Significant Enhanced SO2 Resistance of Pt/SiO2 Catalysts by Building the Ultrathin Metal Oxide Shell for Benzene Catalytic Combustion.

A noble metal catalyst shows excellent low-temperature oxidation activity in the catalytic combustion of benzene but has the problem of SO2 poisoning. We all know that SO2 easily competes with the reactant molecules for adsorption of the active site and has electronic effects on the active site to deactivate the catalyst. Therefore, the sulfur resistance of catalysts is the key problem to be solved in the process of catalytic combustion of benzene. Herein, the Pt/SiO2 catalyst with an ordered mesoporous structure was prepared by a one-step hydrothermal method, and MgO, ZnO, and MnOx were, respectively, coated on the surface of Pt/SiO2 as ultrathin shells to improve the sulfur resistance of Pt/SiO2. We observed that the sulfur resistance of the Pt/SiO2 catalyst was significantly improved due to the protective effect of the metal oxide shell. By comparing the three core-shell catalysts, it was found that the Pt/SiO2@MnOx catalyst coated with a MnOx shell had the best performance. The reason was that the MnOx shell not only protected the Pt active site but also had a good electron transfer effect on the core Pt, so it could effectively avoid the rapid adsorption poisoning of SO2 on the active Pt0 site. In addition, it was verified that the excellent redispersion of MnOx species in a SO2 atmosphere could increase the low-temperature oxidation activity of the Pt/SiO2@MnOx catalyst. Meanwhile, in situ DRIFT results also confirmed that the MnOx shell could significantly promote the oxidation of benzene molecules in the SO2 atmosphere.

Relationship between DHX15 expression and survival in colorectal cancer.

OBJECTIVE: to explore the relationship between the expression of DEAH-box RNA helicase 15 (DHX15) in colorectal cancer (CRC), its clinical pathological features and survival. METHOD: DHX15 expression data with clinical pathological features from the Cancer Gene Atlas (TCGA) and the Clinical Proteomic Tumor Analysis Consortium (CPTAC) were statistically analyzed for the association between DHX15 expression and overall survival in CRC. The expression of DHX15 was performed by immunohistochemical staining (IHC) using tumor and the adjacent normal tissue, mounted in tissue microarrays. The significance of DHX15 expression to predict survival and prognosis of CRC were analyzed using the Kaplan-Meier method, univariate and multivariate Cox regression analysis. RESULTS: low expression of DHX15 mRNA and DHX15 protein in CRC were both negative factors for survival. Overall survival of patients with low-expression of DHX15 was significantly lower (χ2 = 8.452, p = 0.004) by Kaplan-Meier evaluation. Low expression of DHX15 in CRC tissues correlated with distal lymph node metastasis (χ² = 7.120, p = 0.008), TNM stage (χ² = 3.935, p = 0.047) and disease recurrence (χ² = 9.524, p = 0.002) in CRC. Low expression of DHX15 (HR = 4.012, 95 % CI: 1.462-11.013, p = 0.007), late TNM stage (HR = 0.067, 95 % CI: 0.029-0.156, p < 0.001) and recurrence (HR = 0.008, 95 % CI: 0.002-0.034, p < 0.001) were risk factors related to the prognosis of CRC patients by univariate Cox regression analysis. CONCLUSION: our findings reveal a key role for DHX15 in the progress of CRC metastasis and recurrence. DHX15 may be a potential biomarker for CRC targeted therapy.

Genomic mechanisms of climate adaptation in polyploid bioenergy switchgrass.

Long-term climate change and periodic environmental extremes threaten food and fuel security1 and global crop productivity2-4. Although molecular and adaptive breeding strategies can buffer the effects of climatic stress and improve crop resilience5, these approaches require sufficient knowledge of the genes that underlie productivity and adaptation6-knowledge that has been limited to a small number of well-studied model systems. Here we present the assembly and annotation of the large and complex genome of the polyploid bioenergy crop switchgrass (Panicum virgatum). Analysis of biomass and survival among 732 resequenced genotypes, which were grown across 10 common gardens that span 1,800 km of latitude, jointly revealed extensive genomic evidence of climate adaptation. Climate-gene-biomass associations were abundant but varied considerably among deeply diverged gene pools. Furthermore, we found that gene flow accelerated climate adaptation during the postglacial colonization of northern habitats through introgression of alleles from a pre-adapted northern gene pool. The polyploid nature of switchgrass also enhanced adaptive potential through the fractionation of gene function, as there was an increased level of heritable genetic diversity on the nondominant subgenome. In addition to investigating patterns of climate adaptation, the genome resources and gene-trait associations developed here provide breeders with the necessary tools to increase switchgrass yield for the sustainable production of bioenergy.

Expression and protease characterization of a conserved protein YgjD in Vibrio harveyi.

The glycopeptidase GCP and its homologue proteins are conserved and essential for survival of bacteria. The ygjD gene (Glycopeptidase homologue) was cloned from Vibrio harveyi strain SF-1. The gene consisted of 1,017 bp, which encodes a 338 amino acid polypeptide. The nucleotide sequence similarity of the ygjD gene with that of V. harveyi FDAARGOS 107 was 95%. The ygjD gene also showed similarities of 68%, 67% and 50% with those of Salmonella enterica, Escherichia coli and Bacillus cereus. The ygjD gene was expressed in E. coli BL21 (DE3) and the recombinant YgjD was purified by Ni2+ affinity chromatography column. The purified YgjD showed a specific 37 kDa band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and exhibited protease activities of 59,000 units/mg, 53,700 units/mg and 8,100 units/mg, respectively, on N-Acetyl-L-tyrosine ethyl ester monohydrate (ATEE), N-Benzoyl-L-tyrosine ethyl ester (BTEE) and N-Benzoyl-DL-arginine-4-nitroanilide hydrochloride (BAPNA) substrates. When the conserved amino acids of His111, Glu113 and His115 in the YgjD were replaced with alanine, respectively, the protease activities of the mutants were partly decreased. The two conserved His111 and His115 of YgjD were mutated and the protein lost the protease activity, which implied that the two amino acid played very important roles in maintaining its protease activity. The addition of the purified YgjD to the culture medium of V. harveyi strain SF-1 can effectively promote the bacteria growth. These results indicated that the protease activities may be involved in the survival of bacteria.

Downregulation of a UDP-Arabinomutase Gene in Switchgrass (Panicum virgatum L.) Results in Increased Cell Wall Lignin While Reducing Arabinose-Glycans.

Background: Switchgrass (Panicum virgatum L.) is a C4 perennial prairie grass and a dedicated feedstock for lignocellulosic biofuels. Saccharification and biofuel yields are inhibited by the plant cell wall's natural recalcitrance against enzymatic degradation. Plant hemicellulose polysaccharides such as arabinoxylans structurally support and cross-link other cell wall polymers. Grasses predominately have Type II cell walls that are abundant in arabinoxylan, which comprise nearly 25% of aboveground biomass. A primary component of arabinoxylan synthesis is uridine diphosphate (UDP) linked to arabinofuranose (Araf). A family of UDP-arabinopyranose mutase (UAM)/reversible glycosylated polypeptides catalyze the interconversion between UDP-arabinopyranose (UDP-Arap) and UDP-Araf. Results: The expression of a switchgrass arabinoxylan biosynthesis pathway gene, PvUAM1, was decreased via RNAi to investigate its role in cell wall recalcitrance in the feedstock. PvUAM1 encodes a switchgrass homolog of UDP-arabinose mutase, which converts UDP-Arap to UDP-Araf. Southern blot analysis revealed each transgenic line contained between one to at least seven T-DNA insertions, resulting in some cases, a 95% reduction of native PvUAM1 transcript in stem internodes. Transgenic plants had increased pigmentation in vascular tissues at nodes, but were otherwise similar in morphology to the non-transgenic control. Cell wall-associated arabinose was decreased in leaves and stems by over 50%, but there was an increase in cellulose. In addition, there was a commensurate change in arabinose side chain extension. Cell wall lignin composition was altered with a concurrent increase in lignin content and transcript abundance of lignin biosynthetic genes in mature tillers. Enzymatic saccharification efficiency was unchanged in the transgenic plants relative to the control. Conclusion: Plants with attenuated PvUAM1 transcript had increased cellulose and lignin in cell walls. A decrease in cell wall-associated arabinose was expected, which was likely caused by fewer Araf residues in the arabinoxylan. The decrease in arabinoxylan may cause a compensation response to maintain cell wall integrity by increasing cellulose and lignin biosynthesis. In cases in which increased lignin is desired, e.g., feedstocks for carbon fiber production, downregulated UAM1 coupled with altered expression of other arabinoxylan biosynthesis genes might result in even higher production of lignin in biomass.

Overexpression of AtLOV1 in Switchgrass alters plant architecture, lignin content, and flowering time.

BACKGROUND: Switchgrass (Panicum virgatum L.) is a prime candidate crop for biofuel feedstock production in the United States. As it is a self-incompatible polyploid perennial species, breeding elite and stable switchgrass cultivars with traditional breeding methods is very challenging. Translational genomics may contribute significantly to the genetic improvement of switchgrass, especially for the incorporation of elite traits that are absent in natural switchgrass populations. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we constitutively expressed an Arabidopsis NAC transcriptional factor gene, LONG VEGETATIVE PHASE ONE (AtLOV1), in switchgrass. Overexpression of AtLOV1 in switchgrass caused the plants to have a smaller leaf angle by changing the morphology and organization of epidermal cells in the leaf collar region. Also, overexpression of AtLOV1 altered the lignin content and the monolignol composition of cell walls, and caused delayed flowering time. Global gene-expression analysis of the transgenic plants revealed an array of responding genes with predicted functions in plant development, cell wall biosynthesis, and flowering. CONCLUSIONS/SIGNIFICANCE: To our knowledge, this is the first report of a single ectopically expressed transcription factor altering the leaf angle, cell wall composition, and flowering time of switchgrass, therefore demonstrating the potential advantage of translational genomics for the genetic improvement of this crop.