Most oil producing countries have extensive reserves of heavy oil and bitumen. As easily accessible sources of conventional crudes decline, these reserves will become more important in supplementing the energy requirements. Heavy oil and bitumen are highly viscous and contain 3 to 6% sulphur. These objectionable quantities of sulphur must be removed before being acceptable as refinery feedstock. This paper addresses the potential of biological desulphurization of heavy oil and bitumen. The aerobic and anaerobic processes to remove organic as well as inorganic sulphur have been reviewed. To date, most studies were performed with model substrates, particularly dibenzothiophene (DBT) in a synthetic medium. Early work concerned with the isolation of microorganisms, identification and characterization of intermediate metabolites, and the development of growth media. No commercially viable process has emerged since the engineering details of the process have not been addressed conclusively. Due to high utility and catalyst cost conventional hydrodesulphurization processes are reported to be uneconomic in case of high sulphur oils. Microbial desulphurization, on the other hand, appears to be promising due to the inherent low energy requirement. This process may become more attractive by the application of genetically modified bacteria and improvements in bioreactor design. 相似文献
L-Epinephrine, serotonin, and isoproterenol stimulate the incorporation of [14C]leucine into thrombin-induced clottable protein; this stimulation was abolished by actinomycin D. The incorporation of 32P into total RNA of rat liver, the site of fibrinogen synthesis, was stimulated by epinephrine and was highest at 2 h after 32P administration. [14C]Orotic acid incorporation into polysomal RNA of liver was also increased significantly by epinephrine and serotonin. The immunoprecipitation of newly synthesized protein by monospecific antibody raised against pure rat fibrinogen clearly demonstrates that L-epinephrine increased fibrinogen formation in vivo under the experimental condition. Translation of poly (A)-containing RNA from total polysomal RNA clearly indicates that L-epinephrine increased mRNA specific for fibrinogen. 相似文献
A non-equilibrium thermodynamic theory of generalized Lotka-Volterra ecosystem has been presented. The main results consist of the derivation of a generalized expression of entropy-production for the evolutionary ecosystem and the study of its role in the analysis of ecological stability, succession and also in the formulation of some extremum principles characterising the evolution of the ecosystem. 相似文献
Silica gel TLC methods were developed for the separation of 2,4,6-trinitrotoluene (TNT) in mixtures with possible reduction products. The methods employed repeated elutions with simple binary or ternary solvent systems in either one or two dimensional modes. The resolved analytes include TNT, selected amino derivatives (2-amino-4,6-di-nitrotoluene, 4-amino-2,6-dinitrotoluene, 2,4-diamino-6-nitrotoluene) and known hydroxylamino derivatives (2-hydroxyl-amino-4,6-dinitrotoluene, 4-hydroxylamino-2,6-dinitrotoluene and 2,4-dihydroxylamino-6-nitrotoluene). 相似文献
A collection of 521 environmental isolates of Vibrio cholerae which were previously examined by the suckling mouse assay and found to be negative for the heat-stable enterotoxin NAG-ST were reassessed by a recently developed DNA probe for NAG-ST. A total of 12 (2.3%) of the isolates hybridized with the NAG-ST probe. By using a cholera toxin (CT) DNA probe, the CT gene was detected in six of the strains in the collection, although none of the isolates of V. cholerae non-O1 hybridized with both of the toxin probes. All of the NAG-ST and CT probe-positive strains were hemolysin positive. Thirty-fold-concentrated supernatants of the three representative NAG-ST DNA probe-positive V. cholerae non-O1 strains gave positive fluid accumulation ratios in the suckling mouse assay even after heating (100 degrees C for 5 min) and also inhibited the binding of a NAG-ST monoclonal antibody to the bound NAG-ST in a competitive enzyme-linked immunosorbent assay (ELISA). Likewise, all six CT probe-positive V. cholerae non-O1 strains produced in vitro CT when examined by the CT bead ELISA. HindIII digest patterns of chromosomal DNA from the representative NAG-ST gene-positive strains were visually indistinguishable. Between the groups of NAG-ST probe-positive strains examined, there was a variation in the hybridizable fragments, with one group of strains exhibiting a hybridizable fragment similar to that of the NRT 36 reference strain; a smaller HindIII fragment hybridized with the NAG-ST probe in the other group of strains.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
Recent studies from this laboratory have shown that fetuin 1) is nearly 50-fold more efficient than albumin in incorporating exogenous fatty acids into cultured cells, (JBC, 265: 5883, 1990), and 2) is associated with a lipoprotein-like particle (FASEB J. 3: 2075-2080, 1989). In the present study, this lipid-containing fraction (FLP) was isolated by ultracentrifugation, and its effect on cholesterol efflux from cultured human skin fibroblasts and Hep-G2 cells prelabeled with [14C]cholesterol was investigated. FLP fraction caused a significant efflux of [14C]cholesterol from cells, the same in magnitude as HDL. This effect of fetuin supranatant fraction increased proportionately with concentration and time. Similar results were observed with Hep-G2 cells. This ability to induce efflux of cholesterol was confirmed by a decrease in cholesterol mass of cells after 24 h incubation with FLP. The ultracentrifugal bottom (infranatant) fraction of fetuin (FI) was ineffective in this regard. However, FI was more effective in the incorporation of exogenous fatty acids into cellular triglycerides. These studies suggest that the fetuin molecule is a multifunctional protein (delivery of fatty acids to cells and cholesterol efflux from cells) which may play a role in lipid transport during fetal life. 相似文献
The present study intends to evaluate the role of radio-attenuated leishmania parasites as immunoprophylactic agents for experimental murine visceral leishmaniasis. BALB/c mice were immunized with gamma (γ)-irradiated Leishmania donovani. A second immunization was given after 15 days of first immunization. After two immunizations, mice were infected with virulent L. donovani promastigotes. Protection against Kala-azar (KA) was estimated from spleen and liver parasitic burden along with the measurement of nitrite and superoxide anion generation by isolation of splenocytes and also by T-lymphocyte helper 1(Th1) and T-lymphocyte helper 2(Th2) cytokines release from the experimental groups. It was observed that BALB/c mice having prior immunization with radio-attenuated parasites showed protection against L. donovani infection through higher expression of Th1 cytokines and suppression of Th2 cytokines along with the generation of protective free radicals. The group of mice without prior priming with radio-attenuated parasites surrendered to the disease. Thus it can be concluded that radio-attenuated L. donovani may be used for. 相似文献
Cisplatin has been extensively used in therapeutics for its broad-spectrum anticancer activity and frequently used for the treatment of solid tumors. However, it presents several side-effects and several cancers develop resistance. Combination therapy of cisplatin with poly (ADP-ribose) polymerase 1 (PARP1) inhibitors has been effective in increasing its efficacy at lower doses.
Methods and results
In this work, we have shown that the nitro-flavone derivative, 2-(4-Nitrophenyl)-4H-chromen-4-one (4NCO), can improve the sensitivity of cancer cells to cisplatin through inhibition of PARP1. The effect of 4NCO on cisplatin toxicity was studied through combination therapy in both exponential and density inhibited A375 melanoma cells. Combination index (CI) was determined from isobologram analysis. The mechanism of cell killing was assessed by lactate dehydrogenase (LDH) assay. Temporal nicotinamide adenine dinucleotide (NAD+) assay was done to show the inhibition of PARP1. We also performed in silico molecular modeling studies to know the binding mode of 4NCO to a modeled PARP1-DNA complex containing cisplatin-crosslinked adduct. The results from both in silico and in cellulo studies confirmed that PARP1 inhibition by 4NCO was most effective in sensitizing A375 melanoma cells to cisplatin. Isobologram analysis revealed that 4NCO reduced cell viability both in exponential and density inhibited A375 cells synergistically. The combination led to cell death through apoptosis.
Conclusion
The synthetic nitro-flavone derivative 4NCO effectively inhibited the important nuclear DNA repair enzyme PARP1 and therefore, could complement the DNA-damaging anticancer drug cisplatin in A375 cells and thus, could act as a potential adjuvant to cisplatin in melanoma therapy.
The Sec complex catalyzes the translocation of proteins of the secretory pathway into the endoplasmic reticulum and the integration of membrane proteins into the endoplasmic reticulum membrane. Some substrate peptides require the presence and involvement of accessory proteins such as Sec63. Recently, a structure of the Sec complex from Saccharomyces cerevisiae, consisting of the Sec61 channel and the Sec62, Sec63, Sec71 and Sec72 proteins was determined by cryo-electron microscopy (cryo-EM). Here, we show by co-precipitation that the Sec61 channel subunit Sbh1 is not required for formation of stable Sec63-Sec61 contacts. Molecular dynamics simulations started from the cryo-EM conformation of Sec61 bound to Sec63 and of unbound Sec61 revealed how Sec63 affects the conformation of Sec61 lateral gate, plug, pore region and pore ring diameter via three intermolecular contact regions. Molecular docking of SRP-dependent vs. SRP-independent signal peptide chains into the Sec61 channel showed that the pore regions affected by presence/absence of Sec63 play a crucial role in positioning the signal anchors of SRP-dependent substrates nearby the lateral gate. 相似文献