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排序方式: 共有252条查询结果,搜索用时 15 毫秒
241.
We derive the boundary condition for a subdiffusive particle interacting with a reactive boundary with a finite reaction rate. Molecular crowding conditions, that are found to cause subdiffusion of larger molecules in biological cells, are shown to effect long-tailed distributions with an identical exponent for both the unbinding times from the boundary to the bulk and the rebinding times from the bulk. This causes a weak ergodicity breaking: typically, an individual particle either stays bound or remains in the bulk for very long times. We discuss why this may be beneficial for in vivo gene regulation by DNA-binding proteins, whose typical concentrations are nanomolar. 相似文献
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A validated HPLC-UV method was developed for the determination of R(-), S(+)-atenolol and R(-), S(+)-propranolol in pharmaceutical formulations. The proposed method required no elaborate sample preparation and was found to be selective, linear, and repeatable within the established ranges. Atenolol and propranolol isomers were separated using a Chirex 3022 (S) column with the mobile phases hexane-dichloromethane-methanol-trifluoroacetic acid (35 + 35 + 5 + 0.25, v/v/v/v) and hexane-dichloromethane-ethanol-trifluoroacetic acid (55 + 40 + 5 + 0.25, v/v/v/v), respectively. The LOD values of R(-) and S(+)-atenolol were 12.3 and 9.86 microg/mL, respectively, and 0.61 and 0.89 microg/mL, respectively, for R(-) and S(+)-propranolol. Retention times of R(-)-propranolol and S(+)-propranolol were 12.4 and 14.3 min, respectively, and 29.06 and 32.71 min, respectively, for (R)-atenolol and (S)-atenolol. The proposed method was applied to the determination of enantiomers in pharmaceutical formulations, and no interference from any excipients was found. 相似文献
245.
A.H. Bhrawy A.A. Alshaery E.M. Hilal Michelle Savescu Daniela Milovic Kaisar R. Khan Mohammad F. Mahmood Zlatko Jovanoski Anjan Biswas 《Optik》2014
This paper studies the propagation of solitons through birefringent fibers in the presence of spatio-temporal dispersion. Both Kerr and parabolic laws of nonlinearity are addressed. The exact 1-soliton solutions are obtained. There are several constraint conditions that ensure soliton solutions are derived. Three types of solitons are obtained: bright, dark and singular solitons. 相似文献
246.
This paper studies coupled nonlinear Schrödinger's equation (NLSE) that appears in a cascaded system. Both Kerr law and power law nonlinearities are considered. Bright and dark soliton solutions are retrieved for these nonlinearities. The corresponding constraint conditions naturally fall out that from the mathematical expressions that must remain valid for solitons to exist. 相似文献
247.
Nonlinear Dynamics - This paper treats comprehensively the construction of problems from nonlinear dynamics and constrained optimization amenable to parameter continuation techniques and with... 相似文献
248.
One‐Pot Semisynthesis of Exon 1 of the Huntingtin Protein: New Tools for Elucidating the Role of Posttranslational Modifications in the Pathogenesis of Huntington’s Disease
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Annalisa Ansaloni Dr. Zhe‐Ming Wang Dr. Jae Sun Jeong Francesco Simone Ruggeri Prof. Dr. Giovanni Dietler Prof. Dr. Hilal A. Lashuel 《Angewandte Chemie (International ed. in English)》2014,53(7):1928-1933
The natural enzymes involved in regulating many of the posttranslational modifications (PTMs) within the first 17 residues (Nt17) of Huntingtin exon 1 (Httex1) remain unknown. A semisynthetic strategy that allows the site‐specific introduction of PTMs within Nt17 by using expressed protein ligation (EPL) was developed. This strategy was used to produce untagged wild‐type (wt) and T3‐phosphorylated (pT3) Httex1 containing 23 glutamine residues (Httex1‐23Q). Our studies show that pT3 significantly slows the oligomerization and fibrillization of Httex1‐23Q and that Httex1 variants containing polyQ repeats below the pathogenic threshold readily aggregate and form fibrils in vitro. These findings suggest that crossing the polyQ pathogenic threshold is not essential for Httex1 aggregation. The ability to produce wt or site‐specifically modified tag‐free Httex1 should facilitate determining its structure and the role of N‐terminal PTMs in regulating the functions of Htt in health and disease. 相似文献
249.
Hilal M Rodríguez-Montelongo L Rosa M Gallardo M González JA Interdonato R Rapisarda VA Prado FE 《Photochemistry and photobiology》2008,84(6):1480-1486
Effects of solar and supplemental UV-B radiation on UV-B-absorbing compounds and malondialdehyde (MDA) accumulations in the peel of lemons collected in summer and winter were analyzed. UV-B-absorbing compounds were higher in flavedo than in albedo tissue in both seasons; however, the highest values were observed in summer. These compounds were also higher in outer than in inner flavedo surface. Lemons were categorized as sun-, semisun- and shaded-lemon according to localization inside the tree canopy. Depending on-tree localization UV-B-absorbing compounds were higher in flavedo of sun-lemon than in semisun- and shaded-lemon. Supplementary UV-B radiation (22 kJ m(-2) day(-1) UV-BBE) induced UV-B-absorbing compound synthesis in on-tree and postharvest lemons. Two minutes of supplemental UV-B irradiation in summer lemons produced a strong increment (300%) of UV-B-absorbing compound content, whereas in winter lemons a slight increase (30%) was observed only after 3 min of irradiation. By contrast, UV-B-absorbing compound accumulation was not observed in albedo. MDA accumulation showed approximately a similar trend of UV-B-absorbing compounds. According to our results, solar UV-B was not required for UV-B-absorbing compound accumulation in lemon peel. Relationships between UV-B-absorbing compounds, MDA, reactive oxygen species and pathogen protection are also discussed. 相似文献
250.
Polarographic anodic oxidation wave that can be correlated to total antioxidant capacity (TAC) in Human serum corresponds to 2H+ and 2e process. The limiting current of the wave, which is proportional to TAC, is strongly influenced by UV light intensity and irradiation time. A mechanism has been proposed to explain the effects of UV on anodic wave related to antioxidant behavior. Results show that decomposition processes follow to the excitation a transitory product at three different light intensities at 340 nm. The number of decomposition products increase with increasing light intensity. The rate of oxygen radical capture ability of the serum antioxidants might be estimated by comparing the changes of anodic wave in the absence and presence of naturally dissolved oxygen. 相似文献