Synthesis and properties of NiSn colloids using different metal ratios by CLD

Bimetallic colloidal dispersions of Ni–Sn were prepared by simultaneous co-condensation with organic solvents at 77 K using the chemical liquid deposition (CLD) method. The atoms in a 1:1, 2:1, 3:1, 1:2 and 1:3 ratios were produced by resistive heating and were reacted with 2-propanol, 2-methoxyethanol, ethanol and acetone to produce colloids. The bimetallic films and solids were obtained by evaporation under vacuum at room temperature. The colloids and solids were characterized by several studies, including the stability at room temperature, electrophoresis, ultraviolet-visible spectrophotometry, transmission electron microscopy (TEM), electron diffraction, conductivity, nergy dispersive X-ray analysis, electrophoretic measurements, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and magnetic properties. TEM studies show a size distribution between 6 and 14 nm, depending of the solvent and Ni:Sn ratio. We can observe a high stability for the colloidal dispersion with different solvents (>2 weeks); this is due mainly to the solvation capacity and polarity of the organic molecules. Electrophoretic measurements revealed that the particles are weakly positively charged with a greater Ni percentage. Electron diffraction analysis for the metallic colloids shows the presence of bimetallic compounds as NiSn, Ni₃Sn, Ni₃Sn₄ and tin oxides. XPS analysis was used for the study of the Ni–Sn solid composition, where it was determined that the Ni atoms could be as Ni⁰ and Ni²⁺. The bond energy difference in both species were 0.8 eV; on the other side, Sn atoms showed two peaks, the first associated with Sn⁰ atoms and the second attributed to oxidized species like SnO_x. The conductivity studies showed that when the metal is changed, the electric conductivity properties change too and are associated with the particle size increasing.     

Insertion of tear proteins into a meibomian lipids film

The eyelid meibomian gland secretions form the outer layer of the tear film. That layer functions as a lubricant during a blink, and as a barrier against intrusion of foreign bodies. The lipid film is also exposed to proteins present in the aqueous phase that may adsorb there, and thus form an integral part of the surface of the tear film, or possibly, cause disruption to the outermost layer. Therefore, the adsorption of tear proteins to the meibomian lipid layer was object of the present investigation. A model tear was set up coating a pendant drop of saline with a film of meibomian lipids and measuring variations of the interfacial pressure after the injection of tear proteins into the aqueous subphase at their physiological concentration. All tear proteins adsorbed at the interface causing the initial surface pressure to increase. For each protein, a limiting surface pressure at which a given protein was no longer able to insert into the lipid layer was found. Among the proteins tested, lipocalin was the most surface active one and inserted into the lipid layer in the whole range of surface pressure exerted by the meibomian lipid mixture. Lactoferrin, lysozyme and IgA also interacted with the lipids whereas albumin interacted more weakly. The timescale of the protein insertion into the lipid layer was of the order of 10(2) s. It was hypothesized that protein adsorption at the interface could be associated with structural changes. Indeed, the enzymatic activity of lysozyme was maintained in the presence of an outermost meibomian lipid layer that prevented its denaturation while exposure at the air/aqueous interface induced significant lysozime degradation. meibomian lipid composition is therefore functional to maintain tear proteins activity.     

Theoretical evaluation of atomic charges to be integrated into conformational analyses of neutral lipids

Conformational analyses of large molecules as fatty acids and triglycerides are usually amenable by molecular mechanics. A correct evaluation of the electrostatic energy term is thus crucial in determining reliable results. In this contribution, we have considered the most abundant fatty acids in biomembranes, i.e., lauric, stearic, oleic, and elaidic acid, and the corresponding triglycerides, i.e., trilaurin, tristearin, triolein, and trielaidin, and estimated the Mulliken and potential-derived charges both at the semiempirical AM 1 and ab initio HF MO STO -3G level. Atomic charges obtained by the Mulliken population analysis do not take into account the full geometry of the molecule. On the contrary, the change of conformation, due to different chains length or the presence of a trans or cis double bond, greatly influences the repartition of the potential-derived charges. A systematic comparative analysis shows that charges calculated by AM 1 are not suitable because as they do not reproduce potential-derived charges obtained by ab initio. © 1993 John Wiley & Sons, Inc.     

Copolymerization of a dendronized monomer with styrene and different acrylates: Determination of reactivity ratios

The reactivity ratios for the copolymerization of a first‐generation dendronized monomer with styrene and different acrylates are determined. The obtained ratios as well as the copolymer compositions that can be expected are discussed in detail. The influence of the dendron on the polymerization potential of the monomer is estimated by comparing its reactivity to those of linear systems as well as using higher generations of the dendronized monomer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Rapid screening of phenylketonuria using a CD microfluidic device

We herein present a compact disc (CD) microfluidic chip based hybridization assay for phenylketonuria (PKU) screening. This CD chip is composed of a polydimethylsiloxane (PDMS) top layer containing 12 DNA hybridization microchannels, and a glass bottom layer with hydrogel pad conjugated DNA oligonucleotides. Reciprocating flow was generated on the CD chip through a simple rotation-pause operation to facilitate rapid DNA hybridization. When rotated the CD chip, the sample solution was driven into the hybridization channel by centrifugal force. When stopped the CD chip, the sample plug was pulled backward through the channel by capillary force. The hybridization assay was firstly validated with control samples and was then used to analyze 30 clinical samples from pregnant women with suspected PKU fetus. The on-chip DNA hybridization was completed in 15 min with a sample consumption as low as 1.5μL, and the limit-of-detection (LOD) of DNA template was 0.7ng/μL. Among the 30 samples tested, V245V mutation was identified in 4 cases while R243Q mutation was detected in one case. Results of the hybridization assay were confirmed by DNA sequencing. This CD-chip based hybridization assay features short analysis time, simple operation and low cost, thus has the potential to serve as the tool for PKU screening.     

Targeted Histone Peptides: Insights into the Spatial Regulation of the Methyltransferase PRC2 by using a Surrogate of Heterotypic Chromatin

Eukaryotic genomes are dynamically regulated through a host of epigenetic stimuli. The substrate for these epigenetic transactions, chromatin, is a polymer of nucleosome building blocks. In native chromatin, each nucleosome can differ from its neighbors as a result of covalent modifications to both the DNA and the histone packaging proteins. The heterotypic nature of chromatin presents a formidable obstacle to biochemical studies seeking to understand the role of context on epigenetic regulation. A chemical approach to the production of heterotypic chromatin that can be used in such studies is introduced. This method involves the attachment of a user‐defined modified histone peptide to a designated nucleosome within the polymer by using a peptide nucleic acid (PNA) targeting compound. This strategy was applied to dissect the effect of chromatin context on the activity of the histone methyltransferase PRC2. The results show that PRC2 can be stimulated to produce histone H3 methylation from a defined nucleation site.     

Activation of B cells using Schneider 2 cells expressing CD40 ligand for the enhancement of antigen presentation in vitro

CD40 ligand (CD40L) expressed by activated CD4+ T cells is a family member of membrane bound TNF family ligand and its interaction with CD40 expressed in APC has been shown to contribute in enhancing immune response. Exogenous stimulation through CD40 has been performed using soluble trimeric CD40L, anti-CD40 monoclonal antibody and cells expressing CD40L. Schneider 2 (S2) cells, a cell line derived from Drosophila melanogaster, was transfected with a plasmid vector, pAc5.1/V5-HisA, for the constitutive expression of CD40L (S2-CD40L). Upon incubation of S2-CD40L with B-lymphocytes for 6 days, activated B cells were examined by counting B cell numbers and for activation markers including CD86 and HLA Class II molecules. The activated B cells were tested for its efficient APC function by mixed lymphocyte reactions (MLR) and enzyme-linked Immunospot (ELISPOT) assay. S2-CD40L was cultured for a year and maintained CD40L expression (>90%). S2-CD40L induced B cell activation as demonstrated by increment of total B cells and up-regulation of CD86 and MHC Class II molecules. Activated B cells pulsed with peptide from human cytomegalovirus pp65 antigen efficiently induced both proliferation and IFN-gamma secretion of T cells. Our result suggests that S2-CD40L can efficiently and conveniently generate B cells as a functional APC and represents a potential role for B-cell mediated cancer immunotherapy.     

Development of a chemical vapor sensor using piezoelectric quartz crystals with coated unusual lipids

Piezoelectric quartz crystal sensors were developed using lipids with various properties for highly sensitive detection of chemical vapors. Lipids with varying lengths of alkyl chains were coated onto 10 MHz AT-cut quartz crystal resonators and the response of these modified crystals to chemical vapors were measured. It was shown that hydrophilic compounds, such as ethanol and methanol, could be recognized efficiently by lipids having shorter alkyl chains, whereas lipids with longer alkyl chains showed affinity to more hydrophobic vapors, such as toluene, hexane and cyclohexane. Frequency changes caused by adsorption of alcohols could be enhanced when cholesterol was co-immobilized in the lipid layer. To confirm the assumption that the sensor-response might be affected by the properties of lipids derived from acyl chains, we have examined the effects of two types of newly synthesized unusual lipids on sensor response. When lipids having one triple bond each at different positions on their alkyl chains were coated onto quartz crystals separately, lower responses were observed compared to responses obtained for a sensor with immobilized, saturated phosphatidylcholine. Lipids containing -branched acyl chains, however, showed good affinity for organic vapors, and sensor responses improved 4–5-fold. Moreover, these sensors were shown to have sensitivity of the same order as the humans' sense of smell (10⁻⁵–10⁻⁶ w/w in liquid paraffin) when measured using standard odorants (isovaleric acid, skatole, etc.) for an olfactometry established in Japan.     

The flame height of rectangular pool fires bounded by a sidewall with different distances and aspect ratios

Journal of Thermal Analysis and Calorimetry - This paper presents an investigation on the flame height of rectangular pool fires bounded by a sidewall. A series of experiments were conducted to...     

Ozone-induced dissociation on a modified tandem linear ion-trap: Observations of different reactivity for isomeric lipids

Ozone-induced dissociation (OzID) exploits the gas-phase reaction between mass-selected lipid ions and ozone vapor to determine the position(s) of unsaturation. In this contribution, we describe the modification of a tandem linear ion-trap mass spectrometer specifically for OzID analyses wherein ozone vapor is supplied to the collision cell. This instrumental configuration provides spatial separation between mass-selection, the ozonolysis reaction, and mass-analysis steps in the OzID process and thus delivers significant enhancements in speed and sensitivity (ca. 30-fold). These improvements allow spectra revealing the double-bond position(s) within unsaturated lipids to be acquired within 1 s: significantly enhancing the utility of OzID in high-throughput lipidomic protocols. The stable ozone concentration afforded by this modified instrument also allows direct comparison of relative reactivity of isomeric lipids and reveals reactivity trends related to (1) double-bond position, (2) substitution position on the glycerol backbone, and (3) stereochemistry. For cis- and trans-isomers, differences were also observed in the branching ratio of product ions arising from the gas-phase ozonolysis reaction, suggesting that relative ion abundances could be exploited as markers for double-bond geometry. Additional activation energy applied to mass-selected lipid ions during injection into the collision cell (with ozone present) was found to yield spectra containing both OzID and classical-CID fragment ions. This combination CID-OzID acquisition on an ostensibly simple monounsaturated phosphatidylcholine within a cow brain lipid extract provided evidence for up to four structurally distinct phospholipids differing in both double-bond position and sn-substitution.     

Simultaneous determination of drugs in concentration ratios above 40:1 by application of multivariate calibration to absorbance and derivative spectrophotometric signals

The performance of two multivariate calibration methods, multiple linear regression (MULTI3) and partial least-square regression (PLS-2), for the resolution of the ternary mixtures of acetylsalicylic acid-caffeine-codeine and acetaminophen-caffeine-codeine is compared. The methodologies were checked by applying them to the analysis of two sets of laboratory-prepared mixtures over the concentration ranges 13.0–19.0, 1.00–3.00 and 0.20–1.00 μg · ml^–1 for acetylsalicylic acid-caffeine-codeine and 12.0–22.0, 0.40–2.00 and 0.20–1.00 μg · ml^–1 for acetamimophen-caffeine-codeine, respectively. While the results provided by MULTI3 were unacceptable in the majority of the cases, those obtained by PLS-2 were quite good with considerably diminished errors, as a result of calibration and/or checking with MULTI3, taking no account of potential interactions between analytes. It was shown that it is possible by using PLS-2 to resolve complex mixtures of analytes in a highly disparate proportion, even when they have overlapping signals. The proposed method was successfully demonstrated for pharmaceutical tablets. Received: 7 February 1996 / Revised: 22 April 1996 / Accepted: 28 April 1996     

Demonstration of a convergent approach to UV-polymerizable lipids bisDenPC and bisSorbPC

Lipids containing UV-polymerizable diene moieties, such as BisDenPC 1 and BisSorbPC 2, have been extremely useful for the construction of micelles and lipid bilayers. The published syntheses have yielded lipids with only a trimethylamine head group. We have improved the syntheses of these monomers by a convergent method employing the Chabrier reaction of trimethylamine with a cyclic phospholane. This method can be extended to a variety of dialkylamine derivatives.     

Isolation of the alanine carrier from the membranes of a thermophilic bacterium and its reconstitution into vesicles capable of transport.

A carrier protein mediating alanine transport was purified from the membranes of the thermophilic bacterium PS3, by ion exchange chromatography in the presence of both Triton X-100 and urea. The alanine carrier was recovered in the nonadsorbed fraction from either DEAE- or CM-cellulose columns, suggesting that its isoelectric point was in the neutral pH region. The final preparation contained virtually no electron transfer components, ATPase, or NADH dehydrogenase. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate revealed that the final preparation consisted of two major protein components with molecular weights of 36,000 and 9,400. Active transport of alanine after incorporation of the alanine carrier into reconstituted proteoliposomes was driven not only by an artificial membrane potential generated by potassium ion diffusion via valinomycin but also by mitochondrial cytochrome oxidase incorporated into the same liposomes and supplemented with both cytochrome c and ascorbic acid. The membrane-integrated portion (TFo) of the ATPase complex uncoupled alanine transport by conducting protons across the membrane.     

Preparation,characterization and in vitro antitumoral activity of a nanosize liposome complex encapsulated polyoxotungstate K6H2[CoW11TiO40]

The nanosize liposome complex-encapsulated polyoxotungstate K₆H₂[CoW₁₁TiO₄₀] has been prepared and structurally characterized by i.r., u.v.–vis and e.s.r. spectra. The particle size of the liposome complex-encapsulated K₆H₂[CoW₁₁TiO₄₀], is distributed in two uncontinuous limits in which 98.9% of particles distributed in the limit of 62.8–76.7 nm, average diameter, is 69.4 nm. The result shows that the polyoxotungstate retains the parent structure after being encapsulated by liposome, and that liposomal encapsulation increase the antitumoral activity of the polyoxometalate.     

Fluorescence studies of hydrophobically-modified poly(N-isopropylacrylamides) or how to play accordion on a liposome

The coil/globule transition of polymers in solution is a favourite topic of discussion among polymer theoreticians. Here, this phenomenon is used to play a “molecular accordion” built with a thermosensitive polymer anchored to liposomes, a tune which mimics a natural process occuring in cell membranes.     

Stable carbon isotope ratios of methyl-branched fatty acids are different to those of straight-chain fatty acids in dairy products

Methyl-branched fatty acids (MBFAs) are the dominant form of fatty acid found in many bacteria. They are also found at low levels in a range of foodstuffs, where their presence has been linked to bacterial sources. In this study we evaluated the potential of compound-specific isotope analysis to obtain insights into the stable carbon isotope ratios (δ¹³C values in ‰) of individual MBFAs and to compare them to the stable carbon isotope ratios of straight-chain fatty acids in food. Due to their low abundance in foodstuffs, the MBFAs were enriched prior to gas chromatography coupled to isotope ratio mass spectrometric (GC–IRMS) analysis. After transesterification, urea complexation was used to suppress the 16:0 and 18:0 methyl esters that were dominant in the samples. Following that, silver-ion high performance liquid chromatography was used to separate the saturated from the unsaturated fatty acids. The resulting solutions of saturated fatty acids obtained from suet, goat’s milk, butter, and human milk were studied by GC–IRMS. The δ¹³C values of fatty acids with 12–17 carbons ranged from −25.4‰ to −37.6‰. In all samples, MBFAs were most depleted in carbon-13, followed by the odd-chain fatty acids 15:0 and 17:0. 14:0 and 16:0 contained the highest proportions of carbon-13. The results from this study illustrate that MBFAs have distinctive δ¹³C values and must originate from other sources and/or from very different substrates. These measurements support the initial hypothesis that δ¹³C values can be used to attribute MBFAs to particular sources.     

Fluorescence response of hypocrellin B to the environmental changes in a mimic biological membrane—liposome

Liposome is well known as not only a drug-delivery system but also a simple model for biological membranes. It was reported that fluorescence properties of hypocrellins were changeable over some extreme pH values. In the current work, the effects of the microenvironments on the fluorescence properties of HB in liposome, including approximately physiological range of pH values pH = 6.0-8.0, concentration of cholesterols and ionic strength of the solution, were studied. It was found that the fluorescence intensity of HB was sensitive to and also regulated by the microenvironments. When concentration of cholesterols and ionic strength keep invariable in PBS solution, there exists the maximum for the fluorescence of HB-liposome at pH 7.4 while the minimum for that of HB at pH 7.0. In addition, when pH value keeps constant (7.2), there exists the maximum at the ionic strength of 0.12 mol/kg while that at the concentration of 6×10^?4 mol/L for cholesterols. On the other hand, in PBS solution, the lower the ionic strength is, the higher the fluorescence intensity is. The environment-sensitive fluorescence may be potentially applicable to probe some specific environmental features in cells or tissues.

     

Incorporation of quantum dots into a silica matrix using a compatible precursor

A method is developed for one-stage incorporation of cadmium-sulfide quantum dots synthesized in the presence of mercaptosuccinic acid into a silica matrix formed from a precursor containing ethylene-glycol residues—tetrakis(2-hydroxyethyl) orthosilica. This precursor has not previously been applied for this purpose. It is more compatible with diverse substances than tetraethoxysilane, which is traditionally used. Moreover, it is advantageous in its unlimited solubility in water; release of ethylene glycol, which does not precipitate quantum dots, rather than alcohol upon hydrolysis; and the feasibility of performing the sol-gel process at any pH value in a range of 2–10 without the addition of acid or alkali and without heating. When the precursor (50 wt %) is added to a dispersion of quantum dots, the system is transformed into a gel in as little as a few minutes. The synthesized hybrid materials are optically transparent. Therewith, the quantum dots incorporated into the silica matrix exhibit luminescence, with their spectral characteristics remaining almost unchanged.