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71.
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73.
Bones from different portions of human skeleton are polished and cut to suitable sizes and then subjected to micro-indentation at various loads using Vicker's diamond pyramidal indenter. The Vicker's hardness number is found to differ slightly from portion to portion of the skeleton. Interferometric studies of the indentation reveal that the applied stress of indentation causes a 'pile-up' of material near the corners of the pyramidal indents. 相似文献
74.
P. Plocinski N. Arora K. Sarva E. Blaszczyk H. Qin N. Das R. Plocinska M. Ziolkiewicz J. Dziadek M. Kiran P. Gorla T. A. Cross M. Madiraju M. Rajagopalan 《Journal of bacteriology》2012,194(23):6398-6409
Bacterial cell division and cell wall synthesis are highly coordinated processes involving multiple proteins. Here, we show that Rv0008c, a novel small membrane protein from Mycobacterium tuberculosis, localizes to the poles and on membranes and shows an overall punctate localization throughout the cell. Furthermore, Rv0008c interacts with two proteins, CrgA and Wag31, implicated in peptidoglycan (PG) synthesis in mycobacteria. Deletion of the Rv0008c homolog in M. smegmatis, MSMEG_0023, caused bulged cell poles, formation of rounded cells, and defects in polar localization of Wag31 and cell wall synthesis, with cell wall synthesis measured by the incorporation of the [14C]N-acetylglucosamine cell wall precursor. The M. smegmatis MSMEG_0023 crgA double mutant strain showed severe defects in growth, viability, cell wall synthesis, cell shape, and the localization of the FtsZ, FtsI, and Wag31 proteins. The double mutant strain also exhibited increased autolytic activity in the presence of detergents. Because CrgA and Wag31 proteins interact with FtsI individually, we believe that regulated cell wall synthesis and cell shape maintenance require the concerted actions of the CrgA, Rv0008c, FtsI, and Wag31 proteins. We propose that, together, CrgA and Rv0008c, renamed CwsA for cell wall synthesis and cell shape protein A, play crucial roles in septal and polar PG synthesis and help coordinate these processes with the FtsZ-ring assembly in mycobacteria. 相似文献
75.
Kamal A Murty JN Viswanath A Sujitha P Ganesh Kumar C 《Bioorganic & medicinal chemistry letters》2012,22(14):4891-4895
In this letter, we describe the first synthesis of two recently isolated flavones 5-carbomethoxymethyl-7-hydroxy-2-pentylchromone (3a), 5-carboethoxymethyl-4',7-dihydroxyflavone (3b) and their derivatives (3c-t), evaluated for their antimicrobial, antioxidant and anticancer activities. Most of the synthesized compounds exhibited antimicrobial activity against the tested microbial strains and some of these compounds were found to be more potent as compared to the standard drugs like neomycin and luteolin. Interestingly, some of these synthesized compounds also showed moderate antioxidant property. 相似文献
76.
Madiraju MV Moomey M Neuenschwander PF Muniruzzaman S Yamamoto K Grimwade JE Rajagopalan M 《Molecular microbiology》2006,59(6):1876-1890
Oligomerization of the initiator protein, DnaA, on the origin of replication (oriC) is crucial for initiation of DNA replication. Studies in Escherichia coli (Gram-negative) have revealed that binding of DnaA to ATP, but not hydrolysis of ATP, is sufficient to promote DnaA binding, oligomerization and DNA strand separation. To begin understanding the initial events involved in the initiation of DNA replication in Mycobacterium tuberculosis (Gram-positive), we investigated interactions of M. tuberculosis DnaA (DnaA(TB)) with oriC using surface plasmon resonance in the presence of ATP and ADP. We provide evidence that, in contrast to what is observed in E. coli, ATPase activity of DnaA(TB) promoted rapid oligomerization on oriC. In support, we found that a recombinant mutant DnaA(TB) proficient in binding to ATP, but deficient in ATPase activity, did not oligomerize as rapidly. The corresponding mutation in the dnaA gene of M. tuberculosis resulted in non-viability, presumably due to a defect in oriC-DnaA interactions. Dimethy sulphate (DMS) footprinting experiments revealed that DnaA(TB) bound to DnaA boxes similarly with ATP or ADP. DnaA(TB) binding to individual DnaA boxes revealed that rapid oligomerization on oriC is triggered only after the initial interaction of DnaA with individual DnaA boxes. We propose that ATPase activity enables the DnaA protomers on oriC to rapidly form oligomeric complexes competent for replication initiation. 相似文献
77.
Chauhan A Lofton H Maloney E Moore J Fol M Madiraju MV Rajagopalan M 《Molecular microbiology》2006,62(1):132-147
The genetic factors responsible for the regulation of cell division in Mycobacterium tuberculosis are largely unknown. We showed that exposure of M. tuberculosis to DNA damaging agents, or to cephalexin, or growth of M. tuberculosis in macrophages increased cell length and sharply elevated the expression of Rv2719c, a LexA-controlled gene. Overexpression of Rv2719c in the absence of DNA damage or of antibiotic treatment also led to filamentation and reduction in viability both in broth and in macrophages indicating a correlation between Rv2719c levels and cell division. Overproduction of Rv2719c compromised midcell localization of FtsZ rings, but had no effect on the intracellular levels of FtsZ. In vitro, the Rv2719c protein did not interfere with the GTP-dependent polymerization activity of FtsZ indicating that the effects of Rv2719c on Z-ring assembly are indirect. Rv2719c protein exhibited mycobacterial murein hydrolase activity that was localized to the N-terminal 110 amino acids. Visualization of nascent peptidoglycan (PG) synthesis zones by probing with fluoresceinated vancomycin (Van-FL) and localization of green fluorescent protein-Rv2719c fusion suggested that the Rv2719c activity is targeted to potential PG synthesis zones. We propose that Rv2719c is a potential regulator of M. tuberculosis cell division and that its levels, and possibly activities, are modulated under a variety of growth conditions including growth in vivo and during DNA damage, so that the assembly of FtsZ-rings, and therefore the cell division, can proceed in a regulated manner. 相似文献
78.
Neelima Arora Amit Kumar Banerjee Srilaxmi Mutyala Upadhyayula Suryanarayana Murty 《Bioinformation》2009,3(10):446-453
Xylanase is an industrially important enzyme having wide range of applications especially in paper industry. It is crucial to gain
an understanding about the structure and functional aspects of various xylanases produced from diverse sources. In this study, a
bioinformatics and molecular modeling approach was adopted to explore properties and structure of xylanases. Physico-chemical
properties were predicted and prediction of motifs, disulfide bridges and secondary structure was performed for functional
characterization. Apart from these analyses, three dimensional structures were constructed and stereo-chemical quality was
evaluated by different structure validation tools. Comparative catalytic site analysis and assessment was performed to extract
information about the important residues. Asn72 was found to be the common residue in the active sites of the proteins
and P35809. Q12603相似文献
79.
Syamantak Majumder K P Tamilarasan Gopi Krishna Kolluru Ajit Muley C Madhavan Nair Athira Omanakuttan K V G K Murty Suvro Chatterjee 《Biochimie et biologie cellulaire》2007,85(6):709-720
Hepatic stellate cells are liver-specific pericytes and exist in close proximity with endothelial cells. The activation of liver pericytes is intrinsic to liver pathogenesis, and leads to endothelial dysfunction, including the low bioavailability of nitric oxide (NO). However, the role of nitric oxide in pericyte-endothelium cross-talk has not yet been elucidated. This work examines the cellular mechanism of action of NO in pericyte-mediated endothelial dysfunction. We used in vitro coculture and conditioned medium systems to study the effects of activated liver pericytes on endothelial function, and an egg yolk vascular bed model was used to study the effects of activated pericytes on angiogenesis. This study also demonstrates that activated pericytes attenuate the migration, proliferation, permeability, and NO production of endothelial cells. Our results demonstrate that activated pericytes restrict angiogenesis in egg yolk vascular bed models, and NO supplementation recovers 70% of the inhibition. Our results also demonstrate that supplementation with NO, sildenafil citrate (phosphodiesterase inhibitor), and 8-bromo-cGMP (cGMP analog) partially recovers activated-pericyte-mediated endothelium dysfunction. We conclude that NO-cGMP alleviates activated-pericyte-associated endothelial dysfunction, including angiogenesis, in a cGMP-dependent manner. 相似文献
80.
The kinetics of enzymatic hydrolysis of rice bran oil in isooctane by immobilized Candida rugosa lipase in a batch reactor showed competitive inhibition by isooctane with a dissociation constant, K1, of 0.92 M. Continuous hydrolysis of rice bran oil was performed in recycling, packed bed reactor with 4352 U of immobilized lipase; the optimum recycle ratio was 9 and the operational half-life was 360 h without isooctane but 288 h with 25% (v/v) isooctane in rice bran oil. 相似文献