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61.
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63.
The linked-atom-least-squares (LALS) technique has been applied to generate exactly cyclized and stereochemically satisfactory conformations of the cyclic pentapeptide, malformin A, which contains an intramolecular disulfide bridge across a D-Cys—D-Cys linkage. Consistent with theoretical, ir, and x-ray evidence from studies on analogs of the LKiysteinyl—L-cysteine disulfide, it is shown that the peptide bond across the S? S bridge in malformin A can retain a cis configuration. The two all-trans structures proposed earlier by A.E. Tonelli [(1978) Biopolymers 17, 1175–1179] from solution nmr data have also been analyzed. Both P-(χs ~ 90°) and M-(χs ~ ?90°)-type helicity of the S? S bridge are found to be accessible in both the trans and the cis models in which the respective conformations of the homodetic rings are essentially preserved. The details of six different conformational states and their relative energies have been evaluated and compared. Our findings, which suggest that a variety of conformational states are accessible to malformin A, are compatible with other published results from solution studies. On the basis of hydrogen-bonding interactions, a model is proposed to explain how malformin A might be inactivated specifically by L -Hyp, and not by L -Pro or other amino acids, as has been observed from in vivo investigations [Buckhout, T.J. & Curtis, R.W. (1976) Nature 260 , 435–436] 相似文献
64.
Transfer and Expression of a Multiple Antibiotic Resistance Plasmid in Marine Bacteria 总被引:1,自引:0,他引:1
Subramanian Chandrasekaran Balakrishnan Venkatesh Damodharan Lalithakumari 《Current microbiology》1998,37(5):347-351
Conjugal transfer of a multiresistance plasmid from Pseudomonas fluorescens to halophilic and halotolerant bacteria was studied under in vitro and in situ conditions. Mating conducted in broth as well
as on plates yielded a plasmid transfer frequency of as high as 10−3. Among these two, plate mating facilitated conjugal transfer of plasmid, because the cell-to-cell contact is more in plate
mating. When P. fluorescens was incubated in seawater, the organism progressively lost its colony forming activity within 15 days. Microscopic examination
revealed the presence of very short rods, indicating that the cells have become viable but nonculturable (VNC). Mating conducted
in natural seawater without any added nutrients revealed that the conjugal transfer is influenced by the physical state of
the donor and the recipients as well as the availability of nutrients. But a plasmid transfer frequency of 10−7 was obtained even after the donor cells have become VNC suggesting that the nonculturable state and nutrient deprived condition
may not limit plasmid transfer. The results suggest that the terrestrial bacteria entering into the seawaters with antibiotic
resistance plasmids may be responsible for the prevalence of resistance genes in the marine environment.
Received: 4 May 1998 / Accepted: 18 June 1998 相似文献
65.
Murugesan Chandrasekaran 《Biocontrol Science and Technology》2016,26(10):1366-1378
Bacterial spot disease caused by Xanthomonas campestris pv. vesicatoria is one of the most important destructive diseases of tomato in many parts of the agricultural world. Therefore, the present study aims to determine the effects of Bacillus subtilis CBR05 inoculation on bacterial spot disease severity and the induction of defence-related enzymes response in tomato. Tomato leaves were evaluated to determine the activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and polyphenol oxidase (PPO)) and the content of malondialdehyde (MDA). A reduction in bacterial spot severity was observed in plants inoculated with B. subtilis, compared with those of uninoculated controls. A significant increase in SOD, CAT, POD, and PPO activities was observed in plants treated with B. subtilis after 24?h inoculation compared with non-inoculated pathogen control and mock-inoculated controls. Moreover, the MDA content was induced by pathogen infection, and its amount in B. subtilis inoculated plants was significantly lower than that in pathogen control. Our results suggest that early increases in antioxidant enzymes and the reduction in MDA content with B. subtilis inoculation may play a pivotal role in mitigating oxidative stress, thereby induced systemic resistance against bacterial spot disease in tomato. 相似文献
66.
Yousuf Sameena Sowrirajan Chandrasekaran 《Journal of biomolecular structure & dynamics》2016,34(7):1395-1408
This work deals with the commonly studied cyclic oligosaccharide and gains importance as it is entered on a drug delivering carbohydrate and provides insight into the oligosaccharide complex–biomolecular interaction. The binding of a flavone, baicalein, to β-cyclodextrin and calf thymus DNA is studied. The binding of baicalein to calf thymus DNA in the presence of β-cyclodextrin is analysed using the UV–vis absorption and fluorescence spectroscopy. The mode of binding and structure of the baicalein–β-cyclodextrin complex are reported. The role of the structure and the stoichiometry of the inclusion complex of baicalein–β-cyclodextrin in its influence on DNA binding are analysed.Highlights? This paper deals with the binding of a flavone, baicalein to β-cyclodextrin and/or DNA.? The inclusion complexation between baicalein and β-cyclodextrin is analysed.? The stoichiometry and the binding strength of the inclusion complex is reported.? The role of β-cyclodextrin in tuning the binding of baicalein to DNA is emphasized.? Spectroscopic and docking analysis are used to articulate the results. 相似文献
67.
68.
K. Sapna P. P. Manzur Ali K. R. Rekha Mol Sarita G. Bhat M. Chandrasekaran K. K. Elyas 《Biotechnology letters》2017,39(12):1911-1916
Objectives
An extracellular protease inhibitor (BTPI-301) of trypsin was purified and characterized from an isolate of Pseudomonas mendocina.Results
BTPI-301was purified to homogeneity by (NH4)2SO4, precipitation, DEAE Sepharose and CNBr-activated Sepharose chromatography. Homogeneity was proved by native PAGE and SDS-PAGE. The intact molecular mass was 11567 Da by MALDI-TOF analysis. BTPI-301was a competitive inhibitor with a Ki of 3.5 × 10?10 M. It was stable and active at pH 4–12 and also at 4–90 °C for 1 h. Peptide mass fingerprinting by MALDI revealed that the BTPI-301 is a new inhibitor not reported so far with protease inhibitory activity. The pI of the inhibitor was 3.8. The stoichiometry of trypsin-BTPI-301 interaction is 1:1. The inhibitor was specific towards trypsin.Conclusion
A pH tolerant and thermostable protease inhibitor BTPI-301 active against trypsin was purified and characterized from P. mendocina that could be developed and used as biopreservative as well as biocontrol agent.69.
Prabukumar Seetharaman Sathishkumar Gnanasekar Rajkuberan Chandrasekaran Gobinath Chandrakasan Murugan Kadarkarai Sivaramakrishnan Sivaperumal 《Annals of microbiology》2017,67(4):321-331
Chrysin (5,7-dihydroxy flavone, ChR) is a flavone of plant origin, possessing numerous biomedical properties, such as antimicrobial, anti-inflammatory, anti-diabetic, anxiolytic, hepatoprotective, anti-aging and anticonvulsant activities. In this study, chrysin-producing fungal endophytes (A. alternata KT380662, C. capsici KT373967, and C. taiwanense PI-3 KX580307) were isolated from the leaves of Passiflora incarnata L. and characterised via morphology and internal transcribed spacer (ITS) sequences. Thin layer chromatography and high-performance liquid chromatography profiles of fungal extracts showed Rf values and retention times that closely match those of standard chrysin (ChR). Further, the production of fungal chrysin (FChR) was confirmed through UV-vis spectroscopy, FT-IR, LC-ESI-MS, and 1H1 NMR analysis. Among the isolated strains, A. alternata KT380662 was identified as having a high-level of ChR production, with rates measuring approximately 846 mg L?1. On the other hand, in vitro anticancer and radical scavenging studies proved that FChR has significant cytotoxic activity against human liver carcinoma cells (HepG2). These results clearly imply that the isolated A. alternata KT380662 could serve as an alternative source for the commercial production of ChR, which holds anticancer and radical scavenging activities, and the fungal-derived ChR can be used in chemotherapy or in prodrug development. 相似文献
70.
Das U Molnár J Baráth Z Bata Z Dimmock JR 《Bioorganic & medicinal chemistry letters》2008,18(12):3484-3487
The 1-[4-(2-aminoethoxy)phenylcarbonyl]-3,5-bis-(benzylidene)-4-oxopiperidines 5-8 are a novel cluster of highly potent P-glycoprotein dependent multidrug resistance (MDR) revertants. Using a concentration of 4mug/mL, these compounds possess 11-43 times the potency of verapamil in reversing MDR in murine L-5178 lymphoma cells transfected with the human MDR1 gene. Structure-activity relationships reveal that the attachment of the N-aroyl group to various 3,5-bis(benzylidene)-4-piperidones is essential for MDR reversal to occur. In terms of potencies, the 1-piperidinyl group is the preferred terminal amine while the 4-methyl and 4-chloro substituents are the optimal groups for placement in the benzylidene aryl rings. 相似文献