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961.
962.
963.
M. T. Johnson N. Greenwood D. B. Sivyer M. Thomson A. Reeve K. Weston T. D. Jickells 《Biogeochemistry》2013,113(1-3):23-36
The Cefas SmartBuoy network provides a unique insight into the biogeochemical dynamics of the Northern European shelf seas, particularly the North Sea, through high-resolution automated offshore water sampling. We present total dissolved nitrogen and dissolved organic nitrogen (DON) from the Dowsing SmartBuoy site (53.531° N, 1.053° E) from January to October 2010, the first high resolution seasonal (winter-autumn) cycle of DON from the open North Sea. On top of a refractory background DON concentration of approximately 5 μM, a rapid increase in DON of a further ~5 μM is observed over the course of the spring bloom. This rapidly produced DON declines at an estimated net decay rate of between 0.6 and 1.8 μM month?1. The slow decay suggests that the majority of the additional DON produced during the spring bloom is of semi-labile nature and has a lifetime of weeks to months. The dataset allows us to tightly constrain the budget for water column nitrogen over the winter, spring and summer of 2010 and clearly demonstrates the ‘sawtooth’ nature of the seasonal cycle of DON in the open North Sea, which has been impossible to resolve with a more traditional ship-based mode of operation. This work highlights the importance of autonomous sampling approaches in better understanding shelf sea biogeochemistry in the future. 相似文献
964.
Kevin McClay Baojie Wan Yuehong Wang Sanghyun Cho Jerry Yu Bernard Santarsiero Shahila Mehboob Michael Johnson Scott Franzblau Robert Steffan 《Applied microbiology and biotechnology》2013,97(16):7151-7163
Two bacterial hosts expressing cloned aromatic oxygenases were used to catalyze the oxidation and polymerization of indole and related substrates, creating mixtures of indigoid compounds comprised of novel dimers and trimers. Crude extracts and purified compounds were tested for their ability to inhibit the growth of Gram-positive organisms, in general, and Mycobacterium tuberculosis (TB), in particular. Of the 74 compounds tested against M. tuberculosis, ~66 % had minimum inhibitory concentrations (MIC) of 5 μg/ml or less. The most effective antibiotic found was designated SAB-P1, a heterodimer of indole and anthranil, which had a MIC of 0.16 μg/ml, and did not inhibit kidney cells (IC50) at concentrations of >8 μg/ml. Combinatorial biocatalysis was used to create a series of halogenated derivatives of SAB-P1 with a wider therapeutic window. None of the derivatives had MIC values that were superior to SAB-P1, but some had a wider therapeutic window because of decreased kidney cell toxicity. Generally, the indigoid dimers that were effective against TB appeared to be specific for TB. Some of the trimers generated, however, had a broader spectrum of activity inhibiting not only TB (MIC?=?1.1 μg/ml) but also the growth of Mycobacterium smegmatis MC2 155, Bacillus cereus, Enterococcus faecalis, Staphylococcus epidermidis, Bacillus subtilis 168, and Clostridium acetobutylicum. The structure of two of the novel dimers (SAB-C4 and SAB-P1) and a trimer (SAB-R1) were solved using X-ray crystallography. 相似文献
965.
Gerrit J. Poelarends Hector Serrano Jamison P. Huddleston William H. Johnson Jr.Christian P. Whitman 《FEBS letters》2013
trans-3-Chloroacrylic acid dehalogenase (CaaD) catalyzes the hydrolytic dehalogenation of trans-3-haloacrylates to yield malonate semialdehyde by a mechanism utilizing βPro-1, αArg-8, αArg-11, and αGlu-52. These residues are implicated in a promiscuous hydratase activity where 2-oxo-3-pentynoate is processed to acetopyruvate. The roles of three nearby residues (βAsn-39, αPhe-39, and αPhe-50) are unexplored. Mutants were constructed at these positions (βN39A, αF39A, αF39T, αF50A and αF50Y) and kinetic parameters determined along with those of the αR8K and αR11K mutants. Analysis indicates that αArg-8, αArg-11, and βAsn-39 are critical for dehalogenase activity whereas αArg-11 and αPhe-50 are critical for hydratase activity. Docking studies suggest structural bases for these observations. 相似文献
966.
William Johnson Nagalla Balakrishna Paula L. Griffiths 《American journal of physical anthropology》2013,150(1):58-67
This article demonstrates the use of mixed effects models for characterizing individual and sample average growth curves based on serial anthropometric data. These models are advancement over conventional general linear regression because they effectively handle the hierarchical nature of serial growth data. Using body weight data on 70 infants in the Born in Bradford study, we demonstrate how a mixed effects model provides a better fit than a conventional regression model. Further, we demonstrate how mixed effects models can be used to explore the influence of environmental factors on the sample average growth curve. Analyzing data from 183 infant boys (aged 3–15 months) from rural South India, we show how maternal education shapes infant growth patterns as early as within the first 6 months of life. The presented analyses highlight the utility of mixed effects models for analyzing serial growth data because they allow researchers to simultaneously predict individual curves, estimate sample average curves, and investigate the effects of environmental exposure variables. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
967.
Dihydroorotase (DHOase) is the third enzyme in the de novo pyrimidine biosynthesis pathway and is a potential new antibacterial drug target. No target-based high-throughput screening (HTS) assay for this enzyme has been reported to date. Here, we optimized two colorimetric-based enzymatic assays that detect the ureido moiety of the DHOase substrate, carbamyl-aspartate (Ca-asp). Each assay was developed in a 40-μl assay volume using 384-well plates with a different color mix, diacetylmonoxime (DAMO)–thiosemicarbazide (TSC) or DAMO–antipyrine. The sensitivity and color interference of both color mixes were compared in the presence of common HTS buffer additives, including dimethyl sulfoxide, reducing agents, detergents, and bovine serum albumin. DAMO–TSC (Z′-factors 0.7–0.8) was determined to be superior to DAMO–antipyrine (Z′-factors 0.5–0.6) with significantly less variability within replicates. An HTS pilot screening with 29,552 compounds from four structurally diverse libraries confirmed the quality of our newly optimized colorimetric assay with DAMO–TSC. This robust method has no heating requirement, which was the main obstacle to applying previous assays to HTS. More important, this well-optimized HTS assay for DHOase, the first of its kind, should make it possible to screen large-scale compound libraries to develop new inhibitors against any enzymes that produce ureido functional groups. 相似文献
968.
969.
The Water Framework Directive (WFD) requires EU Member States to classify the ecological status of surface waters by using multiple biological quality elements (BQEs). According to the WFD Classification Guidance, a ‘one-out-all-out’ (OOAO) rule should be applied when integrating multiple BQEs into an overall biological status of a waterbody, i.e. classification is determined by the lowest status BQE. Using both simulated and monitoring datasets, we analyzed the effects of different combination rules in classification outcome and classification reliability. The OOAO represented the strictest combination rule in terms of increased probabilities of waterbodies being in moderate or worse status in comparison to other rules. The OOAO approach gave acceptable results when different BQEs were complementary, showing the effects of different pressures, and when level of uncertainty in the metrics used in the assessment was not high. Increasing the number of BQEs used in the assessment affected the classification outcome when using the OOAO approach; this was especially problematic if all BQEs address the same pressure. Our study showed that grouping of metrics and metrics uncertainty has a large influence on classification outcomes and that this should be carefully considered to ensure that final classification adequately reflects ecological status. 相似文献
970.
Zhe Liang Viktor Demko Robert C. Wilson Kenneth A. Johnson Rafi Ahmad Pierre‐François Perroud Ralph Quatrano Sen Zhao Kamran Shalchian‐Tabrizi Marisa S. Otegui Odd‐Arne Olsen Wenche Johansen 《The Plant journal : for cell and molecular biology》2013,75(5):742-754
DEK1, the single calpain of land plants, is a member of the ancient membrane bound TML–CysPc–C2L calpain family that dates back 1.5 billion years. Here we show that the CysPc–C2L domains of land plant calpains form a separate sub‐clade in the DEK1 clade of the phylogenetic tree of plants. The charophycean alga Mesostigma viride DEK1‐like gene is clearly divergent from those in land plants, suggesting that a major evolutionary shift in DEK1 occurred during the transition to land plants. Based on genetic complementation of the Arabidopsis thaliana dek1‐3 mutant using CysPc–C2L domains of various origins, we show that these two domains have been functionally conserved within land plants for at least 450 million years. This conclusion is based on the observation that the CysPc–C2L domains of DEK1 from the moss Physcomitrella patens complements the A. thaliana dek1‐3 mutant phenotype. In contrast, neither the CysPc–C2L domains from M. viride nor chimeric animal–plant calpains complement this mutant. Co‐evolution analysis identified differences in the interactions between the CysPc–C2L residues of DEK1 and classical calpains, supporting the view that the two enzymes are regulated by fundamentally different mechanisms. Using the A. thaliana dek1‐3 complementation assay, we show that four conserved amino acid residues of two Ca2+‐binding sites in the CysPc domain of classical calpains are conserved in land plants and functionally essential in A. thaliana DEK1. 相似文献