Potential biofuel additive from renewable sources--Kinetic study of formation of butyl acetate by heterogeneously catalyzed transesterification of ethyl acetate with butanol

Butyl acetate holds great potential as a sustainable biofuel additive. Heterogeneously catalyzed transesterification of biobutanol and bioethylacetate can produce butyl acetate. This route is eco-friendly and offers several advantages over the commonly used Fischer Esterification. The Amberlite IR 120- and Amberlyst 15-catalyzed transesterification is studied in a batch reactor over a range of catalyst loading (6–12 wt.%), alcohol to ester feed ratio (1:3 to 3:1), and temperature (303.15–333.15 K). A butanol mole fraction of 0.2 in the feed is found to be optimum. Amberlite IR 120 promotes faster kinetics under these conditions. The transesterifications studied are slightly exothermic. The moles of solvent sorbed per gram of catalyst decreases (ethanol > butanol > ethyl acetate > butyl acetate) with decrease in solubility parameter. The dual site models, the Langmuir Hinshelwood and Popken models, are the most successful in correlating the kinetics over Amberlite IR 120 and Amberlyst 15, respectively.     

Oxidative stress and the etiology of insulin resistance and type 2 diabetes

The condition of oxidative stress arises when oxidant production exceeds antioxidant activity in cells and plasma. The overabundance of oxidants is mechanistically connected to the multifactorial etiology of insulin resistance, primarily in skeletal muscle tissue, and the subsequent development of type 2 diabetes. Two important mechanisms for this oxidant excess are (1) the mitochondrial overproduction of hydrogen peroxide and superoxide ion under conditions of energy surplus and (2) the enhanced activation of cellular NADPH oxidase via angiotensin II receptors. Several recent studies are reviewed that support the concept that direct exposure of mammalian skeletal muscle to an oxidant stress (including hydrogen peroxide) results in stimulation of the serine kinase p38 mitogen-activated protein kinase (p38 MAPK), and that the engagement of this stress-activated p38 MAPK signaling is mechanistically associated with diminished insulin-dependent stimulation of insulin signaling elements and glucose transport activity. The beneficial interactions between the antioxidant α-lipoic acid and the advanced glycation end-product inhibitor pyridoxamine that ameliorate oxidant stress-associated defects in whole-body and skeletal-muscle insulin action in the obese Zucker rat, a model of prediabetes, are also addressed. Overall, this review highlights the importance of oxidative stress in the development of insulin resistance in mammalian skeletal muscle tissue, at least in part via a p38-MAPK-dependent mechanism, and indicates that interventions that reduce this oxidative stress and oxidative damage can improve insulin action in insulin-resistant animal models. Strategies to prevent and ameliorate oxidative stress remain important in the overall treatment of insulin resistance and type 2 diabetes.     

原油微生物群落构成多样性及降解菌DYL-1降解原油的研究

为分离得到高效原油降解菌,直接向原油中加入营养物刺激,培养一段时间后原油乳化降解,傅里叶红外光谱显示,2957cm-1、723cm-1处吸收峰消失;2855cm-1、1377cm-1处吸收峰减弱;880cm-1以及800cm-1吸收峰几乎消失,表明原油发生降解,效果明显。同时分离得到一株降解菌,经分子鉴定为芽孢杆菌属(Bacillus sp.),红外光谱法和紫外吸收法分析表明其具有较强的降解原油烃的能力。根据传统分子生物学的方法,构建原油菌16S rDNA克隆文库,限制性酶切片段长度多态性(Restriction Fragment Length Polymorphism,RFLP)分析了原油中的细菌多样性。结果表明此方法有效地评估了原油中的细菌群落和多样性。     

The effects of K+ growth conditions on the accumulation of cesium by the bacterium Thermus sp. TibetanG6

The accumulation of cesium by the bacterium Thermus sp. TibetanG6 was examined under different K⁺ growth conditions. The effects of external pH and Na⁺ on the accumulation of cesium were also studied, and the mechanism involved was discussed. K⁺ regimes played an important role in the accumulation of cesium by the strain TibetanG6. The quantity of cesium accumulated (24 h) was much higher in K⁺-deficient regime than that in K⁺-sufficient regime. The pH and Na⁺ had different effects on the accumulation of cesium in the two K⁺ regimes. IR spectra analyses indicated that the biosorption is a process of homeostasis with cesium initially accumulated on the cell wall.     

Mapping of nutrient-induced biochemical changes in living algal cells using synchrotron infrared microspectroscopy

High quality Fourier transform infrared (FTIR) spectra were acquired from living Micrasterias hardyi cells maintained in an IR transparent flow-through cell using a FTIR microscope coupled to a synchrotron light source. Spectral maps of living, nutrient-replete cells showed band intensities consistent with the known location of the nucleus and the chloroplasts. These were very similar to maps acquired from fixed, air-dried cells. Bands due to lipids were lowest in absorbance in the region of the nucleus and highest in the chloroplast region and this trend was reversed for the absorbance of bands attributed to protein. Spectra acquired in 10 microm steps across living phosphorus-starved (P-starved) cells, repeated approximately every 30 min, were consistent over time, and bands correlated well with the known position of the nucleus and the observed chloroplasts, corroborating the observations with replete cells. Experiments in which missing nutrients were re-supplied to starved cells showed that cells could be maintained in a functional state in the flow-through cell for up to one day. Nitrogen-starved cells re-supplied with N showed an increase in lipid in all positions measured across the cell over a 23 h period of re-supply, with the largest increases occurring in positions where the chloroplasts were observed. Re-supply of phosphorus to P-starved cells produced no changes in bands attributable to lipid or protein. Due to their thin cell body ( approximately 12 microm) and large diameter ( approximately 300 microm) Micrasterias sp. make an ideal spectroscopic model to study nutrient kinetics in algal cells.     

The effect of temperature on DNA structural transitions under the action of Cu2+ and Ca2+ ions in aqueous solutions

The work examines the structural transitions of DNA under the action of Cu2+ and Ca2+ ions in aqueous solution at temperatures of 29 and 45 degrees C by ir spectroscopy. Upon binding to the divalent ions studied, DNA transits into the compact state both at 29 and 45 degrees C. In the compact state DNA remains in B-form limits. The compaction process is of high positive cooperativity. As temperature increases the divalent metal ion concentration required to induce DNA compaction decreases in the case of Cu(2+)-induced compaction and increases in the case of Ca(2+)-induced compaction. It is suggested that the mechanism of the temperature effect on DNA compaction in the presence of Cu2+ ions possessing higher affinity for DNA bases differs from that of the temperature influence on Ca(2+)-induced DNA compaction. In the case of copper ions the determining factor is the increase of binding constants of the Cu2+ ions interacting with the denatured parts formed on DNA while in the case of calcium ions it is the decreased screening action of counterions upon the increase of their hydration with temperature. The efficiency of divalent metal ions studied in inducing DNA compaction depends on hydration of counterions. DNA compaction occurs in a narrow interval of Cu2+ concentrations. As the Cu2+ ion concentration increases, DNA compaction is replaced with Cu(2+)-induced DNA aggregation. At elevated temperatures Cu(2+)-induced DNA compaction could acquire a phase transition character.     

Knock-down of LAR protein tyrosine phosphatase induces insulin resistance

To test the role of the leukocyte common antigen-related protein tyrosine phosphatase (LAR) as a regulator of insulin receptor (IR) signalling, an siRNA probe against LAR was developed. Knock-down of LAR induced post-receptor insulin resistance with the insulin-induced activation of PKB/Akt and MAP kinases markedly inhibited. The phosphorylation and dephosphorylation of the IR and insulin receptor substrate (IRS) proteins were unaffected by LAR knock-down. These results identify LAR as a crucial regulator of the sensitivity of two key insulin signalling pathways to insulin. Moreover, the siRNA probe provides a molecular tool of general applicability for further dissecting the precise targets and roles of LAR.     

Fourier transform infared spectroscopy investigation of protein conformation in spray-dried protein/trehalose powders

Spray drying is a way to generate protein solids (powders), which is also true for lyophilization. Sugars are used to protect proteins from conformational changes and chemical degradations arising from drying processes and storage conditions such as the humidity. The influence of trehalose and humidity on the conformation and hydration of spray-dried recombinant human granolucyte colony stimulating factor (rhG-CSF) and recombinant consensus interferon-alpha (rConIFN) was investigated using Fourier transform IR spectroscopy. The spectral analysis of spray-dried powders in the amide I region demonstrated that trehalose stabilized the alpha-helical conformation of both rhG-CSF and rConIFN proteins. Exposure of the pure protein powders to 33% relative humidity (RH) resulted in the formation of beta sheets and loss of turns but no change in alpha-helical structure. Trehalose reduced the magnitude of the changes in beta sheets and turns. Exposure of the pure protein powders to 75% RH resulted in the loss of alpha-helical conformation with a corresponding increase in beta structures (beta sheets and turns). Trehalose did not protect proteins from the loss of alpha-helical structures, but it reduced the formation of antiparallel beta sheets. Hydrogen-deuterium exchange (H-D exchange) was used to further characterize these hydration-induced conformational changes. At 33% RH the percent exchange of the protein decreased with increasing trehalose content, indicating a greater protection of the protein from H-D exchange by a higher concentration of trehalose. Such protection correlates with decreased conformational changes of the protein by trehalose at this humidity. At 75% RH the degree of H-D exchange of the protein was insensitive to the powder composition in all powders. Surprisingly, the H-D exchange of trehalose was low at about 20-25%, which was nearly independent of the protein/trehalose ratio and humidity, indicating that the exchangeable protons on trehalose molecules are highly protected in protein-containing powders. The observed protein hydration is related to the effect of trehalose on the conformational changes of the protein under humidity.     

IR-inducible clusterin gene expression: a protein with potential roles in ionizing radiation-induced adaptive responses, genomic instability, and bystander effects

Clusterin (CLU) plays numerous roles in mammalian cells after stress. A review of the recent literature strongly suggests potential roles for CLU proteins in low dose ionizing radiation (IR)-inducible adaptive responses, bystander effects, and delayed death and genomic instability. Its most striking and evident feature is the inducibility of the CLU promoter after low, as well as high, doses of IR. Two major forms of CLU, secreted (sCLU) and nuclear (nCLU), possess opposite functions in cellular responses to IR: sCLU is cytoprotective, whereas nCLU (a byproduct of alternative splicing) is a pro-death factor. Recent studies from our laboratory and others demonstrated that down-regulation of sCLU by specific siRNA increased cytotoxic responses to chemotherapy and IR. sCLU was induced after low non-toxic doses of IR (0.02-0.5 Gy) in human cultured cells and in mice in vivo. The low dose inducibility of this survival protein suggests a possible role for sCLU in radiation adaptive responses, characterized by increased cell radioresistance after exposure to low adapting IR doses. Although it is still unclear whether the adaptive response is beneficial or not to cells, survival of damaged cells after IR may lead to genomic instability in the descendants of surviving cells. Recent studies indicate a link between sCLU accumulation and cancer incidence, as well as aging, supporting involvement of the protein in the development of genomic instability. Secreted after IR, sCLU may also alter intracellular communication due to its ability to bind cell surface receptors, such as the TGF-beta receptors (types I and II). This interference with signaling pathways may contribute to IR-induced bystander effects. We hypothesize that activation of the TGF-beta signaling pathway, which often occurs after IR exposure, can in turn activate the CLU promoter. TGF-beta and IR-inducible de novo synthesized sCLU may then bind the TGF-beta receptors and suppress downstream growth arrest signaling. This complicated negative feedback regulation most certainly depends on the cellular microenvironment, but undoubtedly represents a potential link between IR-induced adaptive responses, genomic instability and bystander effects. Further elucidation of clusterin protein functions in IR responses are clearly warranted.     

All-Atom Structural Models for Complexes of Insulin-Like Growth Factors IGF1 and IGF2 with Their Cognate Receptor

Type 1 insulin-like growth factor receptor (IGF1R) is a membrane-spanning glycoprotein of the insulin receptor family that has been implicated in a variety of cancers. The key questions related to molecular mechanisms governing ligand recognition by IGF1R remain unanswered, partly due to the lack of testable structural models of apo or ligand-bound receptor complexes. Using a homology model of the IGF1R ectodomain IGF1RΔβ, we present the first experimentally consistent all-atom structural models of IGF1/IGF1RΔβ and IGF2/IGF1RΔβ complexes. Our explicit-solvent molecular dynamics (MD) simulation of apo-IGF1RΔβ shows that it displays asymmetric flexibility mechanisms that result in one of two binding pockets accessible to growth factors IGF1 and IGF2, as demonstrated via an MD-assisted Monte Carlo docking procedure. Our MD-generated ensemble of structures of apo and IGF1-bound IGF1RΔβ agrees reasonably well with published small-angle X-ray scattering data. We observe simultaneous contacts of each growth factor with sites 1 and 2 of IGF1R, suggesting cross-linking of receptor subunits. Our models provide direct evidence in favor of suggested electrostatic complementarity between the C-domain (IGF1) and the cysteine-rich domain (IGF1R). Our IGF1/IGF1RΔβ model provides structural bases for the observation that a single IGF1 molecule binds to IGF1RΔβ at low concentrations in small-angle X-ray scattering studies. We also suggest new possible structural bases for differences in the affinities of insulin, IGF1, and IGF2 for their noncognate receptors.