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1.
Xinqiang Guo Kai Chen Yang Wen Rong Li Shunpeng Li Jiandong Jiang 《International biodeterioration & biodegradation》2009,63(5):576-581
Bioremediation of pollutants in natural environments is affected by many factors, such as bacterial survival, motility, and chemotaxis. However, these roles in in-situ biodegradation of organophosphorus pesticides have not been examined extensively. In this paper, a highly effective methyl-parathion (MP) degrading strain, Pseudomonas putida DLL-1, which also demonstrates motile ability and chemotactic response toward MP, was selected as the research material. A leuB? auxotroph mutant A3-27 and fliC? non-motility mutant a4-8 were first constructed by random insertion of the kanamycin gene into the chromosome of P. putida DLL-1 with the mini-transposon system. Biodegradation of MP in liquid medium and soil microcosms by A3-27, a4-8 and a previously constructed cheA? non-chemotaxis mutant P. putida DAK were compared. The kinetic parameters for MP degradation were all similar in the well-mixed liquid systems. However, in soil microcosms, all the three mutants had lower degrading rates compared with wild-type P. putida DLL-1. The auxotroph mutant A3-27 had the lowest degrading rate and could only degrade 25.7–34.2% MP in 5 days, and the non-motility mutant a4-8 and non-chemotaxis mutant DAK could only degrade 53.5–68.1% and 64.3–85.7% MP, respectively. This paper emphasizes, for the first time, the use of non-auxotroph bacteria for efficient removal of organophosphorus pesticides in contaminated sites, and also points out the importance of select microorganisms with specific motile or chemotactic affinities in optimizing pesticide bioremediation. 相似文献
2.
《Journal of Fermentation Technology》1988,66(3):365
3.
It has been characterized that the programmed ribosomal ?1 frameshifting often occurs at the slippery sequence on the presence of a downstream mRNA pseudoknot. In some prokaryotic cases such as the dnaX gene of Escherichia coli, an additional stimulatory signal—an upstream, internal Shine–Dalgarno (SD) sequence—is also necessary to stimulate the efficient ?1 frameshifting. However, the molecular and physical mechanism of the ?1 frameshifting is poorly understood. Here, we propose a model of the pathway of the ?1 translational frameshifting during ribosome translation of the dnaX ?1 frameshift mRNA. With the model, the single-molecule fluorescence data (Chen et al. (2014) [29]) on the dynamics of the shunt either to long pausing or to normal translation, the tRNA transit and sampling dynamics in the long-paused rotated state, the EF-G sampling dynamics, the mean rotated-state lifetimes, etc., are explained quantitatively. Moreover, the model is also consistent with the experimental data (Yan et al. (2015) [30]) on translocation excursions and broad branching of frameshifting pathways. In addition, we present some predicted results, which can be easily tested by future optical trapping experiments. 相似文献
4.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(3):601-610
A series of novel 1,4-substituted semicarbazides 5a–g with a primaquine moiety bridged by a carbonyl group at position 1 and a cycloalkyl, aryl, benzyloxy or hydroxy substituent at position 4 were prepared and biologically evaluated. The synthetic pathways applied for preparation of the title compounds involved benzotriazole as synthetic auxiliary. Primaquine semicarbazides 5a–g and their synthetic precursors benzotriazolecarbonyl semicarbazides 4 were evaluated for cytostatic, antiviral and antioxidative activities. All compounds of the series 5 showed high selectivity towards MCF-7 cells (breast carcinoma) with IC50 values in the low micromolar range and the most active was benzyl derivative 5c (IC50 1?±?0.2 µM). The benzhydryl derivative 5e showed significant cytostatic activities towards all the tested cell lines (IC50 4–18 µM). The same compound was the strongest lipoxygenase inhibitor as well (51%). The highest antioxidant activity was demonstrated for the hydroxy derivative 5g and benzotriazolecarbonyl semicarbazides 4b,c (61.2–68.5%). No antiviral activity was observed against a wide variety of DNA and RNA viruses. 相似文献
5.
《Inorganica chimica acta》1988,143(2):209-212
Conductimetric studies of thionyl chloride solutions of ZrCl4 and ZrOCl2·8H2O indicate that the solvated species in the two solutions are different. From such solutions the synthesis of two types of pentachlorozirconates are reported. The synthesis of hexachlorozirconates from each solution is also reported. 相似文献
6.
7.
8.
《Biotechnic & histochemistry》2013,88(6):276-293
To determine changes in the distribution of cell adhesion molecules during diapedesis of monocytes in situ, we labeled aortic whole mounts from hypercholesterolemic rats with Texas red-phalloidin and antibodies to LFA-1, PECAM-1, or α-catenin, and analyzed them by laser scanning confocal microscopy. Monocytes transmigrated through circular openings (transmigration passages) formed by pseudopodia that penetrated between adjacent en-dothelial cells. Transmigrating monocytes remained spherical above the endothelium, while spreading beneath it. The transmigration passage was lined by F-actin and partially by α-catenin, suggesting cadherin-mediated heterotypic interactions. LFA-1 was present in clusters at the monocyte cell surface throughout diapedesis, but was concentrated at the margin of the transmigration passage. PECAM-1 was enriched in the endothelial contact regions where the monocytes transmigrated. PECAM-1 was barely detectable in monocytes before and after diapedesis, but appeared during diapedesis at the cell surface in the parts of the monocyte located above the endothelium. PECAM-1 was enriched near the endothelial cell-cell junctions, but was not detected in parts that spread beneath the endothelium. Our results suggest a major role for LFA-1 during diapedesis and reveal dynamic changes in the distribution of PECAM-1, the actin cytoskeleton, and α-catenin during monocyte diapedesis in situ. 相似文献
9.
Summary Reaction kinetic analysis of the electrical properties of the electrogenic Cl– pump inAcetabularia has been extended from steady-state to nonsteady-state conditions: electrical frequency responses of theAcetabularia membrane have been measured over the range from 1 Hz to 10 kHz at transmembrane potential differences across the plasmalemma (V
m
) between –70 and –240 mV using voltage-clamp techniques. The results are well described by an electrical equivalent circuit with three parallel limbs: a conventional membrane capacitancec
m
, a steadystate conductanceg
o
(predominantly of the pump pathway plus a minor passive ion conductance) and a conductanceg
s
in series with a capacitancec
p
which are peculiar to the temporal behavior of the pump. The absolute values and voltage sensitivities of these four elements have been determined:c
m
of about 8 mF m–2 turned out to be voltage insensitive; it is considered to be normal.g
o
is voltage sensitive and displays a peak of about 80 S m–2 around –180 mV. Voltage sensitivity ofg
s
could not be documented due to large scatter ofg
s
(around 80 S m–2).c
p
behaved voltage sensitive with a notch of about 20 mF m–2 around –180 mV, a peak of about 40 mF m–2 at –120 mV and vanishing at –70 mV. When these data are compared with the predictions of nonsteady-state electrical properties of charge transport systems (U.-P. Hansen, J. Tittor, D. Gradmann, 1983,J. Membrane Biol. in press), model A (redistribution of states within the reaction cycle) consistently provides magnitude and voltage sensitivity of the elementsg
o
,g
s
andc
p
of the equivalent circuit, when known kinetic parameters of the pump are used for the calculations. This analysis results in a density of pump elements in theAcetabularia plasmalemma of about 50 nmol m–2. The dominating rate constants for the redistribution of the individual states of the pump in the electric field turn out to be in the range of 500 sec–1, under normal conditions. 相似文献
10.
Selection of antigen loss variants from the BW5147 cell line after chemical mutagenesis, using antibodies to Thy-1.1, Ly-6.2 and H9/25 allospecificities, produced cell lines with a pleiotropic defect in cell surface antigen expression; selection against any antigen led to the loss of all three determinants. The genetic basis for the mutant phenotype has been analyzed by gene complementation by somatic cell hybridization between Ly-6
– or H9/25
– and Thy-1
– mutants, which comprise different Thy-1 gene complementation classes. The Ly-6
– and H9/25
– mutants can be classified as belonging to either the A or E Thy-1– mutant class. 相似文献
11.
12.
The sensitivity of strains ofEscherichia coli, with and without the RP1 R-factor, to antibiotics and other antibacterial agents has been studied. RP1+ strains ofE. coli were resistant to kanamycin, carbenicillin, and tetracycline, resistance to the first two antibiotics being produced by destruction
of the drugs. This resistance could be transferred to two strains ofPseudomonas aeruginosa. The parent strain ofE. coli UB 1005, its two mutant strains (DC2 and DC3), and two of the strains with the RP1 R-factor showed a similar order of sensitivity
to phenylmercuric nitrate, chlorhexidine, thiomersal, and mercuric chloride.E. coli strains DC2 and DC2 (RP1+) were the most sensitive to benzalkonium chloride and cetrimide. RP1+ strains were more resistant than RP1− strains to lysozyme-ethylenediaminetetraacetic acid, but treatment of the former strains with acriflavine rendered the cells
more sensitive to the lytic system. There was no evidence thatP. aeruginosa (RP1+) strains possessed increased resistance to polymyxin or to disinfectants, although they became somewhat less sensitive to
lysozyme-ethylenediaminetetraacetic acid. 相似文献
13.
Indole-3-acetic acid (IAA) and its putative precursors, l- and d-tryptophan, indole-3-pyruvate, and tryptamine were isolated from tomato (Lycopersicon esculentum (L.) Mill.) shoots, identified by mass spectrometry, and measured using capillary gas chromatography with an electron capture detector and radioactive internal standards. Average amounts present were 7.9ng · (g FW)–-1 IAA, 5.7ng · (g FW)–-1 indole-3-pyruvate, 132 ng · (g FW)–-1 tryptamine, 103 ng · (g FW)–-1
d-tryptophan, and 2250 ng · (g FW)–-1
l-tryptophan. Indole-3-acetaldoxime was not found; detection limits were less than 1ng · (g FW)–-1. When tomato shoots were incubated for 6, 10 and 21 h in 30% –2H2O, up to four positions in IAA, l- and d-tryptophan, tryptamine and indole-3-pyruvate became labelled with –2H. Compounds became labelled rapidly with 10% of IAA molecules containing –2H after 6 h. The percentage of labelled molecules of IAA and l-tryptophan increased up to 10 h but then decreased again, correlating with an increase in the total shoot tryptophan and presumably a result of protein hydrolysis in the excised, slowly senescing tissue. The amount of –2H in d-tryptophan also showed an increase followed by a decrease, but the proportion of labelled molecules was much less than in l-tryptophan and IAA. Tryptamine became labelled initially at a similar rate to IAA but continued to accumulate –2H up to 21 h. We conclude that tryptamine is synthesized from a different pool of tryptophan from that used in IAA synthesis, and is not a major endogenous precursor of IAA in tomato shoots. Indole-3-pyruvate was the most heavily labelled compound after 6 and 10 h incubation (21-h data not available). Furthermore, the proportion of –2H-labelled indole-3-pyruvate molecules was quantitatively consistent with the amount of label in IAA. On the other hand, a quantitative comparison of the IAA turnover rate and the rate of –2H incorporation into both l- and d-tryptophan indicates that IAA is not made from the total shoot pool of either l- or d-tryptophan. Instead IAA appears to be synthesized from a restricted pool which is turning over rapidly and which has access to both newly synthesized tryptophan and that from protein hydrolysis.Abbreviations GC-ecd
gas chromatography with electroncapture detector
- GC-MS
combined gas chromatography-mass spectrometry
- HPLC
high-performance liquid chromatography
- IAA
indole-3-acetic acid
- IAOX
indole-3-acetaldoxime
- IPyA
indole-3-pyruvate
- PFB
pentafluorobenzyl
- RT
retention time
- TNH2
tryptamine
- Trp
tryptophan
- SIM
selected ion monitoring
We wish to thank Ms. Sue Alford for running the mass spectra and Dr Harry Young for advice with the mass spectrometry. The work was supported by grants from the University of Auckland Research Committee and the C. Alma Baker Trust fund. The mass spectrometer was supported jointly by the University Grants Commitee (NZ) and the DSIR Division of Horticulture and Processing. 相似文献
14.
Summary Changes in extracellular pH (pHo) in red cell suspensions were monitored in a stopped-flow rapid reaction apparatus under conditions wheredpHo/dt was determined by the rate of HCO
3
–
/Cl– exchange across the membrane. Experiments were performed at 5°C<T<40°C using either untreated cells or cells exposed to 0.11mm SITS (4-acetamido-4-isothiocyanostilbene-2,2-disulfonic acid). Although SITS exposure reduced the rate of exchange by 90%, both untreated and SITS-treated cells are similarly affected by changes in pH0 and temperature. The rate of HCO
3
–
/Cl– exchange exhibits a minimum at about pHo 5 and a maximum at about pH0 7.4 at all temperatures. A transition temperature of 17°C was observed in the Arrhenius relationship for all pH0. The activation energies (E
a) in kcal/mol are 19.6 below and 11.7 above 17°C for 50<8. These findings, similar to those reported for Cl– self-exchange, suggest that: (i) a change in the rate-limiting step for HCO
3
–
/Cl– exchange occurs at 17°C, possibly due to an altered interaction between the transport pathway and membrane lipids; (ii) the carrier system can be titrated by either H+ or SITS from the outside of the membrane, but the untitrated sites continue to transport normally; (iii) the pH0 dependence of the rate of exchange is consistent with the titratable carrier having its most alkaline pK in the range expected for amino groups; and (iv) below pH0 5, the nature of the exchange is markedly altered. 相似文献
15.
16.
Medium chain β-1-alkylglycosides show interesting mild detergent properties. Therefore, their synthesis and purification have been investigated and improved so as to permit preparation of 50–100 g amounts. Preparatory methods are presented for the already known compounds β-1-octyl-, β-1-nonyl and β-1-decyl-glucose and for the new compounds β-1-undecylglucose and β-1-dodecylmaltose. Some relevant properties such as melting point, optical rotation, critical micelle concentration and NMR-spectra have been determined. They illustrate the suitability of this class of detergents for membrane research. 相似文献
17.
Mikhail L. Antonkine Detlef Bentrop Ivano Bertini Claudio Luchinat Gaozhong Shen Donald A. Bryant Dietmar Stehlik John H. Golbeck 《Journal of biological inorganic chemistry》2000,5(3):381-392
A and FB. The g-tensor orientation of FA
− and FB
− is believed to be correlated to the preferential localization of the mixed-valence and equal-valence (ferrous) iron pairs
in each [4Fe-4S]+ cluster. The preferential position of the mixed-valence and equal-valence pairs, in turn, can be inferred from the study
of the temperature dependence of contact-shifted resonances by 1H NMR spectroscopy. For this, a sequence-specific assignment of these signals is required. The 1H NMR spectrum of reduced, unbound PsaC from Synechococcus sp. PCC 7002 at 280.4 K in 99% D2O solution shows 18 hyperfine-shifted resonances. The non-solvent-exchangeable, hyperfine-shifted resonances of reduced PsaC
are clearly identified as belonging to the cysteines coordinating the clusters FA
− and FB
− by their downfield chemical shifts, by their temperature dependencies, and by their short T
1 relaxation times. The usual fast method of assigning the 1H NMR spectra of reduced [4Fe-4S] proteins through magnetization transfer from the oxidized to the reduced state was not feasible
in the case of reduced PsaC. Therefore, a de novo self-consistent sequence-specific assignment of the hyperfine-shifted resonances was obtained based on dipolar connectivities
from 1D NOE difference spectra and on longitudinal relaxation times using the X-ray structure of Clostridium acidi urici 2[4Fe-4S] cluster ferredoxin at 0.94 Å resolution as a model. The results clearly show the same sequence-specific distribution
of Curie and anti-Curie cysteines for unbound, reduced PsaC as established for other [4Fe-4S]-containing proteins; therefore,
the mixed-valence and equal-valence (ferrous) Fe-Fe pairs in FA
− and FB
− have the same preferential positions relative to the protein. The analysis reveals that the magnetic properties of the two
[4Fe-4S] clusters are essentially indistinguishable in unbound PsaC, in contrast to the PsaC that is bound as a component
of the PS I complex.
Received: 1 February 2000 / Accepted: 20 March 2000 相似文献
18.
C. A. Rotunno M. V. Ques-von Petery M. Cereijido 《The Journal of membrane biology》1978,42(4):331-343
Summary At low concentration (1mm) of Cl– in the outer solution, the influx of chloride through the isolated skin (J
13
Cl
) of the South American frogLeptodactylus ocellatus (L.) seems to be carried by two mechanisms: (i) a passive one that exhibits the characteristics of an exchange diffusion process, and (ii) an active penetration. Studies of the influx and efflux of chloride (J
13
Cl
andJ
31
Cl
) indicate, that the presence of a high (107mm) concentration of Cl– in the outer solution activates the translocation of this ion through the cells. Studies of the unidirectional flux of Cl– across the outer barrier (J
12
Cl
) indicate that Na+ out stimulates the penetration of Cl– at this level. Cl– out, in turn, stimulates, theJ
12
Na
, but this effect is only detected at low concentrations of Na+ out. 相似文献
19.
Kaisa M. Linderborg Gunveen Kaur Eliza Miller Peter J. Meikle Amy E. Larsen Jacquelyn M. Weir Anu Nuora Christopher K. Barlow Heikki P. Kallio David Cameron-Smith Andrew J. Sinclair 《Prostaglandins, leukotrienes, and essential fatty acids》2013,88(4):313-319
The study of the metabolism of docosapentaenoic acid (DPA, 22:5n?3) in humans has been limited by the unavailability of pure DPA and the fact that DPA is found in combination with eicosapentaenoic acid (EPA, 20:5n?3) and docosahexaenoic acid (DHA, 22:6n?3) in natural products. In this double blind cross over study, pure DPA and EPA were incorporated in meals served to healthy female volunteers. Mass spectrometric methods were used to study the chylomicron lipidomics. Plasma chylomicronemia was significantly reduced after the meal containing DPA compared with the meal containing EPA or olive oil only. Both EPA and DPA were incorporated into chylomicron TAGs, while there was less incorporation into chylomicron phospholipids. Lipidomic analysis of the chylomicron TAGs revealed the dynamic nature of chylomicron TAGs. The main TAG species that EPA and DPA were incorporated into were EPA/18:1/18:1, DPA/18:1/16:0 and DPA/18:1/18:1. There was very limited conversion of DPA and EPA to DHA and there were no increases in EPA levels during the 5 h postprandial period after the DPA meal. In conclusion, EPA and DPA showed different metabolic fates, and DPA hindered the digestion, ingestion or incorporation into chylomicrons of the olive oil present in the meal. 相似文献