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41.
David TR Coulson Simon Brockbank Joseph G Quinn Suzanne Murphy Rivka Ravid G Brent Irvine Janet A Johnston 《BMC molecular biology》2008,9(1):1-11
Background
Transfection of cells with gene-specific, single-stranded oligonucleotides can induce the targeted exchange of one or two nucleotides in the targeted gene. To characterize the features of the DNA-repair mechanisms involved, we examined the maximal distance for the simultaneous exchange of two nucleotides by a single-stranded oligonucleotide. The chosen experimental system was the correction of a hprt-point mutation in a hamster cell line, the generation of an additional nucleotide exchange at a variable distance from the first exchange position and the investigation of the rate of simultaneous nucleotide exchanges.Results
The smaller the distance between the two exchange positions, the higher was the probability of a simultaneous exchange. The detected simultaneous nucleotide exchanges were found to cluster in a region of about fourteen nucleotides upstream and downstream from the first exchange position.Conclusion
We suggest that the mechanism involved in the repair of the targeted DNA strand utilizes only a short sequence of the single-stranded oligonucleotide, which may be physically incorporated into the DNA or be used as a matrix for a repair process. 相似文献42.
Ligand rebinding: self-consistent mean-field theory and numerical simulations applied to surface plasmon resonance studies 总被引:1,自引:0,他引:1
Gopalakrishnan M Forsten-Williams K Cassino TR Padro L Ryan TE Täuber UC 《European biophysics journal : EBJ》2005,34(7):943-958
Rebinding of dissociated ligands from cell surface proteins can confound quantitative measurements of dissociation rates important for characterizing the affinity of binding interactions. This can be true also for in vitro techniques such as surface plasmon resonance (SPR). We present experimental results using SPR for the interaction of insulin-like growth factor-I (IGF-I) with one of its binding proteins, IGF binding protein-3 (IGFBP-3), and show that the dissociation, even with the addition of soluble heparin in the dissociation phase, does not exhibit the expected exponential decay characteristic of a 1:1 binding reaction. We thus consider the effect of (multiple) rebinding events and, within a self-consistent mean-field approximation, we derive the complete mathematical form for the fraction of bound ligands as a function of time. We show that, except for very low association rate and surface coverage, this function is nonexponential at all times, indicating that multiple rebinding events strongly influence dissociation even at early times. We compare the mean-field results with numerical simulations and find good agreement, although deviations are measurable in certain cases. Our analysis of the IGF-I–IGFBP-3 data indicates that rebinding is prominent for this system and that the theoretical predictions fit the experimental data well. Our results provide a means for analyzing SPR biosensor data where rebinding is problematic and a methodology to do so is presented. 相似文献
43.
Depending on geographical location, plants are exposed to variable amounts of UVB radiation and herbivore attack. Because the role(s) of UVB in the priming and/or accumulation of plant defence metabolites against herbivores are not well understood, we used field‐grown Nicotiana attenuata plants to explore the effects of UVB on herbivore performance. Consistent with previous reports, UVB‐exposed plants accumulated higher levels of ultraviolet (UV)‐absorbing compounds (rutin, chlorogenic acid, crypto‐chlorogenic acid and dicaffeoylspermidine). Furthermore, UVB increased the accumulation of jasmonic acid, jasmonoyl‐L‐isoleucine and abscisic acid, all phytohormones which regulate plant defence against biotic and abiotic stress. In herbivore bioassays, N. attenuata plants experimentally protected from UVB were more infested by mirids in three consecutive field seasons. Among defence metabolites measured, 17‐hydroxygeranyllinalool diterpene glycosides (HGL‐DTGs) showed strongly altered accumulation patterns. While constitutive HGL‐DTGs levels were higher under UVB, N. attenuata plants exposed to mirid bugs (Tupiocoris notatus) had still more HGL‐DTGs under UVB, and mirids preferred to feed on HGL‐DTGs‐silenced plants when other UVB protecting factors were eliminated by UVB filters. We conclude that UVB exposure not only stimulates UV protective screens but also affects plant defence mechanisms, such as HGL‐DTGs accumulation, and modulates ecological interactions of N. attenuata with its herbivores in nature. 相似文献
44.
Arakkaveettil Kabeer Farha Thasneem TR Aswathy Purushothaman Jaseetha Abdul Salam Abdulla Mohamed Hatha 《Journal of Genetic Engineering and Biotechnology》2018,16(2):253-258
Marine environments are substantially untapped source for the isolation of bacteria with the capacity to produce various extracellular hydrolytic enzymes, which have important ecological roles and promising biotechnological applications. Hydrolases constitute a class of enzymes widely distributed in nature from bacteria to higher eukaryotes. Marine microbial communities are highly diverse and have evolved during extended evolutionary processes of physiological adaptations under the influence of a variety of ecological conditions and selection pressures. A number of marine hydrolases have been described, including amylases, lipases and proteases, which are being used extensively for biotechnological applications. The present study was carried out to isolate marine bacteria from continental slope sediments of the eastern Arabian Sea and explore their biotechnological potential. Among the 119 isolates screened, producers of amylases (15%), caseinases (40%), cellulases (40%), gelatinases (60%), lipases (26%), ligninases (33%), phytase (11%) and Malachite Green dye degraders (16%) were detected. Phylogenetic analysis based on 16S rRNA gene sequencing showed that predominant marine sediment bacteria possessing more than four enzymatic activities belonged to the phyla Firmicutes and Proteobacteria, was assigned to the genera Bacillus, Planococcus, Staphylococcus, Chryseomicrobium, Exiguobacterium and Halomonas. Biodegradation of the dye Malachite Green using the liquid decolorization assay showed that both the individual cultures (Bacillus vietnamensis, Planococcus maritimus and Bacillus pumilus) and their consortium were able to decolorize more than 70% of dye within 24?h of incubation. This is the first report on diversity and extracellular hydrolytic enzymatic activities and bioremediation properties of bacteria from continental slope sediment of eastern Arabian Sea. 相似文献
45.
A simple equipment was developed to cultivate young cereal plants under enhanced CO2 concentration. Cultivation system permits growing of about 40 barley seedlings for about 2 to 3 weeks. The system consists
of two identical growth chambers (volume about 30 dm3), gas conditioning circuit and measuring circuit with an infra-red CO2 analyser. Capabilities of the whole equipment were tested by growing barley plants under 330 and 1000 cm3 (CO2)m−3 and in combination with high or low nitrate level. 相似文献
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47.
Since it has been demonstrated that chronic administration of reserpine to rats produces CF-like alterations, we have studied the lung resistance to bacterial infections in animals treated with reserpine. Mice of the BALB/c inbred strain were injected subcutaneously with different doses of reserpine for 7 days; after, they were submitted to an infective aerosol containing in a nebulization chamber. With each pair of exposed animals, an individual value of the uncleared bacteria ratio (UBR) at 4 hours was obtained. Reserpinized animals showed a significant increase in UBR values when compared to control mice (p < 0.05 and p < 0.01 depending on the doses), suggesting an impairment of the lung antibacterial defenses. Although pharmacological doses of reserpine produce catecholamine depletion, we can not conclude that this action upon the nervous system is the only cause of the CF-like response we detected. In conclusion, the observed UBR decrease lends support to the concept of a reserpine-induced CF animal model. 相似文献