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On-line fluorescence-monitoring of the methanogenic fermentation 总被引:2,自引:0,他引:2
On-line in situ fluorescence measurements of the methanogenic fermentation were conducted with reactors receiving either glucose or a mixture of volatile fatty acids as the substrate. The reactors were perturbed from steady-state conditions in order to assess the response of fluorescencemonitoring probes. Two fluorescence-monitoring probes were evaluated over a period of 8 months; they performed in a consistent manner, and their response was not significantly affected by the changes in pH and redox potential encountered during routine reactor operation. A commercially available probe, designed to measure NAD(P)H, demonstrated particular promise for detecting imbalance caused by the entry of air, inhibitor addition and was capable of distinguishing between different substrates. This fluorescence-monitoring probe detected imbalance more rapidly than other on-line measurements such as pH, Eh, or gas production, or off-line measurements such as volatile fatty acid concentration or gas composition. An experimental fluorescence-monitoring probe, designed to measure coenzyme F(420), also showed some promise in this regard. The response of the fluorescence-monitoring probes also revealed details of the metabolic routes in the reactors and the probes represent a useful research tool. For example, a failure to observe the characteristic response of the NAD(P)H-monitoring probe to formate addition during the metabolism of acetate, propionate, or glucose strongly suggests that any formate liberated during their catabolism is degraded via a different route to exogenously added formate. 相似文献
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Comparison of In Situ and In Vitro Rates of Methane Release in Freshwater Sediments 总被引:6,自引:4,他引:2
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Anaerobic lake sediment incubated in vitro was investigated for its ability to mimic natural in situ sediment activities, using rate of methane production for the comparison. Two lakes with different rates and seasonal patterns of methanogenic activity were compared. There was good agreement (at the 97.5% confidence level) between rates of in situ methane release and initial (lasting an average of 120 h) rates of production measured in vitro in surface (0- to 3-cm) sediment. Evidence from this study, and others, indicated that it is the in situ surface sediment methane production which is primarily responsible for maintaining in situ methane release, and thus the above agreement was what was expected if surface in situ activity was maintained in vitro. When deeper sediment was investigated, however, the sum of in vitro rates from 0 to 20 cm (measured in 1.5- to 3-cm intervals) was much higher than in situ release rates and would have resulted in an impossibly high volume of gas. The extra gas could not have been stored within the sediments. We conclude that the in situ methanogenic activity of the 0- to 3-cm anaerobic surface sediments could be preserved during removal and laboratory incubation. However, similar treatment of deeper sediment appeared to stimulate methanogenic activity. 相似文献
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Intrinsic protein fluorescence may interfere with the visualization of proteins after SDS-polyacrylamide electrophoresis. In an attempt to analyze tear glycoproteins in gels, we ran tear samples and stained the proteins with a glycoprotein-specific fluorescent dye. The fluorescence detected was not limited to glycoproteins. There was strong intrinsic fluorescence of proteins normally found in tears after soaking the gels in 40% methanol plus 1-10% acetic acid and, to a lesser extent, in methanol or acetic acid alone. Nanograms of proteins gave visible native fluorescence and interfere with extrinsic fluorescent dye detection. Poly-L-lysine, which does not contain intrinsically fluorescent amino acids, did not fluoresce. 相似文献
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Cifuentes D Chynoweth R Guillén J De la Rúa P Bielza P 《Journal of economic entomology》2012,105(3):1006-1018
Control of Frankliniella occidentalis (Pergande) is a serious problem for agriculture all over the world because of the limited range of insecticides that are available. Insecticide resistance in F. occidentalis has been reported for all major insecticide groups. Our previous studies showed that cytochrome P450-mediated detoxification is a major mechanism responsible for insecticide resistance in this pest. Degenerate polymerase chain reaction was used to identify P450 genes that might be involved in acrinathrin resistance, in a laboratory population of F. occidentalis. Associated sequences were classified as belonging to the CYP4 and CYP6 families. Real-time quantitative polymerase chain reaction analyses revealed that two genes, CYP6EB1 and CYP6EC1, were over-expressed in adults and L2 larvae of the resistant population, when compared with the susceptible population, suggesting their possible involvement in resistance to acrinathrin. 相似文献
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A study of bacterial surface oligosaccharides were investigated among
different strains of Neisseria gonorrhoeae to correlate structural features
essential for binding to the MAb 2C7. This epitope is widely expressed and
conserved in gonococcal isolates, characteristics essential to an effective
candidate vaccine antigen. Sample lipooligosaccharides (LOS), was prepared
by a modification of the hot phenol-water method from which de-O-acetylated
LOS and oligosaccharide (OS) components were analyzed by ES-MS-CID-MS and
ES-MSnin a triple quadrupole and an ion trap mass spectrometer,
respectively. Previously documented natural heterogeneity was apparent from
both LOS and OS preparations which was admixed with fragments induced by
hydrazine and mild acid treatment. Natural heterogeneity was limited to
phosphorylation and antenni extensions to the alpha-chain. Mild acid
hydrolysis to release OS also hydrolyzed the beta(1-->6) glycosidic
linkage of lipid A. OS structures were determined by collisional and
resonance excitation combined with MS and multistep MSn which provided
sequence information from both neutral loss, and nonreducing terminal
fragments. A comparison of OS structures, with earlier knowledge of MAb
binding, enzyme treatment, and partial acid hydrolysis indicates a generic
overlapping domain for 2C7 binding. Reoccurring structural features include
a Hepalpha(1-->3)Hepbeta(1-->5)KDO trisaccharide core branched on the
nonreducing terminus (Hep-2) with an alpha(1-->2) linked GlcNAc
(gamma-chain), and an alpha-linked lactose (beta-chain) residue. From the
central heptose (Hep-1), a beta(1-->4) linked lactose (alpha-chain),
moiety is required although extensions to this residue appear unnecessary.
相似文献
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Thomas GH; Newbern EC; Korte CC; Bales MA; Muse SV; Clark AG; Kiehart DP 《Molecular biology and evolution》1997,14(12):1285-1295
Many structural, signaling, and adhesion molecules contain tandemly
repeated amino acid motifs. The alpha-actinin/spectrin/dystrophin
superfamily of F-actin-crosslinking proteins contains an array of triple
alpha-helical motifs (spectrin repeats). We present here the complete
sequence of the novel beta-spectrin isoform beta(Heavy)- spectrin (beta H).
The sequence of beta H supports the origin of alpha- and beta-spectrins
from a common ancestor, and we present a novel model for the origin of the
spectrins from a homodimeric actin-crosslinking precursor. The pattern of
similarity between the spectrin repeat units indicates that they have
evolved by a series of nested, nonuniform duplications. Furthermore, the
spectrins and dystrophins clearly have common ancestry, yet the repeat unit
is of a different length in each family. Together, these observations
suggest a dynamic period of increase in repeat number accompanied by
homogenization within each array by concerted evolution. However, today,
there is greater similarity of homologous repeats between species than
there is across repeats within species, suggesting that concerted evolution
ceased some time before the arthropod/vertebrate split. We propose a
two-phase model for the evolution of the spectrin repeat arrays in which an
initial phase of concerted evolution is subsequently retarded as each new
protein becomes constrained to a specific length and the repeats diverge at
the DNA level. This evolutionary model has general applicability to the
origins of the many other proteins that have tandemly repeated motifs.
相似文献
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Background
Dihydroartemisinin-piperaquine (DP) is increasingly recommended for antimalarial treatment in many endemic countries; however, concerns have been raised over its potential under dosing in young children. We investigated the influence of different dosing schedules on DP''s clinical efficacy.Methods and Findings
A systematic search of the literature was conducted to identify all studies published between 1960 and February 2013, in which patients were enrolled and treated with DP. Principal investigators were approached and invited to share individual patient data with the WorldWide Antimalarial Resistance Network (WWARN). Data were pooled using a standardised methodology. Univariable and multivariable risk factors for parasite recrudescence were identified using a Cox''s regression model with shared frailty across the study sites. Twenty-four published and two unpublished studies (n = 7,072 patients) were included in the analysis. After correcting for reinfection by parasite genotyping, Kaplan–Meier survival estimates were 97.7% (95% CI 97.3%–98.1%) at day 42 and 97.2% (95% CI 96.7%–97.7%) at day 63. Overall 28.6% (979/3,429) of children aged 1 to 5 years received a total dose of piperaquine below 48 mg/kg (the lower limit recommended by WHO); this risk was 2.3–2.9-fold greater compared to that in the other age groups and was associated with reduced efficacy at day 63 (94.4% [95% CI 92.6%–96.2%], p<0.001). After adjusting for confounding factors, the mg/kg dose of piperaquine was found to be a significant predictor for recrudescence, the risk increasing by 13% (95% CI 5.0%–21%) for every 5 mg/kg decrease in dose; p = 0.002. In a multivariable model increasing the target minimum total dose of piperaquine in children aged 1 to 5 years old from 48 mg/kg to 59 mg/kg would halve the risk of treatment failure and cure at least 95% of patients; such an increment was not associated with gastrointestinal toxicity in the ten studies in which this could be assessed.Conclusions
DP demonstrates excellent efficacy in a wide range of transmission settings; however, treatment failure is associated with a lower dose of piperaquine, particularly in young children, suggesting potential for further dose optimisation. Please see later in the article for the Editors'' Summary 相似文献10.