Mixture Of PS Research Articles

1,2-Dioleoylglycerol promotes calcium-induced fusion in phospholipid vesicles

The effect of 1,2-dioleoyglycerol (1,2-DOG) on the promotion of Ca 2+-induced fusion of phosphatidylserine/phosphatidylcholine (PS/PC) vesicles was studied. 1,2-DOG is able to induce the mixing of membrane lipids at concentrations of 10 mol% without mixing of vesicular contents. At concentrations of 20 mol% or higher, 1,2-DOG promotes fusion, lipid and content mixing of LUV composed of an equimolar mixture of PS and PC, which otherwise are unable to fuse in the presence of Ca 2+. Fusion was demonstrated by fluorescence assays monitoring mixing of aqueous vesicular contents and mixing of membrane lipids. Studies by Fourier transform infrared spectroscopy provided evidence for a fusion mechanism different to that of Ca 2+-induced fusion of pure PS vesicles. Final equilibrium structures were characterized by 31P-NMR and freeze-fracture electron microscopy. Ca 2+-induced fusion of 1,2-DOG containing vesicles is accompanied by the formation of isotropic structures which are shown to correspond to structures with lipidic particle morphology. The possible fusion mechanisms and implications are discussed.

Diffusion of PS in PS-PVME Mixtures

Viscoelastic and forced Rayleigh scattering measurements were made on mixtures of PS and PVME over the wide range of temperature and PS molecular weight. The temperature dependence of the tracer diffusion coefficient D of PS in PVME was well described by the shift factor aT obtained from time‐temperature superposition of the dynamic shear modulus data of PVME in bulk. The dependence of D on PS molecular weight was described by the free‐draining Rouse chain model in the low M region where the coil size of the diffusing PS chain is smaller than the mesh size of the PVME entanglement network. In the high M region, on the other hand, D did not decrease in proportion to M−2, being in disagreement with the prediction of the reptation model, but took a constant value nearly equal to the calculated Ds value of the PVME molecule in bulk at the high M end. Two conjectures were proposed for interpretation of the above anomalous diffusion behavior.

Free calcium and calpain I activity

Activation of purified calpain I proceeds through a Ca(2+)-induced autolysis from the 80 kDa catalytic subunit to a 76 kDa form via an intermediate 78 kDa form, and from a 30 kDa form to a 18 kDa form as the result of two autocatalytic processes (intra and intermolecular). The minimum Ca2+ requirements for autolysis and proteolysis have been determined by physico-chemical and electrophoretic methods in the presence or absence of a digestible substrate. According to our results the activation process needs less free Ca2+ than the proteolysis of a digestible substrate, which means that proteolysis is really subsequent to activation. For very low Ca2+ levels, a digestible substrate does not initiate the calpain I activation process. In the presence of phospholipid vesicles, such as PI, PS or a mixture of PI (20%), PS (20%) and PC (60%), the apparent kinetic constants of activation are greatly increased without any change in the initial velocity of the substrate proteolysis. Thus, enzyme activation and substrate proteolysis are observed as independent phenomena. These results obtained from experiments using low free Ca2+ concentrations enable us to propose a hypothesis for the mechanism of regulation by which the enzyme could be activated in the living cell.

Dynamics of polystyrene/poly(vinyl methyl ether) blends

Diffusion and viscosity measurements were performed on compatible mixtures of PS and PVME. Elastic recoil detection studies show that the diffusion coefficient, D G , of deuterated polystyrene (PS-d) chains into highly entangled mixtures of PS/PVME is well described by D G ∼M −2 , where M is the molecular weight of the PS-d chains. Under conditions of T-T g =100°C, where T g is the glass transition temperature of the blend, the composition dependence of the friction factor of the PS-d chains exhibited a very large positive deviation from predictions made by the rule of additivity

Partial purification of the Acyl-CoA elongase of Allium porrum leaves

Acyl-CoA elongase has been partially purified from leek ( Allium porrum L.) epidermal cells. The microsomal elongase is first solubilized by Triton X-100. The solubilized proteins are then submitted to anion exchange chromatography on DEAE-cellulose and, finally, to gel filtration on Ultrogel 34 AcA. The purification of the elongase activity is accompanied by the enrichment in three major protein bands of 59, 61, and 65 kDa. The partially purified elongase is highly delipidated (about 10 mol lipid/mol of 60- to 65-kDa protein) and phosphatidylserine and phosphatidylethanolamine account respectively for 60 and 40% of the remaining phospholipids. The partially purified elongase retains some activities associated with fatty acid biosynthesis. The overall activity is strongly stimulated by the addition of exogenous lipids. In the presence of a mixture of PS, PE, and PC the C 18-CoA elongase activity is increased more than sixfold. The K m value of stearoyl-CoA, in the presence of lipid vesicles, was determined to be 1.7 μ m.

Attenuation and envelope formation of three‐component seismograms of small local earthquakes in randomly inhomogeneous lithosphere

A unified model is proposed for explaining the frequency dependence of Q−1 and the formation of velocity seismograms by a single scattering process. Adopting Birch's law and a linear correlation between P and S wave velocities, we statistically describe the inhomogeneous medium by one random fluctuation, which is spatially characterized by the exponential autocorrelation function. We calculate Q−1 for P and S waves on the basis of the Born approximation, supposing seismic waves attenuate due to scattering largely by rapidly fluctuating random structure. Resulting Qs−1 explains the observed frequency dependence well, when the mean square fractional fluctuation and the correlation distance are chosen to be 0.01 and 2 km, respectively. Nonspherical radiation due to a point shear dislocation and frequency dependent nonisotropic scattering including conversion between P and S waves complicate the seismograms. Taking those complexities into account, we synthesize the “envelopes” of three‐component velocity amplitudes of P and S coda waves by summing up energy singly scattered by distributed inhomogeneities. From numerical calculations, we found that the radial component of the P coda wave is excited even in the nodal direction of the P wave radiation mostly due to SP scattering occurring near the hypocenter. The P coda waves appearing on the transverse components are a complex mixture of PP, PS, and SP scattering. The S coda waves are excited mostly due to SS scattering in all directions, and appear in all three components; their polarizations are controlled by the radiation pattern even in the later part of S coda waves.

Visco-elastic dynamic characteristics of polystyrene modified using butadiene-styrene block-copolymers

Visco-elastic dynamic characteristics of melts of PS mixtures and three-block butadiene-styrene copolymers (type SBS) were studied in a wide range of frequencies and temperatures. The introduction of SBS additives into PS has an alloying action, the optimum of which is achieved with a content of SBS of ≈10 wt.%. Results of dynamic investigations and electron microscopy prove that the copolymer separates into an independent phase. The possibility was considered of evaluating heterophase properties of the polymer composition by comparing the dependences of viscosity on shear rate and of composite dynamic viscosity on frequency.

Studies on the optimal conditions of CSF generation by endotoxic LPS and its PS derivative in mice.

Not only the endotoxic LPS preparations, but a non-toxic, lipid-free, non-mitogenic hydrolytic breakdown product of it (called PS) is also capable of inducing colony stimulating factor (CSF) release (1). Due to difficulties to reproduce above findings it became necessary to study the optimal conditions to obtain CSF active PS preparations. It was found that the CSF generating component of the highly heterogeneous PS mixture is sensitive to acidic hydrolyses, but it is less sensitive than the toxic site in the lipid moiety of the LPS. Carefully controlled optimal hydrolytic conditions give PS preparations which have less than one percent residual endotoxicity but maintained 40 to 80% of the original CSF generating capacity. Prolonged hydrolysis will destroy this activity too. Optimal dose of LPS and PS for CSF induction in mice differed widely. For LPS the optimal dose is 25 micrograms, injecting more gave a much reduced or non-detectable CSF level. Optimal dose for PS was 160 micrograms, and this generated a significantly higher CSF level than 25 micrograms LPS. At concentrations below 25 micrograms, LPS was clearly more active than PS. The CSF level reached its peak at 3-4 hours after other LPS or PS injection. Intravenous route was sometimes but not always more effective than intraperitoneal.

Influence of molecular weight and molecular conformation of polymers on turbulent drag reduction

An investigation was carried out on drag reduction of diluted solutions of four polyisobutylenes of different molecular weight in diversely good and poor solvents in the turbulent region at small (up to 5000) and average (from 19 000 to 42 000) Reynolds numbers, as well as of mixtures of polyisobutylene and polystyrene and of two polyisobutylenes of different molecular weight. Concentration at maximum drag reduction grows, while drag reduction itself decreases with molecular weight going down. The universal curve established byVirk et al. for aqueous solutions of a polyethylene oxide family is also confirmed for a family of polyisobutylenes in an organic solvent. The effect of polymer coils of various dimensions on drag reduction is assessed. PIB coils of various dimensions are produced in two ways — dissolving polyisobutylenes of different molecular weight in a given solvent and dissolving polyisobutylene of a definite molecular weight in diversely good and poor solvent. Coil dimensions in the solution are increasing with the growth of intrinsic viscosity of a polymer by dissolving it in still better solvents, but probably due to impeded orientation and deformation of the larger polymer coils their drag reduction is smaller at low rather than at high shear stresses. Drag reduction of diluted solutions of two PIB differing in molecular weight shows almost no deviation from the additive straight line both when the overall concentration of solutions is equal and when it exceeds the one at maximum drag reduction of PIB of higher molecular weight. Drag reduction of diluted solutions of PIB and PS mixtures at an overall concentration higher than optimum concentration shows a positive deviation from the additive straight line.

Preparation of amphipathic block copolymers of styrene and vinyl acetate by a free radical mechanism and saponification of the products

Block copolymers of styrene and vinyl acetate (VA) of different composition have been prepared by a free mechanism in the presence of triperoxide. Block copolymers of styrene and vinyl alcohol (VAl) were obtained by saponification of the styrene-VA copolymers. The fact that block copolymers are formed is shown by the increase in [η], the infrared spectra and by comparison of turbidimetric curves of a styrene-VA block copolymer and of a mixture of PS and PVA.

High-performance gel permeation chromatography with a new type of silica packing material

Highly poroas silica beads in the 10-μm size range with graduated pore sizes were tested as packings for the separation of polystyrene standards. As a result of the high internal porosity of the packings, relatively large capacity factors of the solutes and selectivity factors up to 4.0 were achieved. On 25-cm columns at u0.1 cm sec the following numbers of theoretical plates were obtained: for ethylbenzene, 4000: for PS 5, 1000: and for PS 411, 400. For all columns, the plot of log M w versus N 12 gave a linear relationship. The selectivity and column efficiency were demonstrated by separating a mixture of PS 411, PS 98, PS 51, PS 19, PS 5 and PS 2 at a flow-rate of 0.1 ml min in 45 min on a 25-cm column.

Factors Influencing the Consumption of Factor X (Stuart-Prower Factor) during Intrinsic Coagulation

Summary1. Factor X is consumed during in vitro intrinsic coagulation of normal blood when both surface activation and either bovine AHG or phospholipid such as cephalin, hemolysate, PS, PE, or mixture of PS and PE are present. Neither surface activation, AHG or phospholipid alone produces significant consumption of factor X.2. Consumption of factor X did not occur in hemophilic bloods (AHG or PTC deficient) when both surface activation and phospholipid were present.3. The consumption of factor X in blood from human subjects, with high factor VIII levels, when surface activation was provided, was only moderately augmented compared with results in blood with a normal factor VIII level.4. The consumption of factor X in the blood of a patient with a SLE inhibitor was similar to that in normal blood when both contact activation and phospholipids were supplied.

Bacterial Synthesis of Nucleotides

The optimal pH of the phosphoryl transfer reaction between nucleotide and nucleoside was found to be not always the same. In the reaction mixture of Ps. trifolii, the optimal pH of its activity was at around 8.5, and 5'-nucleotide was the most excellent donor. Phophotransferase activity of Prot. mirabilis had an optimal pH at around 5.0, and 2'- and 3'-nucleotide were observed to just make a donor. These donor- and product-isomer specificities of both groups of bacteria were evident to be invariable, regardless of reaction pH and the cultural conditions of each bacterium, and, therefore, are considered to be attributed to their substantial characters. The fact that the phosphoryl transfer reaction between purine nucleosides and pyrimidine nucleotides was reversible suggests that this enzymatic activity may catalyze the phos-phoryl interconversion of 5'-nucleotides in these bacterial cells of A group. Cupric ions and arsenate were observed to stimulate the synthesis of nucleotide.

METABOLISM OF AROMATIC COMPOUNDS BY BACTERIA,

1. m-Hydroxybenzoic acid hydroxylase A which catalizes m-hydroxybenzoic acid to potocatechuic acid was obtained as cell-free enzyme from the cells of Ps. dacunhae A-7-2 and R-10-2 and m-hydroxybenzoic acid hydroxylase B which catalyzes m-Hydroxybenzoic acid to gentisic acid was obtained from the cells of Ps. sp. 15-1A and strain 23-1A, 42-1A. Each enzyme requires TPN, probably TPNH, as a cofactor.2. The constitutive enzymatic pathway via protocatechuic acid in the cells of Ps. ovalis S-5, was demonstrated, and its activity is strongest at the stationary phase during the growth of the cells. Shikimic acid is converted to protocatechuic acid by the incubation with the cells and this pathway is not inhibited by the addition of streptomycin 10-3M.3. From the incubation mixture of Ps. ovalis S-5 with shikimic acid, 5-dehydroshikimic acid was crystallized which is produced from shikimic acid and converted to protocatechuic acid. Thus, 5-dehydroshikimic acid was recognized as a precursor to protocatechuic acid.4. The pathway from m-hydroxybenzoic acid was examined among the one hundred and thirtythree strains isolated from the soil and sewages. It was concluded that one hundred and nine strains had protocatechuic acid path. And a new pathway from salicylic acid to gentisic acid was recognized in the cells of Ps. sp. 15-1A, 15-4A and 40-2A.

METABOLISM OF AROMATIC COMPOUNDS BY BACTERIA,

1. m-Hydroxybenzoic acid hydroxylase A which catalizes m-hydroxybenzoic acid to potocatechuic acid was obtained as cell-free enzyme from the cells of Ps. dacunhae A-7-2 and R-10-2 and m-hydroxybenzoic acid hydroxylase B which catalyzes m-Hydroxybenzoic acid to gentisic acid was obtained from the cells of Ps. sp. 15-1A and strain 23-1A, 42-1A. Each enzyme requires TPN, probably TPNH, as a cofactor.2. The constitutive enzymatic pathway via protocatechuic acid in the cells of Ps. ovalis S-5, was demonstrated, and its activity is strongest at the stationary phase during the growth of the cells. Shikimic acid is converted to protocatechuic acid by the incubation with the cells and this pathway is not inhibited by the addition of streptomycin 10-3M.3. From the incubation mixture of Ps. ovalis S-5 with shikimic acid, 5-dehydroshikimic acid was crystallized which is produced from shikimic acid and converted to protocatechuic acid. Thus, 5-dehydroshikimic acid was recognized as a precursor to protocatechuic acid.4. The pathway from m-hydroxybenzoic acid was examined among the one hundred and thirtythree strains isolated from the soil and sewages. It was concluded that one hundred and nine strains had protocatechuic acid path. And a new pathway from salicylic acid to gentisic acid was recognized in the cells of Ps. sp. 15-1A, 15-4A and 40-2A.