Molar Ratio Mixture Research Articles

Sheet‐Like Assemblies of Charged Amphiphilic α/β‐Peptides at the Air–Water Interface

There is growing interest in the design of molecules that undergo predictable self-assembly. Bioinspired oligomers with well-defined conformational propensities are attractive from this perspective, since they can be constructed from diverse building blocks, and self-assembly can be directed by the identities and sequence of the subunits. Here we describe the structure of monolayers formed at the air-water interface by amphiphilic α/β-peptides with 1:1 alternation of α- and β-amino acid residues along the backbone. Two of the α/β-peptides, one a dianion and the other a dication, were used to determine differences between self-assemblies of the net negatively and positively charged oligomers. Two additional α/β-peptides, both zwitterionic, were designed to favor assembly in a 1:1 molar ratio mixture with parallel orientation of neighboring strands. Monolayers formed by these α/β-peptides at the air-water interface were characterized by surface pressure-area isotherms, grazing incidence X-ray diffraction (GIXD), atomic force microscopy and ATR-FTIR. GIXD data indicate that the α/β-peptide assemblies exhibited diffraction features similar to those of β-sheet-forming α-peptides. The diffraction data allowed the construction of a detailed model of an antiparallel α/β-peptide sheet with a unique pleated structure. One of the α/β-peptide assemblies displayed high stability, unparalleled among previously studied assemblies of α-peptides. ATR-FTIR data suggest that the 1:1 mixture of zwitterionic α/β-peptides assembled in a parallel arrangement resembling that of a typical parallel β-sheet secondary structure formed by α-peptides. This study establishes guidelines for design of amphiphilic α/β-peptides that assemble in a predictable manner at an air-water interface, with control of interstrand orientation through manipulation of Coulombic interactions along the backbone.

Characterization of Cu 3SbS 4 microflowers produced by a cyclic microwave radiation

Copper antimony sulfide (Cu 3SbS 4) crystals were produced from mixtures of different molar ratios of CuCl, SbCl 3 and thiourea in 40 and 60 ml ethylene glycol (EG) by a 300 W cyclic microwave radiation (CMR) for different lengths of time. In the present research, tetragonal Cu 3SbS 4 microflowers, characterized by X-ray and electron diffraction including electron microscopy and Raman analyses, were successfully produced in the 40 ml solution containing 2:2:4 molar ratio Cu:Sb:S for 40 cycles. Their UV-visible absorption was studied to determine the energy gap (E g). A formation mechanism was also proposed to relate with the experimental results.

Feasibility and performance of the mixture of MgH 2 and LiNH 2 (1:1) as a hydrogen-storage material

A 1:1 molar ratio mixture of MgH 2 and LiNH 2 was predicted to release 8.1 wt.% H under moderate conditions. This binary mixture of MgH 2–LiNH 2 was found to be a multinary complex system induced by mechanical ball milling, due to the metathesis reaction between the initial components. It was found that dehydrogenation from this system was initialized by the formation of LiH and Mg(NH 2) 2 via such metathesis. The hydrogen sorption performance studied in this work shows a strong influence of the ball-milling parameters which determine the subsequent dehydrogenation pathways. An adequate ball milling facilitates hydrogen release, whereas insufficient milling results in a sluggish hydrogen desorption and severe NH 3 emission. A maximum amount of 7.3% was obtained with formation of the ternary nitride LiMgN; however, desorption temperatures of up to 600 °C had to be applied.

Protease activation in glycerol-based deep eutectic solvents

Deep eutectic solvents (DESs) consisting of mixtures of a choline salt (chloride or acetate form) and glycerol are prepared as easily accessible, biodegradable, and inexpensive alternatives to conventional aprotic cation-anion paired ionic liquids. These DES systems display excellent fluidity coupled with thermal stability to nearly 200 °C. In this work, the transesterification activities of cross-linked proteases (subtilisin and α-chymotrypsin), immobilized on chitosan, were individually examined in these novel DESs. In the 1:2 molar ratio mixture of choline chloride/glycerol containing 3% (v/v) water, cross-linked subtilisin exhibited an excellent activity (2.9 μmo l min(-1) g(-1)) in conjunction with a selectivity of 98% in the transesterification reaction of N-acetyl-L-phenylalanine ethyl ester with 1-propanol. These highly encouraging results advocate more extensive exploration of DESs in protease-mediated biotransformations of additional polar substrates and use of DESs in biocatalysis more generally.

The effect of hydroxocobalamin on the nitroprusside-induced relaxation of rat aortic preparations.

Hydroxocobalamin (HOCb) when mixed with sodium nitroprusside (SNP) in a 10:1 or 1:1 molar ratio had no significant effect on the relaxation of noradrenaline-precontracted rat aortic rings. However, the addition of HOCb did prolong the time taken for the relaxant response to occur. The time taken for a 0.34 microM SNP dose to exert 50% of its relaxant effect was increased by about 120 and 35% with 10:1 and 1:1 HOCb/SNP molar ratio mixtures, respectively. A 0.5:1 HOCb/SNP molar ratio mixture caused no prolongation. In incubations with [14C]SNP, it was found that mixing with equimolar, or greater, amounts of HOCb, reduced aortic tissue uptake of radioactivity. The results support the hypothesis that both SNP alone and SNP/HOCb complexes breakdown extracellularly to release the same amount of active species, but that in the case of the complexes the active agent is released at a slower rate.

Mixed Charged Zwitterionic Self-Assembled Monolayers as a Facile Way to Stabilize Large Gold Nanoparticles

Here we report a facile way of stabilizing large gold nanoparticles (AuNPs) by mixed charged zwitterionic self-assembled monolayers (SAMs). The citrate-capped AuNPs with diameters ranging from 16 nm to even ∼100 nm are well stabilized via a simple place exchange reaction with a 1:1 molar ratio mixture of negatively charged sodium 10-mercaptodecanesulfonic acid (HS-C10-S) and positively charged (10-mercaptodecyl)-trimethyl-ammonium bromide (HS-C10-N4). The 16 nm AuNPs protected by mixed charged zwitterionic SAMs not only show much better stability than the single negatively or positively charged AuNPs, but also exhibit exciting stability as well as those modified by monohydroxy (1-mercaptoundec-11-yl) tetraethylene glycol (HS-C11-EG4). Importantly, 16 nm AuNPs protected by mixed SAMs exhibit good stability in cell culture medium with 10% FBS and strong protein resistance, especially with excellent resistance against plasma adsorption. Moreover, the mixed charged zwitterionic SAMs are also able to well-stabilize larger AuNPs with a diameter of 50 nm, and to help remarkably improve their stability in saline solution compared with HS-C11-EG4 protected ones. When it comes to AuNPs with a diameter of 100 nm, the mixed charged zwitterionic SAM protected nanoparticles retain a smaller hydrodynamic diameter and even better long-term stability than those modified by mercaptopolyethylene glycol (M(w) = 2000, HS-PEG2000). The above results demonstrated that the mixed charged zwitterionic SAMs are able to have a similar effect on stabilizing the large gold nanoparticles just like the single-component zwitterionic SAMs. Concerning its ease of preparation, versatility, and excellent properties, the strategy based on the mixed charged zwitterionic SAM protection might provide a promising method to surface tailoring of nanoparticles for biomedical application.

Molar ratio mixture design for optimising compressive strength of kaolinitic cement

Molar ratio mixture design for optimising compressive strength of kaolinitic cement

Compressibility and Elasticity of Amphiphilic and Acidic β-Sheet Peptides at the Air−Water Interface

Grazing incidence X-ray diffraction measurements were performed on monolayer films of three amphiphilic and acidic β-sheet peptides having the general sequence Pro-Y-(Z-Y)(5)-Pro, with Y = Asp or Glu and Z = Phe or Leu denoted, P(FD)-5, P(LE)-5, P(LD)-5, and the 1:1 molar ratio mixture of P(LD)-5 and P(LE)-5. The crystalline domains of these peptides exhibited compressibility and elasticity of the crystalline unit cell indicated by changes in diffraction patterns on compression. Higher compressibility values appeared to be associated with more favorable cross-strand interactions between peptides with the larger side chains, whereas P(LD)-5, decorated by the smaller side chain amino acids, exhibited the lowest crystalline compressibility. Diffraction patterns provided evidence for a new subunit cell generated by the pleated β-strand motif in an apparently favorable mode of cross-strand intermolecular packing in β-sheets. The study contributes to the understanding of β-sheet flexibility at interfaces with relevance to natural proteins and designed biomaterials composed of β-sheet peptides.

Effect of a combination of deoxynivalenol and nivalenol on lipopolisaccharide-induced nitric oxide production by mouse macrophages

Deoxynivalenol (DON) and nivalenol (NIV) are trichothecene mycotoxins produced by Fusarium fungi as secondary metabolites. Both compounds have the immunotoxic effects that the productions of inflammatory mediators by activated macrophages is disturbed. Co-contamination with DON and NIV can occur; however, the effects of simultaneous contamination are not well known. The present study investigated the combined effects of DON and NIV on nitric oxide (NO) production by mouse macrophages stimulated with lipopolisaccharide (LPS). The inhibitory effect of DON and NIV on NO release from activated macrophages has already been reported as an appropriate indicator of immunotoxic effect of the both compounds. LPS-induced NO production in macrophages was inhibited by both of these toxins individually in a dose-dependent manner, and toxin mixtures at the same concentration inhibited NO production in the same manner. In addition, there were no unique inhibitory effects on LPS-induced NO production in macrophages in the presence of mixtures of various molar ratios. These results suggest that the combined effects of DON and NIV can be predicted based on addition of each compound alone.

저온 photoluminescence 스펙트럼 및 형광체 합성에 관한 연구

In this paper, synthesis here Mn add to Ar injection the state and a vacuum an atomosphere : Mn, ZnO and power of 1 : 1 mole ratio mixture. Manufacture a close examination of oxygen a component variation luminescence a specific character reach an in fluence of : Mn, luminescence spectrum observation also an explanation of Mn site symmetry and at luminescence spectrum reach an influence from low temperature photoluminescence spectrum.

Adsorption of arsenic using high surface area magnetites

Magnetites (MEBWx) were prepared by precipitation in 1-butanol/water mixtures of various mole ratios of 1-butanol to water. It was found that the magnetites prepared in the mixture with high mole ratio of 1-butanol to water have high specific surface area. The adsorption isotherms of As(III) and As(V) with the magnetites at 303 K fitted the Langmuir model well. The adsorption capacities of the magnetite prepared in the mixtures were higher than those of the magnetite prepared without 1-butanol. Their adsorption capacities increased with increasing specific surface area.

The Key Physiological Response to Alkali Stress by the Alkali‐Resistant Halophyte Puccinellia tenuiflora is the Accumulation of Large Quantities of Organic Acids and into the Rhyzosphere

AbstractEight‐week‐old seedlings of Puccinellia tenuiflora were stressed by exposure to 1 : 1 molar ratio mixtures either of the two neutral salts NaCl and Na2SO4 or of the two alkali salts, NaHCO3 and Na2CO3. To identify the physiological mechanisms involved in this plant’s resistance to alkali stress, the relative growth rates, the quantities and compositions of organic acids accumulated and secreted through the roots into the rhyzosphere, the concentrations of inorganic ions, proline and other solutes accumulating in the shoots were measured. The results show that the organic acid constituents in the shoots and roots were much the same. These were predominantly malic acid, oxalic acid, citric acid and succinic acid. The total concentration of organic acids in the shoots increased strongly with increasing alkali stress. However, these either did not increase or they decreased slightly with increasing salt stress. Of the four organic acids, the concentration difference between salt‐ and alkali‐stressed plants was most striking for citric acid. This became the dominant organic acid component under alkali stress. Results show that proline is the main organic osmolyte, whereas the contribution of betaine to osmotic adjustment is insignificant under either salt or alkali stress. The main organic acid accumulated was not only an important organic osmotic regulator, but also an important negative charge contributor, playing important roles in ionic balance and pH adjustment. The concentrations of Na+, K+, Cl− and of organic acid were 80.7% of all solutes under salt stress. The concentrations of Na+, K+, Cl− and of organic acid were 85.4% of all solutes under alkali stresses. The ionic balance was disrupted by the strong increase in Na+ content under alkali stress. This perhaps explains why large amounts of the organic acids were accumulated. The organic acid concentration in the roots was lower than in the shoots. The roots secreted citric acid into the rhyzosphere only under alkali stress, secretion of the other organic acids was not detected. Therefore, citric acid secreted from the roots probably plays an important role in pH adjustment in the rhyzosphere of P. tenuiflora.

The effects of ball milling and molar ratio of LiH on the hydrogen storage properties of nanocrystalline lithium amide and lithium hydride (LiNH2+LiH) system

Abstract High-energy ball milling was applied to the mixtures of LiNH 2 and LiH having the molar ratio 1:1, 1:1.2 and 1:1.4LiH. During a high-energy ball milling of the 1:1 molar ratio mixture the grain (crystallite) size of LiNH 2 and LiH constituent decreases monotonically with increasing milling time while the specific surface area (SSA) of powder increases up to 25 h of milling duration and then decreases after milling for 100 h due to the excessive agglomeration of powder particles into lumps. A single-phase LiNH 2 decomposes through melting and the release of ammonia (NH 3 ). A just mixed LiNH 2 + LiH mixture still mostly decomposes through the melting of LiNH 2 and release of NH 3 . For the hydrogen to be effectively released from the mixture of (LiNH 2 + LiH) a high-energy ball milling is necessary which makes an intimate contact between both constituents. The activation energy for hydrogen desorption from the ball milled mixture of (LiNH 2 + LiH) decreases with increasing SSA of powders up to ∼26 m 2 /g and then levels off with further increase of SSA. For the ball milled mixture of LiNH 2 :LiH the lowest activation energy is observed for the molar ratio of 1:1.2LiH. The hydrolysis/oxidation of the fraction of LiH into LiOH in the mixture makes a fraction of LiH inactive in the intermediate reaction NH 3 + LiH → LiNH 2 + H 2 and creates the major obstacle to the hydrogen desorption from the ball milled mixture of LiNH 2 + LiH. At the molar ratio 1:1.2 of LiNH 2 :LiH the mass of the active LiH is the largest one which leads to the largest quantity of desorbed hydrogen (∼5 wt.%). The amount of hydrogen desorbed from LiNH 2 + LiH slightly decreases with increasing milling time from 5 to 100 h due to the reduction in grain (crystallite) size of LiH which renders it more sensitive to hydrolysis and the formation of LiOH.

Pd–Ag membranes for auto‐thermal ethanol reforming

AbstractThe auto‐thermal ethanol reforming was carried out at 200 kPa by a two‐step process consisting of a traditional reformer operating at high temperature (700–740 °C) and a Pd–Ag multitube membrane module where the separation of hydrogen took place at 350–380 °C.The membrane module was a bundle of 11 thin‐wall Pd–Ag tubes of wall thickness 50–60 µm, diameter 10 mm, and length 270 mm: permeation tests were performed at 300–395 °C with lumen pressure of 150–200 kPa, and nitrogen sweep flow rates in the shell side ranged from 10 to 30 l min−1 at atmospheric pressure. A hydrogen permeance Pe = 1.317 × 10−2 exp (−3.622 × 103/T(K)) mol m−2 s−1 Pa−0.5 was measured and complete hydrogen selectivity was verified.A water/ethanol mixture of molar ratio 2.50/1.00 was used as feed stream for carrying out ethanol reforming in the traditional fixed‐bed reactor filled with a Ni on alumina catalyst. As a second step, the water gas shift (WGS) membrane reaction was carried out in the multitube membrane reactor: the Pd–Ag alloy of the membrane tubes worked for both catalyzing the reaction and for separating all the hydrogen produced in the reformer and in the membrane reactor itself. The hydrogen separated through the membrane was collected in the shell side of the membrane module: by operating with a water/ethanol feed flow rate of 200 g h−1, up to 1.2 l min−1 of pure hydrogen was produced. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

Lipase-catalyzed acidolysis of fish liver oil with dihydroxyphenylacetic acid in organic solvent media

Lipase-catalyzed acidolysis reaction of fish liver oil with dihydroxyphenylacetic acid (DHPA) was investigated in terms of enzyme specificity as well as the effects of enzyme concentration, molar substrate ratio and organic solvent mixture on the bioconversion yield. The highest bioconversion yield of 83% was obtained when Novozym 435 was used as biocatalyst in a hexane:2-butanone mixture of 75:25 (v/v) at a fish liver oil to DHPA substrate molar ratio of 4:1; however, lower bioconversion yield (15%) was obtained when Lipozyme IM 20 was used. The bioconversion yield of phenolic monoacylglycerols (MAGs) increased from 11 to 70% when the ratio of the hexane/2-butanone reaction medium was changed from 85:15 to 75:25 (v/v), whereas that of phenolic diacylglycerols (DAGs) remained relatively unchanged (13–16%). The results also showed that the acidolysis reaction resulted in an increase of C 20:5 ω-3 and C 22:6 ω-3 proportions from 11.5 and 20.2% in the original fish liver oil to 22.6–27.1 and 22.8–23.1% in the phenolic lipids, respectively. The radical scavenging ability of phenolic lipids was determined to be about half-time lower than that of α-tocopherol.

Curing of diglycidyl ether of bisphenol‐A epoxy resin using a poly(aryl ether ketone) bearing pendant carboxyl groups as macromolecular curing agent

AbstractBACKGROUND: Reactive thermoplastics have received increasing attention in the field of epoxy resin toughening. This paper presents the first report of using a novel polyaryletherketone bearing one pendant carboxyl group per repeat unit to cure the diglycidyl ether of bisphenol‐A epoxy resin (DGEBA). The curing reactions of DGEBA/PEK‐L mixtures of various molar ratios and with different catalysts were investigated by means of dynamic differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy methods.RESULTS: FTIR results for the DGEBA/PEK‐L system before curing and after curing at 135 °C for different times demonstrated that the carboxyl groups of PEK‐L were indeed involved in the curing reaction to form a crosslinked network, as evidenced by the marked decreased peak intensities of the carboxyl group at 1705 cm−1 and the epoxy group at 915 cm−1 as well as the newly emerged strong absorptions of ester bonds at 1721 cm−1 and hydroxyl groups at 3447 cm−1. Curing kinetic analysis showed that the value of the activation energy (Ea) was the highest at the beginning of curing, followed by a decrease with increasing conversion (α), which was attributed to the autocatalytic effect of hydroxyls generated in the curing reaction.CONCLUSION: The pendant carboxyl groups in PEK‐L can react with epoxy groups of DGEBA during thermal curing, and covalently participate in the crosslinking network. PEK‐L is thus expected to significantly improve the fracture toughness of DGEBA epoxy resin. Copyright © 2009 Society of Chemical Industry

Aptamer biosensor for lable-free detection of human immunoglobulin E based on surface plasmon resonance

Aptasensor, an aptamer-based sensor for non-labeled detection of human immunoglobulin E (IgE), was developed using surface plasmon resonance (SPR). Various oligo(ethylene glycol) mixtures of different molar ratios of EG 6-COOH and EG 3-OH were used for the construction of self-assembled monolayers (SAM). Direct assays and modified sandwich assays over a 1.0 nM anti-IgE, aptamer-immobilized, gold chip, consisting of a 1:3 molar ratio of EG 6-COOH:EG 3-OH SAM, were investigated for real-time IgE detection. The linear ranges for both were 1.0–1000 ng/mL and the lowest amounts of detectable analytes in the samples were 3.44 and 2.07 ng/mL for direct and modified sandwich assays, respectively. These results for IgE detection suggest that the aptamer offers the possibility of a simple and realistic biosensor platform based on a SAM-fabricated SPR system. Furthermore, as an optic-biosensor, an SPR aptasensor could be used for the diagnosis of allergies.

Bulk modulus and thermal expansion coefficient of mechano-chemically synthesized Mg2FeH6 from high temperature and high pressure studies

Abstract Mg2FeH6 was synthesized by ball milling MgH2 and Fe (2:1 molar ratio) mixture for 72 h followed by heating at 400 °C under H2 pressure. The hydride formation, its structure and homogeneity were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and Raman spectroscopy. High pressure in situ synchrotron X-ray diffraction and Vienna ab initio simulation were used to determine bulk modulus of the sample. The bulk modulus of Mg2FeH6 was found to be 75.4(4) GPa by optimized experiment and 76.3 GPa by theoretical simulation. From high temperature in situ X-ray diffraction study the volumetric thermal expansion coefficient of Mg2FeH6 was found to be αv = 5.85(3) × 10−5 + 7.47(7) × 10−8 (T − To)/°C. Decomposition of Mg2FeH6 was observed at 425 °C and the decomposition products were Mg, Fe and H2.

4-Isopropylpyridine Hydroperoxide Crystals Resulting from the Aerobic Oxidation of a 4-Isopropylpyridine/4-Propylpyridine Mixture

We model the interaction of side-chain and end-chain groups of poly(4-vinylpyridine) by a 5:1 molar ratio mixture of 4-isopropylpyridine (side-chain model) and 4-propylpyridine (end-chain model). We find that the 4-isopropylpyridine in the mixture is oxidized in a slow air flow to produce 4-isopropylpyridine hydroperoxide which in turn precipitates as lamellar crystals with monoclinic structure. The fact that the peroxide group is exchanged for the hydrogen of the tertiary carbon demonstrates the high activity of the latter and gives strong support for its involvement in the self-protonation mechanism proposed earlier for the poly(4-vinylpyridine)/pyridine gel.

Effect of Geometrical Confinement on the Nucleation and Crystallization Behavior of n-Alkane Mixtures

The condensed structure of normal alkane (n-alkane) mixtures in confined geometry is an interesting topic concerning the difference in crystallization behavior of odd and even alkanes. In the present work, the crystallization of mixtures of normal octadecane (n-C18H38) and normal nonadecane (n-C19H40) in microcapsules with narrow size distribution was investigated using the combination of differential scanning calorimetry (DSC) and X-ray diffraction (XRD). A surface freezing monolayer for microencapsulated n-C18H38, n-C19H40, and their mixture was detected by DSC, which for the mixture is a mixed homogeneous crystalline phase with continuous change in the composition. A more stable rotator phase (RI) was observed for the microencapsulated n-C18H38/n-C19H40 = 95/5 (molar ratio) mixture, confirmed by an increased supercooling of the transition from RI to stable phase compared to that of the mixture in bulk. Two nucleation mechanisms were speculated as "liquid-to-solid" heterogeneous nucleation and "solid-to-solid" homogeneous nucleation, which occur at different crystallization stages in microcapsules and might be attributed to the surface effect and confinement effect, respectively, in the confined geometry.