Addition Of High Concentrations Research Articles

Adapting the performance and physico-chemical properties of PES nanofiltration membrane by using of magnesium oxide nanoparticles

A new mixed matrix Polyethersulfone (PES)-co-Magnesium oxide nanoparticles (MGO) nanocomposite nanofiltration membrane was prepared through phase inversion method by using polyvinylpyrrolidone (PVP) as pore former and N, N dimethylacetamide (DMAc) as solvent. The influence of MGO nanoparticles concentration in the membrane matrix on the separation performance and physico-chemical characteristics of prepared membrane was studied by scanning electron microscopy, surface analysis, porosity measurement, water contact angle, permeability flux, salt rejection, antifouling property, and tensile strength. SEM images exhibited situating of MGO nanoparticles on the top surface of mixed matrix prepared membranes. SEM analysis also showed formation of a dense nanoparticle layer on the surface of prepared membrane at high additive concentration. Surface analysis results that revealed membrane surface roughness was increased initially by addition of MGO and then was decreased. Measured porosity showed reduction behavior for all prepared membranes filled with MGO nanoparticles. The membrane surface hydrophilicity was enhanced 35% by incorporating MGO nanoparticles into the membrane matrix. Results showed that membrane permeation flux was improved 32% by utilizing of MgO nanoparticles into the membrane matrix. Salt rejection was also improved 49% by using MGO nanoparticles in the membrane matrix relatively. The modified membranes filled with different concentrations of MGO nanoparticles showed higher antifouling properties and tensile strength compared to the neat PES membrane.

Ultrahigh molecular weight polyethylene/graphene oxide nanocomposites: Wear characterization and biological response to wear particles.

In the field of total joint replacements, polymer nanocomposites are being investigated as alternatives to ultrahigh molecular weight polyethylene (UHMWPE) for acetabular cup bearings. The objective of this study was to investigate the wear performance and biocompatibility of UHMWPE/graphene oxide (GO) nanocomposites. This study revealed that low concentrations of GO nanoparticles (0.5 wt %) do not significantly alter the wear performance of UHMWPE. In contrast, the addition of higher concentrations (2 wt %) led to a significant reduction in wear. In terms of biocompatibility, UHMWPE/GO wear particles did not show any adverse effects on L929 fibroblast and PBMNC viability at any of the concentrations tested over time. Moreover, the addition of GO to a UHMWPE matrix did not significantly affect the inflammatory response to wear particles. Further work is required to optimize the manufacturing processes to improve the mechanical properties of the nanocomposites and additional biocompatibility testing should be performed to understand the potential clinical application of these materials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 183-190, 2018.

Self-floating graphitic carbon nitride/zinc phthalocyanine nanofibers for photocatalytic degradation of contaminants

The effective elimination of micropollutants by an environmentally friendly method has received extensive attention recently. In this study, a photocatalyst based on polyacrylonitrile (PAN)-supported graphitic carbon nitride coupled with zinc phthalocyanine nanofibers (g-C3N4/ZnTcPc/PAN nanofibers) was successfully prepared, where g-C3N4/ZnTcPc was introduced as the catalytic entity and the PAN nanofibers were employed as support to overcome the defects of easy aggregation and difficult recycling. Herein, rhodamine B (RhB), 4-chlorophenol and carbamazepine (CBZ) were selected as the model pollutants. Compared with the typical hydroxyl radical-dominated catalytic system, g-C3N4/ZnTcPc/PAN nanofibers displayed the targeted adsorption and degradation of contaminants under visible light or solar irradiation in the presence of high additive concentrations. According to the results of the radical scavenging techniques and the electron paramagnetic resonance technology, the degradation of target substrates was achieved by the attack of active species, including photogenerated hole, singlet oxygen, superoxide radicals and hydroxyl radicals. Based on the results of ultra-performance liquid chromatography and mass spectrometry, the role of free radicals on the photocatalytic degradation intermediates was identified and the final photocatalytic degradation products of both RhB and CBZ were some biodegradable small molecules.

Protrusion of electroplated copper filled in through silicon vias during annealing process

To investigate the protrusion behavior of the copper filled in through silicon via (TSV), four sets of TSV copper samples are prepared by using four level sets of electroplating current density and additive concentration, and then the samples are annealed with three temperature ramp rates, 10°C/min, 1.2°C/min and 0.6°C/min, respectively. Protrusion of the copper in all of the samples after annealing is measured, and the grain size of the copper before and after annealing is examined. A mechanism of grain size evolution is developed to explain the protrusion process during annealing. A finite element (FE) model is also built up and a grain size dependent material model is introduced to explain the effects of electroplating parameter and annealing temperature ramp rate. Experimental and numerical results show that the sample filled by higher electroplating current density and higher additive concentration has smaller copper grain size both before and after annealing, and also has less protrusion. The protrusion strongly depends on the grain size both before and after annealing. The annealing temperature ramp rate has significant impact on the grain size and protrusion after annealing. The temperature ramp rate affects the protrusion by influencing grain size evolution process, and the mechanism is also validated by FE analysis. After all, an optimized annealing temperature profile is proposed to minimize the copper protrusion by restraining the growth of grain during annealing.

The influence of radical transfer and scavenger materials in various concentrations on the gamma radiolysis of phenol

The influence of a radical scavenger (tert-butanol (t-BuOH)) and two radical transfer materials (formic acid (HCOOH) and formate anion (HCOO−)) on the radical set during radiolysis of a simple model compound, phenol (PhOH, 1.0×10−4molL−1) is discussed in this study. PhOH solutions were irradiated with γ-rays, in the presence of 1.0×10−3, 5.0×10−2 and 5.0×10−1molL−1t-BuOH, HCOOH or HCOONa under deoxygenated and O2-saturated reaction conditions. The rate of transformation of PhOH increased significantly in the presence of dissolved O2. The radical transfer or scavenger materials used reduced the rates of transformation of PhOH in O2-saturated solutions to a similar degree. The simultaneous presence of O2 and the organic additives in excess proportionally to PhOH results in the conversion of the radical set to less reactive intermediates (t-•OOBuOH, HO2• or O2•-), which made minor contribution to the transformation of PhOH. Under oxygenated conditions, t-BuOH and HCOOH in low concentrations slightly promoted the degradation, as opposed to HCOO− which reduced it. However, using higher additive concentrations, their competitive reactions for the primary intermediates came into prominence, thus they reduced the efficiency of PhOH decomposition. HO2• and O2•-, and also the carbon-centred radicals formed (order of their reactivity t-•BuOH>•COOH>CO2•-) have only a minor contribution to the degradation of PhOH, and the reactions of •OH+PhOH and eaq−+PhOH are the significant processes.

Joint Toxicity of Lead, Chromium, Cobalt and Nickel to Photobacterium phosphoreum at No Observed Effect Concentration.

Joint toxicity of Pb2+, Cr3+, Co2+ and Ni2+ toward Photobacterium phosphoreum (Ph. phosphoreum) at the no observed effect concentration (NOEC) was determined through a factorial experiment. A neural network model was designed according to experimental results and employed for toxicity prediction of unary, binary, ternary and quaternary combinations. The mechanism and trends of joint toxicity were interpreted by quantitative structure-activity relationship, Michaelis-Menten kinetic model, and concentration addition (CA) theory. Toxicity was directly related to the covalent index (Xm2r), covalent binding reaction presented a first and zero order reaction at low and high concentration, respectively, and CA accurately predicted toxicity. Additionally, the results showed that low concentrations of heavy metals should be considered when conducting environment risk assessment.

Formation of high-valent cobalt-oxo phthalocyanine species in a cellulose matrix for eliminating organic pollutants

The selective elimination of recalcitrant organic pollutants in high backgrounds of complex constituents has proven a significant challenge. Inspired by the naturally occurring oxidation reactions catalyzed by metalloporphyrin-based enzymes, where the target substrates can be oxidized selectively due to the specific enzyme environment and the axial fifth ligands of metalloporphyrins, we developed a bioinspired catalytic system based on cellulosic fiber-boned cobalt phthalocyanine for capturing and oxidizing dyes by H2O2 activation in the presence of high additive concentrations. In this system, the cellulosic fibers provided the amorphous regions, functioning as cavities in the same manner as the protein backbones of enzymes for the selective accessibility of dyes; cobalt phthalocyanine was introduced as the catalytic entity; and linear alkylbenzene sulfonate (one of the most widespread surfactants in industrial and domestic wastewater) was employed as the fifth ligand to help generate high-valent cobalt-oxo intermediates by the heterolytic cleavage of the peroxide OO bond. According to detailed density functional theory calculations, the spin populations are predominantly located around the cobalt-oxo center, achieving an electrophilic attack on the electron-rich azo bond and the aromatic ring of the target model dyes.

Corrosion performance of rosemary-extract-doped TEOS:TMSM sol-gel coatings on 304L stainless steel

Pure and rosemary-extract-doped hybrid nanostructure coatings have been generated using sols synthesized via acid catalyzed hydrolysis and condensation of methacryloxypropyltrimethoxysilane (TMSM) and tetraethoxysilane (TEOS) at the molar ratio of 1: 1, in combination with rosemary extract. Coatings have been deposited on stainless steel (SS) 304L substrates by spin coating followed by curing at room temperature for 24 h in air and characterized. The morphology, composition and adhesion of hybrid sol-gel coatings have been examined by SEM, EDX and pull-off test, respectively. Addition of high additive concentrations (0.1%) did not disorganize the sol-gel network. Direct pull-off test recorded a mean coating-substrate bonding strength larger than 23.21 MPa for the hybrid sol-gel coating. Corrosion testing of coatings on SS 304L was studied by potentiodynamic polarization measurements and electrochemical impedance spectroscopy after 1 h and 21 days exposure to the physiological saline solution. The corrosion resistances of hybrid rosemary-extract-doped coatings after 1 h and 21 days exposure to the physiological saline solution were higher than that of pure hybrid silica coatings, both of which had thicknesses ranging lower than 100 nm. Also the electrochemical beha-viors of doped coating were studied by potentiodynamic polarizations tests in 3.5% NaCl media and the results were shown that this system is applicable in industry.

Active biocomposites of cassava starch: The effect of yerba mate extract and mango pulp as antioxidant additives on the properties and the stability of a packaged product

There is an increasing interest in the utilization of renewable resources for the production of food packaging. Among the biopolymers, starches from several sources are considered promising materials for this purpose, because they are biodegradable, inexpensive and available worldwide. Antioxidant food packaging films were produced by incorporating mango pulp and yerba mate extract into a cassava starch matrix. The bio-based films were used to pack palm oil (maintained for 90 days of storage) under accelerated oxidation conditions (63% RH/30°C) in order to simulate a storage experiment. Palm oil packaged in these films exhibited a decreased oxidative process rate, which was attributed to the yerba mate and mango pulp in a concentration-dependent fashion. The evolution of the peroxide value contents indicated that, in general, the films with high concentrations of additives improved palm oil stability. Mechanical, physical and barrier properties of the developed film indicated that the addition of these bioactive compounds modified their properties significantly (p<0.05).

225 OXIDATIVE STRESS AND MEMBRANE INTEGRITY OF CRYOPRESERVED SPERMATOZOA WITH VITAMIN C

Disturbances in oxidant/production in favour of oxidizing cause oxidative stress during the cryopreservation process. Vitamin C is an antioxidant non-enzymatic present in seminal plasma that protects sperm from oxidative stress. The aim of this study was to evaluate supplementation with ascorbate in a cryopreservation medium on oxidative stress and quality of cryopreserved sperm membranes. It was used in 24 bulls averaging 31 months and 732 kg, kept on pasture for this experiment. One ejaculate was collected from each breeder by electrostimulation. The treatments were CO-Control (no additives) and AS-ascorbate (0.45 mg mL–1). Ascorbate was added to diluted semen at the time of filling in 0.5-mL straws before the cryopreservation process. Thawing was performed in a water bath at 37°C for 30 s. After thawing the samples, aliquots for assessment of plasma and acrosome membrane integrity and evaluation of oxidative stress [TBARS concentration spontaneous (TE) and induced (TI)] were taken. The experiment was conducted in a completely randomised design. Data were analysed by ANOVA and compared by the Tukey average test with a significance level of 5%. No differences were observed (CO- 31.67 ± 2.81 v. AS- 31.08 ± 2.42, P &gt; 0.05); the quality of the sperm membrane and oxidative stress (TECO: 5.98 ± 2.13 v. TEAS: 6.62 ± 2.33, P &gt; 0.05 and TICO: 62.34 ± 8.22 v. TIAS: 58.52 ± 8.27, P &gt; 0.05) in sperm cryopreserved with ascorbate were similar to the control group. Typically, animals under adequate nutritional conditions produce adequate amounts of ascorbate; perhaps because of that the treatment using exogenous ascorbate did not present a significant result. The supplementation of extender with ascorbate did not affect oxidative stress and the quality of the plasma membrane and acrosome sperm cryopreserved. Preliminary studies had shown that the addition of higher concentration (4,5 mg mL–1) of ascorbate has a beneficial effect on oxidative stress and membrane integrity (P &lt; 0.05). Thus, further research should be done to better understand the effects of ascorbate in bovine semen.

Preparation and Performance of Hydroxypropyl Methylcellulose Esters of Substituted Succinates for in Vitro Supersaturation of a Crystalline Hydrophobic Drug

We prepared hydroxypropyl methylcellulose (HPMC) esters of substituted succinates and examined their performance for improving the aqueous solubility of crystalline hydrophobic drugs in spray-dried dispersions (SDDs). From one HPMC, we synthesized five HPMC esters using various monosubstituted succinic anhydrides. These HPMC esters along with a commercial HPMC acetate succinate (HPMCAS) were spray-dried from solutions with phenytoin. The SDDs with different matrices at 10 wt % loading had very similar bulk properties with a minimal amount of detectable crystalline phenytoin as revealed by scanning electron microscopy (SEM), powder X-ray diffraction (powder XRD), and differential scanning calorimetry (DSC). In solution, while the SDD with HPMCAS was very effective at achieving high levels of phenytoin supersaturation initially, it was not competent at maintaining such supersaturation due to the rapid crystallization of the dissolved phenytoin. Alternatively, SDDs with several synthesized HPMC esters of substituted succinates not only achieved rather high initial supersaturation but also maintained high concentrations for extended time (i.e., 1.5 h and longer). Such maintenance was largely ascribed to the inhibition of phenytoin nucleation. Structure-property relationships were established, and the most successful systems contained a high degree of substitution and a combination of a thioether with neighboring weak electron-withdrawing groups in the substituted succinic anhydrides. The effective maintenance of supersaturated solutions was only found in SDDs with rather low drug loadings, which indicates the significance of sufficiently high concentrations of polymer additives in the dissolution media.

The influence of hydrophilic properties on the venting of foamy three phase systems

The correct design of a safety valve or rupture disk can only be done if predictions on the venting behavior can be made. To date, those predictions have limitations with regard to foaming or highly viscous systems. An experimental study is presented that describes the influence of hydrophilic particles on the venting of strongly and weakly foaming systems. It is shown that hydrophilic particles increase the mass discharge over time and reduce the pressure decrease over time by increasing the foaming of aqueous systems. These effects are not significantly influenced by the reactor characteristics. At higher additive concentrations, the addition of particles is not as influential anymore. Thus, models for foamy two‐phase systems are applicable for the design of the described foamy three‐phase systems as well. © 2013 American Institute of Chemical Engineers Process Saf Prog 32: 239–243, 2013

Kinetics and Mechanisms of Radical-Based Branching/Cross-Linking Reactions in Preformed Polymers Induced by Benzophenone and Bis-Benzophenone Photoinitiators

The general mechanism for photo-cross-linking of preformed polymers is studied by comparing the efficacy of monofunctional benzophenone (BP) and bifunctional bis-benzophenone (BP-BP) photoinitiators for inducing radical chain branching reactions in glassy polystyrene (PS) and rubbery poly(n-butyl acrylate) (PnBA). Upon UV irradiation, macroradicals form and initiate a variety of cross-linking and scission reactions. The kinetics and mechanisms of these macroradical reactions were monitored by gel permeation chromatography (GPC) measurements of changes in the polymer molecular weight distributions. Molecular weight increases are associated with chain branching while decreases in molecular weight are indicative of chain scission. We study the early stages of radical recombination where branching is manifest as the formation of three- and four-arm star polymers that are soluble and can be detected/differentiated by GPC. Branching is observed even in glassy PS; however, the reactions are much faster in rubbery PnBA, consistent with the expected influence of main chain mobility. At equal chromophore equivalents, BP-BP was found to be more efficient than BP for producing macroradicals, primarily due to a lower degree of self-quenching in BP-BP. When added to glassy PS, the higher efficiency of BP-BP did not translate into more chain branching, except at high additive concentration where the probability of BP-BP chain bridging reactions becomes significant, but instead led to a higher degree of main chain scission. The latter result was attributed to the larger distance between chromophores for BP-BP than for BP at equal benzophenone equivalents. In marked contrast, almost no main chain scission was found for either additive in PnBA, and BP-BP proved more effective for promoting chain branching. The susceptibility to main chain scission is found to be dependent upon the location of radical formation by hydrogen abstraction from the polymer. In PS, radicals can form on the chain backbone, and radical scission reactions lead to fragmentation of the polymer chain. In PnBA, radicals form preferentially on the pendant side chains, and radical scission reactions do not lead to main chain breakage. A simple probability-based model was found to capture the salient features of radiation-induced branching in preformed polymers.

Solid-state solvent-free catalyzed hydrogenation: Enhancing reaction efficiency by spillover agents

The adsorption kinetics of hydrogen on solid support is accelerated by three orders of magnitude upon adding carbon nanotubes (CNT) to the support. The gas–solid catalytic hydrogenation is studied at ambient temperature and sub atmospheric pressure while the support consists of a mixture of nano Pd-on-carbon with unsaturated hydrocarbon H-acceptor. The addition of a small amount of pristine CNT minimizes the required Pd concentration. A similar effect is demonstrated by addition of different oxides to the composite, but at much higher additive concentrations. The addition of the spillover agent improves the transport of the hydrogen atoms in the composite to remote sites with low Pd concentration via a spillover mechanism. Therefore, it is possible to overcome the decelerating effect of inhomogeneity in the support. The irreversible gas–solid hydrogenation could serve as a simplified platform to study the slower step of hydrogen spillover, which operates also in hydrogen storage processes.

Effect of process parameters on micro and macro-properties of an Al-based nanocomposite prepared by means of mechanical milling

Abstract In this research, some Al-based composites reinforced with silica nanoparticles were fabricated using mechanical milling and processing by powder metallurgy. Density, morphology evolution, hardness and strength of the composites were studied as a function of milling time and additive concentration. Microstructural evidence reveals that milling conditions generated a uniform dispersion of nanoparticles in the Al matrix. Noticeable matrix grain refinement was induced by the milling process. An optimum mechanical response was reached with small amounts of reinforcement nanoparticles complemented with medium milling intensities. These manufacturing conditions allowed to achieve an improvement of mechanical properties compared with the reference material (pure milled Al and un-milled composites processed under the same conditions). On the other hand, an adverse effect was observed with longer milling time and higher additive concentration.

Physicochemical properties of soy protein isolate gels emulsified with various oils using a microbial transglutaminase

Soy protein isolate (SPI) gels emulsified with oils including soybean, olive, palm, and eicosapentaenoic acid (EPA) were prepared by a microbial transglutaminase (MTGase). The hardness of 10% SPI gel was greatly increased by adding higher amount of oils. The emulsion gels prepared with 10% SPI and 30% olive oil showed the highest hardness of 1,711 g. In the gelation with various oil content (5–30%), the higher concentration of oils indicated the drastic increase of elastic modulus G′ and viscous modulus G″ during initial gelation for 7 min. The G′ value of SPI emulsion gel showed the 150 (soybean oil 30%), 147 (olive oil 30%), 121 (palm oil 30%), and 61 Pa (EPA 25%), respectively. In the color value of SPI emulsion gel, addition of higher concentration of oils resulted in the increase of L value (brightness), indicating 99.14 (L value) at 30% palm oil. The micro-structure of SPI emulsion gel entrapped with various oils showed the homogeneous network with small porosity compared with that of SPI gel without oil. In particular, SPI emulsion gel with 10% palm oil showed the compact structure distributed evenly with small porosity. Conclusively, the functional and rheological properties of SPI emulsion gel produced by catalytic action of MTGase could be modulated by the type and content of oils fortified.

Electrochemical and In Vitro Behavior of Nanostructure Sol-Gel Coated 316L Stainless Steel Incorporated with Rosemary Extract

The corrosion resistance of AISI 316L stainless steel for biomedical applications, was significantly enhanced by means of hybrid organic-inorganic sol-gel thin films deposited by spin-coating. Thin films of less than 100 nm with different hybrid characters were obtained by incorporating rosemary extract as green corrosion inhibitor. The morphology, composition, and adhesion of hybrid sol-gel coatings have been examined by SEM, EDX, and pull-off test, respectively. Addition of high additive concentrations (0.1%) did not disorganize the sol-gel network. Direct pull-off test recorded a mean coating-substrate bonding strength larger than 21.2 MPa for the hybrid sol-gel coating. The effect of rosemary extract, with various added concentrations from 0.012 to 0.1%, on the anticorrosion properties of sol-gel films have been characterized by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in simulated body fluid (SBF) solution and has been compared to the bare metal. Rosemary extract additions (0.05%) have significantly increased the corrosion protection of the sol-gel thin film to higher than 90%. The in vitro bioactivity of prepared films indicates that hydroxyapatite nuclei can form and grow on the surface of the doped sol-gel thin films. The present study shows that due to their excellent anticorrosion properties, bioactivity and bonding strength to substrate, doped sol-gel thin films are practical hybrid films in biomedical applications.

Improvement of corrosion performance of 316L stainless steel via PVTMS/henna thin film

Metallic materials are the most used materials as orthopedic or dental implants due to their excellent mechanical properties. However they are not able to create a natural bonding with the mineralized bone and occasionally suffer localized corrosion. This work describes the electrochemical behavior of a hybrid sol–gel thin film with the addition of green inhibitor. These films enhance the ability of the implant to make a union with the existing bone and improve its resistance to aggressive environment. An ethanol solution of the polymerized vinyltrimethoxysilane (PVTMS) was mixed with an aqueous solution of henna extract (Lawsonia inermis) and refluxed to give homogeneous sols. Nanostructure hybrid PVTMS/henna thin films were deposited on the stainless steel 316L by spin-coating. The morphology, composition and adhesion of hybrid sol–gel coatings have been examined by SEM, EDX and pull-off test, respectively. Addition of high additive concentrations (0.1%) did not disorganize the sol–gel network. Direct pull-off test recorded a mean coating-substrate bonding strength larger than 20.6MPa for the hybrid sol–gel coating. The effect of henna extract, with various added concentrations from 0.012% to 0.1%, on the anticorrosion properties of sol–gel films have been characterized by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in simulated body fluid (SBF) solution and has been compared to the bare metal. Henna extract additions (0.05%) have significantly increased the corrosion protection of the sol–gel thin film to higher than 90%. The in vitro bioactivity of prepared films indicates that hydroxyapatite nuclei can form and grow on the surface of the doped sol–gel thin films. The present study shows that due to their excellent anticorrosion properties, bioactivity and bonding strength to substrate, doped sol–gel thin films are practical hybrid films in biomedical applications.

Tribological Characteristics of Three Novel Imidazoline-Type Thiadiazole Derivatives in Colza Oil and Synthetic Diester

Owing to the requests of exploring environment-friendly and multifunctional lubricant additives, three novel imidazoline-type thiadiazole derivatives are prepared and used as lubricant additives in two biodegradable base stocks, colza oil and synthetic diester, respectively, and their tribological performance is tested using the four-ball tester. For further understanding of their tribological behaviors, x-ray absorption near edge structure (XANES) spectroscopy is adopted to analyze the thermal films and tribofilms generated from these additives in two base stocks. Tribological tests show that all these thiadiazole derivatives are effective in reducing wear in synthetic diester, and derivative SIB (stearic acid-imidazoline-type thiadiazole derivative) is better than derivative OIB (oleic acid-imidazoline-type thiadiazole derivative) and derivative DIB (lauric acid-imidazoline-type thiadiazole derivative) in reducing friction at high additive concentrations. But these derivatives almost fail in improving the tribological characteristic of colza oil. According to XANES spectra, thermal films formed in two base stocks are mainly composed of ferrous sulfate and adsorbed organic sulfide. These derivatives are also easily oxidized into high-valent sulfate in colza oil during the rubbing process, and ferrous sulfate is the main component of these tribofilms. But in synthetic diester, tribofilms are mainly composed of ferrous sulfide, and it is notable that the tribofilm generated by derivative SIB at 1.0 wt. % is composed of ferrous sulfide and ferrous disulfide. Under extreme-pressure conditions, these derivatives easily react with the metallic surface to generate ferrous sulfide in colza oil. But in synthetic diester, adsorbed organic sulfide is the main component of those films. The base stock has a great impact on the compositions of these reaction films, so the tribological behaviors of these derivatives are different in two base stocks.

Tobacco etch virus protease retains its activity in various buffers and in the presence of diverse additives

Tobacco etch virus (TEV) protease is widely used to remove tags from recombinant fusion proteins because of its stringent sequence specificity. It is generally accepted that the high concentrations of salts or other special agents in most protein affinity chromatography buffers can affect enzyme activity, including that of TEV protease. Consequently, tedious desalination or the substitution of standard TEV reaction buffer for elution buffer are often needed to ensure TEV protease activity when removing fusion tags after purifying target proteins using affinity chromatography. To address this issue, we used SOE PCR technology to synthesize a TEV protease gene with a codon pattern adapted to the codon usage bias of Escherichia coli, recovered the purified recombinant TEV protease, and examined its activity in various elution buffers commonly used in affinity chromatography as well as the effects of selected additives on its activity. Our results showed that the rTEV protease maintained high activity in all affinity chromatography elution buffers tested and tolerated high concentrations of additives commonly used in protein purification procedures, such as ethylene glycol, EGTA, Triton X-100, Tween-20, NP-40, CHAPS, urea, SDS, guanidine hydrochloride and β-mercaptoethanol. These results will facilitate the use of rTEV protease in removing tags from fusion proteins.