomucor repens, Capnodoium spp., Curvularia lunata, Fusarium
pallidoroseum, F solani, F verticillioides, Penicillium citrinum and Rhizopus stolonifer were recorded from samples ofAegle marmelos, Aesculus indica, Buchanania lanzan andPinus gerardiana. In case ofPrunus amygdalus only Rstolonifer was recorded. A significant variation in pattern of mycoflora incidence was observed in terms of source and season. Fungal
infestation in most of the substrates was found to be highest during monsoon. Aflatoxins were the most common mycotoxins elaborated
by different isolates ofA flavus obtained fromA marmelos, B lanzan andP gerardiana. The amount of aflatoxins produced by the toxigenic isolates ofA flavus was in the range of traces to 0.9–26.0 μg/ml inA marmelos, 0.8–17.5 μg/ml inP gerardiana and 0.65–13.2 μg/ml inB lanzan. The percentage toxigenicity was comparatively lower in the isolates of other mycotoxigenic fungi. Aflatoxins were detected
almost in all the samples analyzed for mycotoxin contamination. However, traces of zearalenone were detected inA marmelos. The concentration of aflatoxin B1 was in the range of 0.13–0.75 μg/g inA marmelos, 0.09–0.60 μg/g inP gerardiana and 0.01–0.20 ug/g inB lanzan. Mycotoxins were not detected inAesculus indica andPrunus amygdalus. 相似文献
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The tomato geneRSI-1 was previously identified as a molecular marker for auxin-induced lateral root initiation. We have further characterized
the expression mode of theRSI-1 gene in tomato andArabidopsis thaliana. Northern blot analyses revealed that the gene was induced specifically by auxin in tomato roots and hypocotyls. For experiments
with transgenic plants, the 5′ flanking region of theRSI-1 gene was linked to a GUS reporter gene, then transformed into tomato andArabidopsis. In these transgenic tomato plants, GUS activity was detected at the sites of initiation for lateral and adventitious roots.
Expression of the fusion gene was auxin-dependent and tissue-specific. This was consistent with results from the northern
blot analyses. In transgenicArabidopsis, the overall expression pattern of theRSI-GUS gene, including tissue specificity and auxin inducibility, was comparable to that in transgenic tomato seedlings. These results
indicate that an identical regulatory mechanism for lateral root initiation might be conserved in both plants. Thus, the expression
mode of theRSI-CUS gene inArabidopsis mutants defective in lateral root development should be investigated to provide details of this process. 相似文献