307 research outputs found
Single nucleotide polymorphisms of one-carbon metabolism and cancers of the esophagus, stomach, and liver in a Chinese population.
One-carbon metabolism (folate metabolism) is considered important in carcinogenesis because of its involvement in DNA synthesis and biological methylation reactions. We investigated the associations of single nucleotide polymorphisms (SNPs) in folate metabolic pathway and the risk of three GI cancers in a population-based case-control study in Taixing City, China, with 218 esophageal cancer cases, 206 stomach cancer cases, 204 liver cancer cases, and 415 healthy population controls. Study participants were interviewed with a standardized questionnaire, and blood samples were collected after the interviews. We genotyped SNPs of the MTHFR, MTR, MTRR, DNMT1, and ALDH2 genes, using PCR-RFLP, SNPlex, or TaqMan assays. To account for multiple comparisons and reduce the chances of false reports, we employed semi-Bayes (SB) shrinkage analysis. After shrinkage and adjusting for potential confounding factors, we found positive associations between MTHFR rs1801133 and stomach cancer (any T versus C/C, SB odds-ratio [SBOR]: 1.79, 95% posterior limits: 1.18, 2.71) and liver cancer (SBOR: 1.51, 95% posterior limits: 0.98, 2.32). There was an inverse association between DNMT1 rs2228612 and esophageal cancer (any G versus A/A, SBOR: 0.60, 95% posterior limits: 0.39, 0.94). In addition, we detected potential heterogeneity across alcohol drinking status for ORs relating MTRR rs1801394 to esophageal (posterior homogeneity P = 0.005) and stomach cancer (posterior homogeneity P = 0.004), and ORs relating MTR rs1805087 to liver cancer (posterior homogeneity P = 0.021). Among non-alcohol drinkers, the variant allele (allele G) of these two SNPs was inversely associated with the risk of these cancers; while a positive association was observed among ever-alcohol drinkers. Our results suggest that genetic polymorphisms related to one-carbon metabolism may be associated with cancers of the esophagus, stomach, and liver. Heterogeneity across alcohol consumption status of the associations between MTR/MTRR polymorphisms and these cancers indicates potential interactions between alcohol drinking and one-carbon metabolic pathway
Effect of dispersion on indistinguishability between single-photon wave-packets
With propagating through a dispersive medium, the temporal-spectral profile
of laser pulses should be inevitably modified. Although such dispersion effect
has been well studied in classical optics, its effect on a single-photon
wave-packet, i.e., the matter wave of a single-photon, has not yet been
entirely revealed. In this paper, we investigate the effect of dispersion on
indistinguishability of single-photon wave-packets through the Hong-Ou-Mandel
(HOM) interference. By dispersively manipulating two indistinguishable
single-photon wave-packets before interfering with each other, we observe that
the difference of the second-order dispersion between two optical paths of the
HOM interferometer can be mapped to the interference curve, indicating that (1)
with the same amount of dispersion effect in both paths, the HOM interference
curve must be only determined by the intrinsic indistinguishability between the
wave-packets, i.e., dispersion cancellation due to the indistinguishability
between Feynman paths; (2) unbalanced dispersion effect in two paths cannot be
cancelled and will broaden the interference curve thus providing a way to
measure the second-order dispersion coefficient. Our results suggest a more
comprehensive understanding of the single-photon wave-packet and pave ways to
explore further applications of the HOM interference
Identification and characterization of a novel fumarase gene by metagenome expression cloning from marine microorganisms
<p>Abstract</p> <p>Background</p> <p>Fumarase catalyzes the reversible hydration of fumarate to <smcaps>L</smcaps>-malate and is a key enzyme in the tricarboxylic acid (TCA) cycle and in amino acid metabolism. Fumarase is also used for the industrial production of <smcaps>L</smcaps>-malate from the substrate fumarate. Thermostable and high-activity fumarases from organisms that inhabit extreme environments may have great potential in industry, biotechnology, and basic research. The marine environment is highly complex and considered one of the main reservoirs of microbial diversity on the planet. However, most of the microorganisms are inaccessible in nature and are not easily cultivated in the laboratory. Metagenomic approaches provide a powerful tool to isolate and identify enzymes with novel biocatalytic activities for various biotechnological applications.</p> <p>Results</p> <p>A plasmid metagenomic library was constructed from uncultivated marine microorganisms within marine water samples. Through sequence-based screening of the DNA library, a gene encoding a novel fumarase (named FumF) was isolated. Amino acid sequence analysis revealed that the FumF protein shared the greatest homology with Class II fumarate hydratases from <it>Bacteroides </it>sp. 2_1_33B and <it>Parabacteroides distasonis </it>ATCC 8503 (26% identical and 43% similar). The putative fumarase gene was subcloned into pETBlue-2 vector and expressed in <it>E. coli </it>BL21(DE3)pLysS. The recombinant protein was purified to homogeneity. Functional characterization by high performance liquid chromatography confirmed that the recombinant FumF protein catalyzed the hydration of fumarate to form <smcaps>L</smcaps>-malate. The maximum activity for FumF protein occurred at pH 8.5 and 55°C in 5 mM Mg<sup>2+</sup>. The enzyme showed higher affinity and catalytic efficiency under optimal reaction conditions: <it>K</it><sub>m</sub>= 0.48 mM, <it>V</it><sub>max </sub>= 827 μM/min/mg, and <it>k</it><sub>cat</sub>/<it>K</it><sub>m </sub>= 1900 mM/s.</p> <p>Conclusions</p> <p>We isolated a novel fumarase gene, <it>fumF</it>, from a sequence-based screen of a plasmid metagenomic library from uncultivated marine microorganisms. The properties of FumF protein may be ideal for the industrial production of <smcaps>L</smcaps>-malate under higher temperature conditions. The identification of FumF underscores the potential of marine metagenome screening for novel biomolecules.</p
Low-mass dark matter search results from full exposure of PandaX-I experiment
We report the results of a weakly-interacting massive particle (WIMP) dark
matter search using the full 80.1\;live-day exposure of the first stage of the
PandaX experiment (PandaX-I) located in the China Jin-Ping Underground
Laboratory. The PandaX-I detector has been optimized for detecting low-mass
WIMPs, achieving a photon detection efficiency of 9.6\%. With a fiducial liquid
xenon target mass of 54.0\,kg, no significant excess event were found above the
expected background. A profile likelihood analysis confirms our earlier finding
that the PandaX-I data disfavor all positive low-mass WIMP signals reported in
the literature under standard assumptions. A stringent bound on the low mass
WIMP is set at WIMP mass below 10\,GeV/c, demonstrating that liquid xenon
detectors can be competitive for low-mass WIMP searches.Comment: v3 as accepted by PRD. Minor update in the text in response to
referee comments. Separating Fig. 11(a) and (b) into Fig. 11 and Fig. 12.
Legend tweak in Fig. 9(b) and 9(c) as suggested by referee, as well as a
missing legend for CRESST-II legend in Fig. 12 (now Fig. 13). Same version as
submitted to PR
iTRAQ-based proteomics profiling of Schwann cells before and after peripheral nerve injury
Objective(s): Schwann cells (SCs) have a wide range of applications as seed cells in the treatment of nerve injury during transplantation. However, there has been no report yet on kinds of proteomics changes that occur in Schwann cells before and after peripheral nerve injury.Materials and Methods: Activated Schwann cells (ASCs) and normal Schwann cells (NSCs) were obtained from adult Wistar rat sciatic nerves. After immunofluorescence identification, we identified differentially expressed proteins in the ASCs and NSCs using isobaric tags for relative and absolute quantitation (iTRAQ) combined with high-resolution Orbitrap liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). In addition, all the differentially expressed proteins were analyzed by Gene ontology (GO) analysis and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis. Finally, several differentially expressed proteins were selected for Western blot verification.Results: A total of 122 differentially expressed proteins in ASCs and NSCs were screened. GO analysis suggested that these different proteins are likely to accumulate in the cytoplasm and are associated with single-multicellular organism processes. The KEGG pathway analysis suggested that proteins related to purine metabolism were significantly enriched. The expression of Transmembrane glycoprotein NMB (GPNMB), Ectonucleotide pyrophosphatase/phosphodiesterase family member 3 (ENPP3), and other proteins were consistent with the proteomics data obtained by Western blot analysis. Conclusion: GPNMB, ENPP3, GFPT2, and other proteins may play an important role in the repair of peripheral nerve injury. This study may provide new insights into changes in SCs after peripheral nerve injury
A simulation study on the measurement of D0-D0bar mixing parameter y at BES-III
We established a method on measuring the \dzdzb mixing parameter for
BESIII experiment at the BEPCII collider. In this method, the doubly
tagged events, with one decays to
CP-eigenstates and the other decays semileptonically, are used to
reconstruct the signals. Since this analysis requires good separation,
a likelihood approach, which combines the , time of flight and the
electromagnetic shower detectors information, is used for particle
identification. We estimate the sensitivity of the measurement of to be
0.007 based on a fully simulated MC sample.Comment: 6 pages, 7 figure
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