Evaluation on hydrothermal gasification of styrene-butadiene rubber with oxidants via ReaxFF-MD simulation.

Styrene-butadiene rubber (SBR) is widely used in tires, which brings great challenge to the disposal and reclaiming of the used tires. The ring-opening reaction pathways of benzene rings in hydrothermal gasification of styrene-butadiene rubber were revealed based on reactive force field molecular dynamics (ReaxFF-MD) simulation. H-abstraction reaction that OH radicals capture H atom from the vinyl group of styrene was critical to the degrading of the styrene monomers. The energy barrier of H2O2 converted to OH radicals was lower than that of O2 and pure water converted to OH radicals. The oxidants that can urge OH radical formed in reaction were beneficial to SBR degradation, which could be assigned to confirm that SBR degradation with H2O2 was better than that with oxygen at the same concentration. The addition of oxidant could be helpful for decreasing the degradation temperature of styrene monomers. At oxidant equivalent ratio (ER) of 0.1, H2 yield at 2500 K lifted after 135 ps and increased by 75% at 500 ps compared with that without oxidants. According to the chemical equilibrium analysis, the optimal ER for H2 was 0.4 between 350 and 600 °C (real temperatures). The results could provide theoretic support and experiment guidance for adding oxidants in reclaiming waste rubber products.

Direct synthesis of heparin-like poly(ether sulfone) polymer and its blood compatibility.

In this study, heparin-like poly(ethersulfone) (HLPES) was synthesized by a combination of polycondensation and post-carboxylation methods, and was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum and gel permeation chromatography. Owing to the similar backbone structure, the synthesized HLPES could be directly blended with pristine PES at any ratios to prepare PES/HLPES membranes. After the introduction of HLPES, the microscopic structure of the modified PES membranes was changed, while the hydrophilicity was significantly enhanced. Bovine serum albumin and bovine serum fibrinogen adsorption, activated partial thromboplastin time, thromb time and platelet adhesion for the modified PES membranes were investigated. The results indicated that the blood compatibility of the PES/HLPES membranes was significantly improved compared with that of pristine PES membrane. For the PES/HLPES membranes, obvious decreases in platelet activation on PF-4 level, in complement activation on C3a and C5a levels, and in leukocytes activation on CD11b levels were observed compared with those for the pristine PES membrane. The improved blood compatibility of the PES/HLPES membrane might due to the existence of the hydrophilic groups (-SO3Na, -COONa). Furthermore, the modified PES membranes showed good cytocompatibility. Hepatocytes cultured on the PES/HLPES membranes presented improved growth in terms of SEM observation, MTT assay and confocal laser scanning microscope observation compared with those on the pristine PES membrane. These results indicate that the PES/HLPES membranes present great potential in blood-contact fields such as hemodialysis and bio-artificial liver supports.

[Research advances on fusion peptide and mechanisms about virus penetration into membrane].

The first step of viral infection is virus fusion with target membrane. The process is induced by fusion peptide located in glycoprotein on virus membrane. Fusion peptide exploited after interaction with receptors and penetrates into target cells membrane. Lipid molecules surrounding peptides are rearranged and membrane fusion occurs through the formation of a intermediate state. This review introduces the research advances of viral fusion peptides and its mechanism of penetrating into membrane.

[A comparative study on anti-ulcer action of unprepared and calcined oyster shell].

On experimental gastric ulcer models induced by 0.6mol/L HCl, ethyl alcohol or ligation of the pylorus, the preventive effects of unprepared oyster shell, calcined oyster shell 1(900 degrees C, 1h), calcined oyster shell 2(350 degrees C, 8h) were compared in Wistar rats. Results showed that antagonistic effects of calcined oyster shell 1 to the drug pathogenesis of peptic ulcer and the incidence of peptic ulcer after ligation of the pylorus were markedly greater.

Analogues of tetramethylpyrazine affect membrane fluidity of liposomes: relationship to their biological activities.

Several structurally similar pyrazine derivatives, tetramethylpyrazine, triethylpyrazine and tetraethylpyrazine have previously been found to inhibit a broad spectrum of plasmalemma-associated biological activities of various tissues, including ion channels and membrane receptors in a given order of potency that increases with increasing bulkiness and hydrophobicity of these drugs. Our earlier speculation that the multiple membrane effects elicited by these pyrazine derivatives were associated with changes in the bulk physical properties of the biological membranes in the presence of these drugs was confirmed by fluorescence polarization and electron spin resonance studies. Since biological membranes contain a complicated mixture of a large variety of lipids and proteins, we chose to study the molecular properties of the interaction of these three pyrazine derivatives using a simple model system composed of synthetic phospholipids. We measured the effects of the drugs on the fluidity (or microviscosity) of these model membranes, as well as determining the phase-transition properties of the model membranes with the use of fluorescence polarization, electron spin resonance and differential scanning calorimetry. All the methods employed yielded qualitatively similar results. Tetramethylpyrazine, the smallest and the least hydrophobic amongst these three drugs, had minimal or no effect on the phase-transition of phospholipids based on temperature dependence studies, whereas tetraethylpyrazine, the largest and the most hydrophobic of the three, elicited the most potent effect in a concentration-dependent manner. These results could be attributed to the amount of incorporation of these pyrazine derivative into the liposomes, an interaction which occurs more favourably at temperatures above the gel to liquid crystalline phase-transition temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Reciprocal effects of apolipoprotein and lytic peptide analogs on membranes. Cross-sectional molecular shapes of amphipathic alpha helixes control membrane stability.

Apolipoprotein (class A) amphipathic helixes are postulated to act as detergents by virtue of their cross-section being wedge-shaped. Using computer analysis of naturally occurring class A and lytic (class L) amphipathic helixes, we designed two archetypical model peptides. Analogs of these two peptides, incorporating substitutions or modifications of interfacial or basic residues, had the following effects. Class A peptides stabilized bilayer structure, reduced leakage from large unilamellar vesicles and erythrocytes, and inhibited lysis induced by class L peptides. Class L peptides destabilized bilayer structure in model membranes and increased binding of class A peptides to erythrocytes. The ability of class L analogs to lyse membranes and induce inverted lipid phases was reduced by either decreasing the bulk of an interfacial residue, increasing the angle subtended by the polar face, or increasing the bulk of the basic residues. The ability of the class A analog to stabilize bilayer structure and inhibit erythrocyte lysis by class L peptides was enhanced by methylating the Lys residues. These results can be explained by a model that we term the reciprocal wedge hypothesis. By analogy to the reciprocal effects of phospholipid shapes on membrane structure, we propose that the wedge shape of class A helixes stabilizes membrane bilayers, whereas the inverted wedge shape of class L helixes destabilizes membrane bilayers, and, thus, one class will neutralize the effect of the other class on membranes.

[Effects of processing on special toxicity and pharmacodynamics in semen Armeniacae amarum].

The ethereal extract and decoction from raw Semen Armeniacae Amarum were found to induce EBV-EA activation in Raji cells cultured in vitro. Experiments show that both the extract and decoction have tumor-promoting activities, but the EBV-EA activation can be decreased by three kinds of processing-parching, scalding or parching after scalding, of which parching and parching after scalding are better. Moreover, parching after scalding is the best to enhance the relaxing of bowels, inactivate the amygdalase and increase the decoction rate of amygdalin.

Pyrazine derivatives affect membrane fluidity of vascular smooth muscle microsomes in relation to their biological activity.

We have previously demonstrated that several structurally similar pyrazine derivatives, tetramethylpyrazine (TMP), triethylpyrazine (3EP) and tetraethylpyrazine (TEP) consistently inhibited a wide spectrum of plasmalemma-associated biological activities of vascular smooth muscles in contractility and radioligand binding studies in the following order of increasing potency, TMP < 3EP < TEP. We speculated that these pyrazine derivatives elicit multiple effects in the above order of potency by affecting, at least in part, the bulk physical properties of the lipid bilayers in the cell membrane. This hypothesis was tested in the current study using plasmalemma-enriched microsomes isolated from dog aortic smooth muscle using two different biophysical techniques: fluorescence polarization and electron spin resonance. The calculated membrane fluidity values obtained as a function of temperature by both methods are consistent with the above order of potency. The amount of incorporation of these pyrazine derivatives into the vascular smooth muscle membranes also increased with the increasing hydrophobicity of these drugs, i.e., TMP < 3EP < TEP. Our results are consistent with the contention that these pyrazine derivatives not only interact with receptor protein molecules in the biological membranes, but also modulate these receptor properties via their interaction with the lipid bilayer altering the membrane microviscosity.

Hydrophobic lipid additives affect membrane stability and phase behavior of N-monomethyldioleoylphosphatidylethanolamine.

The rate of formation of high-curvature intermediates or disordered cubic phases in N-methyldioleoylphosphatidylethanolamine (N-methyl-DOPE) dispersions with or without additives was studied by 31P NMR spectroscopy. In N-methyl-DOPE dispersions, both the L alpha liquid-crystalline phase and the hexagonal HII phase convert into phases of high curvature giving rise to isotropic 31P NMR resonances. Addition of the bilayer destabilizers 1,2-diolein, 1,3-diolein, or eicosane lowers the threshold temperature of the isotropic phase. The isotropic threshold temperature is strongly correlated with the L alpha-HII phase transition temperature (TH). The addition of hexagonal phase promoters does not change the rate of formation of the isotropic phase at a temperature shifted by a fixed amount below TH. However, the formation of "isotropic" phases from the additive-stabilized hexagonal phase is slow compared to that observed in pure N-methyl-DOPE lipid dispersions. Membrane leakage and fusion are promoted by the dioleins and well as by eicosane, but changes in the rates of these processes do not correlate well with the extent of formation of isotropic phases. All three additives have similar effects on phase behavior and on vesicle leakage and fusion. These similarities occur despite the fact that eicosane is believed to partition differently into the membrane than diolein. In addition to the general similarities in the effects of the two diolein isomers, 1,2-diolein is somewhat more potent in promoting the hexagonal phase and in increasing rates of leakage and fusion than is 1,3-diolein.

[Effects of indomethacin on 45Ca uptake and membrane fluidity of mitochondria and microsomes from rat liver].

We have reported previously that indomethacin-pretreatment could induce marked hepatic protection in rats. The present work reported effects of indomethacin on calcium regulation and membrane fluidity of mitochondria and microsomes of hepatocytes. The results showed that calcium uptake and membrane fluidity increased significantly in mitochondria and microsomes of hepatocytes isolated from the rats pretreated with indomethacin in vivo as compared with that from the control; adding indomethacin directly to isolated mitochondria and microsomes from normal rats in vitro, on the contrary, decreased membrane fluidity. These changes may be related to the protective effect of indomethacin.