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排序方式: 共有245条查询结果,搜索用时 31 毫秒
41.
Laura J. Marinelli Mariana Piuri Zuzana Swigoňová Amrita Balachandran Lauren M. Oldfield Julia C. van Kessel Graham F. Hatfull 《PloS one》2008,3(12)
Advances in DNA sequencing technology have facilitated the determination of hundreds of complete genome sequences both for bacteria and their bacteriophages. Some of these bacteria have well-developed and facile genetic systems for constructing mutants to determine gene function, and recombineering is a particularly effective tool. However, generally applicable methods for constructing defined mutants of bacteriophages are poorly developed, in part because of the inability to use selectable markers such as drug resistance genes during viral lytic growth. Here we describe a method for simple and effective directed mutagenesis of bacteriophage genomes using Bacteriophage Recombineering of Electroporated DNA (BRED), in which a highly efficient recombineering system is utilized directly on electroporated phage DNA; no selection is required and mutants can be readily detected by PCR. We describe the use of BRED to construct unmarked gene deletions, in-frame internal deletions, base substitutions, precise gene replacements, and the addition of gene tags. 相似文献
42.
Sucosky P Padala M Elhammali A Balachandran K Jo H Yoganathan AP 《Journal of biomechanical engineering》2008,130(3):035001
Mechanical forces are known to affect the biomechanical properties of native and engineered cardiovascular tissue. In particular, shear stress that results from the relative motion of heart valve leaflets with respect to the blood flow is one important component of their mechanical environment in vivo. Although different types of bioreactors have been designed to subject cells to shear stress, devices to expose biological tissue are few. In an effort to address this issue, the aim of this study was to design an ex vivo tissue culture system to characterize the biological response of heart valve leaflets subjected to a well-defined steady or time-varying shear stress environment. The novel apparatus was designed based on a cone-and-plate viscometer. The device characteristics were defined to limit the secondary flow effects inherent to this particular geometry. The determination of the operating conditions producing the desired shear stress profile was streamlined using a computational fluid dynamic (CFD) model validated with laser Doppler velocimetry. The novel ex vivo tissue culture system was validated in terms of its capability to reproduce a desired cone rotation and to maintain sterile conditions. The CFD results demonstrated that a cone angle of 0.5 deg, a cone radius of 40 mm, and a gap of 0.2 mm between the cone apex and the plate could limit radial secondary flow effects. The novel cone-and-plate permits to expose nine tissue specimens to an identical shear stress waveform. The whole setup is capable of accommodating four cone-and-plate systems, thus concomitantly subjecting 36 tissue samples to desired shear stress condition. The innovative design enables the tissue specimens to be flush mounted in the plate in order to limit flow perturbations caused by the tissue thickness. The device is capable of producing shear stress rates of up to 650 dyn cm(-2) s(-1) (i.e., maximum shear stress rate experienced by the ventricular surface of an aortic valve leaflet) and was shown to maintain tissue under sterile conditions for 120 h. The novel ex vivo tissue culture system constitutes a valuable tool toward elucidating heart valve mechanobiology. Ultimately, this knowledge will permit the production of functional tissue engineered heart valves, and a better understanding of heart valve biology and disease progression. 相似文献
43.
U Subrahmanyeswara Rao Randy E Steimle Premalatha Balachandran 《The Journal of biological chemistry》2002,277(7):4900-4905
The amiloride-sensitive epithelial sodium channels (ENaC) mediate Na(+) reabsorption in epithelial tissues including distal nephron, colon, lung, and secretory glands and plays a critical role in pathophysiology of hypertension and cystic fibrosis. The ENaC is a multimeric protein composed of alpha-ENaC, beta-ENaC, and gamma-ENaC subunits. To study the biochemical properties of the channel, the subunit cDNAs of rat colon ENaC (rENaC) were subcloned into baculoviruses, and the corresponding proteins were expressed in Sf9 insect cells. The functional characteristics of the expressed rENaC were studied in planar lipid bilayers. The results show that expression of alpha-rENaC and alphabetagamma-rENaC in Sf9 insect cells results in the generation of cation-selective large conductance channels. Although the large conductance channels observed in the alpha-rENaC-containing membranes were unaffected by amiloride, the large conductance channels found in alphabetagamma-rENaC complex-containing membranes exhibited voltage-dependent flickering in the presence of micromolar amiloride. Possible implications of these observations are discussed. 相似文献
44.
K. Parthasarathy C. Praveen C. Balachandran P. Senthil kumar S. Ignacimuthu P.T. Perumal 《Bioorganic & medicinal chemistry letters》2013,23(9):2708-2713
Cu(OTf)2 catalyzed efficient synthesis of spiropyrano[3,2-b]pyran-4(8H)-ones is accomplished via one-pot three component reaction between isatin, kojic acid and active methylenes. This synthetic protocol is operationally simple and affords product with good to excellent yields at a short reaction time. The synthesized compounds were evaluated for their tumor cell growth inhibitory activity against the human lung cancer cell line (A549) and found that 13 compounds exhibited moderate to good anticancer potency. Molecular docking studies were performed for all the synthesized compounds and the results showed that compound 4e showed greater affinity for anaplastic lymphoma kinase (ALK) receptor. 相似文献
45.
M. Srinivasa Rao M. Chellapandian M. R. V. Krishnan 《Bioprocess and biosystems engineering》1995,13(4):211-214
Urease was immobilized onto gelatin-poly (HEMA) copolymer by covalent linkage. Maximum amount of urease was immobilized onto the support at a pH of 8.5. The optimal pH of the immobilized urease was similar to that of free urease; the optimal temperature showed an increase of 10 °C over the free enzyme. The stability of the immobilized urease for a range of pH, temperature and shelf life was greater than the corresponding values for the free enzyme. The same result was obtained for k
m
also.Grateful acknowledgement is made to CSIR, Govt. of India for the research associateship conferred on Dr. M. Chellapandian which helped the progress of this piece of research investigation. 相似文献
46.
S. George M. Chellapandian B. Sivasankar K. Jayaraman 《Bioprocess and biosystems engineering》1997,16(2):83-85
A method is reported for the treatment of industrial fertilizer effluent rich in urea by a new coupling method to immobilize crude urease onto polyester which is having high flow through property in columns. Kinetics of the immobilized enzyme is established in small column. A typical treatment process with two larger columns in packed bed mode is discussed with and without recycling the treated effluent. 相似文献
47.
High altitude flights by ruddy shelduck Tadorna ferruginea during trans‐Himalayan migrations 下载免费PDF全文
N. Parr S. Bearhop D. C. Douglas J. Y. Takekawa D. J. Prosser S. H. Newman W. M. Perry S. Balachandran M. J. Witt Y. Hou Z. Luo L. A. Hawkes 《Journal of avian biology》2017,48(10):1310-1315
Birds that migrate across high altitude mountain ranges are faced with the challenge of maintaining vigorous exercise in environments with limited oxygen. Ruddy shelducks are known to use wintering grounds south of the Tibetan Plateau at sea level and breeding grounds north of Himalayan mountain range. Therefore, it is likely these shelducks are preforming high altitude migrations. In this study we analyse satellite telemetry data collected from 15 ruddy shelduck from two populations wintering south of the Tibetan Plateau from 2007 to 2011. During north and south migrations ruddy shelduck travelled 1481 km (range 548–2671 km) and 1238 km (range 548–2689 km) respectively. We find mean maximum altitudes of birds in flight reached 5590 m (range of means 4755–6800 m) and mean maximum climb rates of 0.45 m s–1 (range 0.23–0.74 m s–1). The ruddy shelduck is therefore an extreme high altitude migrant that has likely evolved a range of physiological adaptations in order to complete their migrations. 相似文献
48.
Microsatellites are abundant across prokaryotic and eukaryotic genomes. However, comparative analysis of microsatellites in the organellar genomes of plants and their utility in understanding phylogeny has not been reported. The purpose of this study was to understand the organization of microsatellites in the coding and non-coding regions of organellar genomes of major cereals viz., rice, wheat, maize and sorghum. About 5.8-14.3% of mitochondrial and 30.5-43.2% of chloroplast microsatellites were observed in the coding regions. About 83.8-86.8% of known mitochondrial genes had at least one microsatellite while this value ranged from 78.6-82.9% among the chloroplast genomes. Dinucleotide repeats were the most abundant in the coding and non-coding regions of the mitochondrial genome while mononucleotides were predominant in chloroplast genomes. Maize harbored more repeats in the mitochondrial genome, which could be due to the larger size of genome. A phylogenetic analysis based on mitochondrial and chloroplast genomic microsatellites revealed that rice and sorghum were closer to each other, while wheat was the farthest and this corroborated with the earlier reported phylogenies based on nuclear genome co-linearity and chloroplast gene-based analysis. 相似文献
49.
Vijayalakshmi R Kanthimathi M Parthasarathi R Nair BU 《Bioorganic & medicinal chemistry》2006,14(10):3300-3306
Since conformation of the molecule plays a vital role in the activity of drug, we have investigated the DNA interaction of a chromium(III) complex with ligands in two conformations. Chromium(III) complexes derived from chiral binaphthyl Schiff base ligands, viz. R- and S-2,2'-bis(salicylideneamino) 1,1'-binaphthyl, have been synthesized and characterized by mass, IR, and electronic spectra. The interaction of these R- and S-binaphthyl Schiff base chromium(III) complexes with CT-DNA was investigated with the goal of examining whether the chirality has an influence on the chromium(III)-DNA binding properties. The difference in chirality of the ligand did not show any striking difference in binding properties. The binding constants for R and S conformers were estimated to be 18 (+/-0.4) x 10(3) and 9.4 (+/-0.3) x 10(3) M(-1), respectively, through spectroscopic titrations. All the experimental results are suggestive that both the isomers are DNA groove binders. The results of steady-state as well as time-resolved fluorescence experiments, however, suggest that the R conformer has restricted mobility when bound to DNA because it is more deeply buried in the groove of DNA compared to the S isomer. 相似文献
50.