Iota-carrageenan/casein micelles interactions: evidence at different scales

The effect of temperature on the behaviour of iota-carrageenan (CI) 0.1 wt.%/casein micelles (CM) 0–5 wt.% mixtures has been studied using three techniques: confocal laser scanning microscopy (CLSM), differential scanning calorimetry (DSC) and spectrophotometry. The microscopy clearly shows that those mixed systems separate in two phases, one being enriched in CM. It has been shown that the CM concentration seems to have an effect on the extent of the phase separation phenomenon. The DSC experiments show that addition of CM modifies the helix to coil transition temperature of carrageenan. The enthalpy of melting of helices decreases as the CM concentration increases, and the peak is shifted towards higher temperature. Local electrostatic interactions between carrageenan chains and CM have been studied by a spectrophotometric method using methylene blue (MB) properties of absorption. The absorption spectra of MB in presence of CI and CM were compared with the one of MB in presence of carrageenan alone at temperatures above and below the carrageenan coil to helix transition. The modifications of the spectrum by addition of CM are discussed in terms of interactions and rigidification of the carrageenan chains.     

Physicochemical and catalytic characterizations of materials prepared from copper malonate by thermal decomposition or chemical reduction

Results of Carr and Galwey [1] concerning copper malonate (CM) decomposition in vacuo at 510 K prompted present studies on the utility of CM as a low-temperature precursor of oxide-supported copper catalysts. CM deposited upon metal oxides has been converted to copper particles by vacuum thermal decomposition or reduction with aqueous hydrazine. Using the dehydrogenation of isopropanol to acetone as a catalytic probe reaction, comparisons are made between levels of catalytic activity and selectivity induced in TiO₂, MgO and Ca(OH)₂ supports by copper deposited thereon. Effects of particle size, prereduction temperature, and support reducibility are described and evidence is given for a strong metal support interaction (SMSI)-like inhibition of activity of Cu/TiO₂ by prior high temperature reduction.     

Thermodynamic Parameters of Cholesteric/Smectic A Transition in Cholesteric Myristate and Its Binary Mixture CM/PCPB

Thermodynamic properties of the cholesteryl myristate (CM) and its binary mixture CM/PCPB (p-pentylphenyl-2-chloro-4(p-pentylbenzoyl)-benzoate) are studied at the concentrations of x_PCPB = 0.052 and 0.219 as a function of temperature near the cholosteric/smectic A transition. By analyzing the observed molar volume from the literature, the temperature dependences of the thermal expansion, isothermal compressibility and the difference in the specific heat are calculated and, the Pippard relations are established for those compounds close to the cholesteric/smectic A transition. Predictions of the thermodynamic quantities and the Pippard relations can be examined by the experimental measurements of the CM and its binary mixture of CM/PCPB close to the cholesteric/smectic A transition.     

钼酸根阴离子印迹陶瓷膜的制备与吸附性能

以三氧化二铝陶瓷膜为载体,以钼酸根阴离子为模板离子,1-乙烯基咪唑为功能单体,1,6-二溴己烷为交联剂,采用表面印迹和接枝聚合方法制备了能选择性吸附Mo(Ⅵ)的新型印迹陶瓷膜(IIP-PVI/CM).采用红外光谱、X射线光电子能谱、热重分析及扫描电子显微镜等方法对陶瓷膜进行结构表征.研究了pH值对吸附性能的影响,当pH值范围为2~4时,IIP-PVI/CM具有良好吸附能力;动力学和热力学结果表明,IIP-PVI/CM对Mo(Ⅵ)的吸附符合准二级动力学模型和Langmuir吸附模型;当pH=4.0和温度为30℃时,IIP-PVI/CM对Mo(Ⅵ)具有良好选择性,Mo(Ⅵ)对W(Ⅵ)的选择性系数高达7.48;动态吸附结果表明,IIP-PVI/CM对W(Ⅵ)和Mo(Ⅵ)的吸附饱和时间分别为24和47 min,饱和吸附量分别为0.163和0.672 mmol/100 g,动态吸附时IIP-PVI/CM亦具有良好选择性;经9次吸附与解吸后,IIP-PVI/CM对Mo(Ⅵ)吸附容量仍可达到初始值的92%,再生和循环使用性能良好.     

Synthesis of symmetrical trisubstituted olefins by cross metathesis

[reaction: see text] Trisubstituted alkenes have been prepared via intermolecular olefin cross-metathesis (CM) between alpha-olefins and symmetrically 1,1-disubstituted olefins using an imidazolylidene ruthenium benzylidene complex. Of particular interest is the synthesis of isoprenoid/prenyl groups by a simple solvent-free CM reaction with isobutylene. In addition, prenyl groups can also be installed by a cross-metathesis of 2-methyl-2-butene with a variety of alpha-olefins at room temperature with low catalyst loadings.     

Monitoring the moisture-related degradation of ethylene propylene rubber cable by electrical and SEM methods

Several electrical approaches were used to monitor the electrical degradation of ethylene propylene rubber (EPR) cable under (1) high temperature water submerged for long-term, (2) room temperature water submerged after thermal and radiation aging, and (3) loss-of-coolant accident simulation conditions. The moisture-related degradation behavior was investigated by the correlation of electrical measurements, moisture content analysis, and scanning electron microscope (SEM) observation. The results indicate that void size and density of insulation material strongly affect the material's water resistant capability and electrical degradation. Also, the void size of insulation material after moisture-related degradation is much bigger than that after thermal and radiation aging, and the former causes material swelling. Combining insulation resistance and dissipation factor condition monitoring (CM) techniques can provide useful means for monitoring cable degradation while the cable is exposed to moisture and high temperature/radiation environment. The Arrhenius model is applied together with appropriate acceptance criteria obtained by insulation resistance measurement to calculate cable remaining life. According to test results and the remaining life calculation, it is shown that the moisture-related degradation of EPR cable can be early assessed by insulation resistance measurement, which is a non-destructive prognostic CM technique.     

Solvent interactions and conformational choice in a core N-glycan segment: gas phase conformation of the central, branching trimannose unit and its singly hydrated complex

The intrinsic conformational preferences and structures of the branched trimannoside, alpha-phenyl 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside (which contains the same carbohydrates found in a key subunit of the core pentasaccharide in N-glycans) and its singly hydrated complex, have been investigated in the gas phase isolated at low temperature in a molecular beam expansion. Conformational assignments of their infrared ion dip spectra, based on comparisons between experiment and ONIOM (B3LYP/6-31+G(d):HF/6-31G(d)) and single-point MP2 calculations have identified their preferred structures and relative energies. The unhydrated trimannoside populates a unique structure supported by two strong, central hydrogen bonds linking the central mannose unit (CM), and its two branches (3M and 6M) closely together, through a cooperative hydrogen-bonding network: OH4(CM)-->OH6(3M)-->OH6(6M). A closely bound structure is also retained in the singly hydrated oligosaccharide, with the water molecule bridging across the 3M and 6M branches to provide additional bonding. This structure contrasts sharply with the more open, entropically favored trimannoside structure determined in aqueous solution at 298 K. In principle this structure can be accessed from the isolated trimannoside structure by a simple conformational change, a twist about the alpha(1,3) glycosidic linkage, increasing the dihedral angle psi[C1(3M)-O3(3M)-C3(CM)-C2(CM)] from approximately 74 degrees to approximately 146 degrees to enable accommodation of a water molecule at the centrally bound site occupied by the hydroxymethyl group on the 3M ring and mediation of the water-linked hydrogen-bonded network: OH4(CM) -->OH(W)-->OH6(6M). The creation of a "water pocket" motif localized at the bisecting axis of the trimannoside is strikingly similar to the structure of more complex N-glycans in water, suggesting perhaps a general role for the "bisecting" OH4 group in the central (CM) mannose unit.     

Relaxation dynamics of a linear molecule in a random static medium: a scaling analysis

We present extensive molecular dynamics simulations of the motion of a single linear rigid molecule in a two-dimensional random array of fixed overlapping disklike obstacles. The diffusion constants for the center of mass translation, D(CM), and for rotation, D(R), are calculated for a wide range of the molecular length, L, and the density of obstacles, rho. The obtained results follow a master curve Drho(micro) approximately (L(2)rho)(-nu) with an exponent micro=-3/4 and 1/4 for D(R) and D(CM), respectively, that can be deduced from simple scaling and kinematic arguments. The nontrivial positive exponent nu shows an abrupt crossover at L(2)rho=zeta(1). For D(CM) we find a second crossover at L(2)rho=zeta(2). The values of zeta(1) and zeta(2) correspond to the average minor and major axis of the elliptic holes that characterize the random configuration of the obstacles. A violation of the Stokes-Einstein-Debye relation is observed for L(2)rho>zeta(1), in analogy with the phenomenon of enhanced translational diffusion observed in supercooled liquids close to the glass transition temperature.     

Hierarchical networks of casein proteins: an elasticity study based on atomic force microscopy

2D- and 3D-atomic force microscopy (AFM) experiments were performed on single casein micelles (CM) in native state, submerged in liquid, using a home-built AFM instrument. The micelles were immobilized via carbodiimide chemistry to a self-assembled monolayer supported on gold-coated slides. Off-line data analysis allowed the extraction of both surface topography and elastic properties. Relative Young moduli (E*) were derived from force-vs-indentation curves, using the Hertz theory. The obtained E* values were found to increase with CM diameter, following a straight line dependence. The data showed that temperature, via its influence on both the protein-protein interactions and the composition of the micelle, has a clear effect on the mechanical properties of the CMs: higher temperatures and lower serum casein concentrations result in stiffer micelles. For pH < or = 5.6, effecting calcium phosphate release from the micelles by decreasing the pH does not have a large effect on CM stiffness. On decrease of the pH below 5.0, particulate gels and multilayers were obtained. Their measured elasticity (expressed by an equivalent G'AFM) agrees remarkably well with the storage moduli as measured with a conventional rheometer. Compared to single micelles, gels from nonheated CM suspensions are about 3 orders of magnitude softer. The "softness" of these gels (measured under compression or shear) therefore must come from the microscopic and/or mesoscopic links rather than the micelles themselves.     

Identification and dosimetric features of γ-irradiated cefadroxil by electron spin resonance

In the present work, electron spin resonance (ESR) identification of γ-irradiated cefadroxil monohydrate (CM), duricef capsule (DC) and duricef suspension (DS) and their potential use as normal and/or accidental dosimetric materials were investigated in the dose range of 1–25 kGy. Although unirradiated samples did not exhibit any ESR signals, irradiated samples were observed to present ESR spectra with many resonance lines originating from radiation induced radical or radicals. Dose-response curves associated with the resonance peak heights of CM (I₁, I₂) and DS (I₃, I₄, I₅, I₆) were found to follow linear and power functions of applied radiation dose, respectively. Simulation calculations were performed to determine the structure and spectral parameters of the radiation-induced radicalic species involved in the formation of experimental ESR spectrum of CM using, as input, the room temperature signal intensity data obtained for a sample irradiated at dose of 10 kGy. Kinetic behaviors and activation energies of the radicalic species were also calculated using the data obtained from annealing studies performed at five different temperatures. The presence of detectable signal intensities even after a storage period of 100 days was considered as providing an opportunity in the discrimination of irradiated CM and DS from unirradiated ones. Basing on room temperature signal intensity decay and dose–response data, it was concluded that CM and DS present the features of a good dosimetric material.     

中药红曲化学稳定性多成分综合评价

建立了利用高效液相色谱法同时测定红曲中具降血脂活性的12种他汀类成分的方法, 并进行方法学评价. 研究了红曲在高温(80及60 ℃)高温高湿(60 ℃及75%RH), 室温高湿(25 ℃及92.5%RH)和光照等条件下的化学稳定性, 在40 ℃及75%RH的条件下进行3个月的加速试验. 通过测定稳定性试验样品中12种他汀类成分的含量, 考察了红曲中这些成分的动态变化情况, 并加以综合评价.     

Effects of Fructose and Temperature on the Micellization of a Cationic Gemini Surfactant,Pentanediyl-1,5-bis(dimethylcetylammonium) Bromide in Aqueous Solutions

By the conductivity measurements the effects of fructose and temperature (293–308 K) on the micellization of a cationic gemini surfactant (GS), pentanediyl-1,5-bis(dimethylcetylammonium) bromide in aqueous solutions have been investigated. The critical micelle concentration (CMC) of GS was measured at the different temperatures and fructose concentrations. An increasing trend of the CMC values is with addition of fructose. With increasing temperature, the CMC values are in a similar increasing trend. The CMC of GS by dye solubilization method at room temperature have been determined. The standard Gibbs energy, enthalpy and entropy of GS micellization have been evaluated. From these thermodynamic parameters, it was found that in presence of fructose, the stability of the GS aqueous solutions decreases.     

Effect of lysozyme adsorption on the interfacial rheology of DPPC and cholesteryl myristate films

A model tear film lipid layer composed of a binary mixture of cholesteryl myristate (CM) and 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC) was characterized using surface tension measurements, Brewster angle microscopy (BAM) and interfacial stress rheology (ISR). Isotherms showed that films containing >or=90 mol % CM have a 17-fold greater % area loss between the first and second compressions than the films with less CM. BAM images clearly showed that CM films did not expand after compression, and solid-like regions extending 1-2 mm were observed at low pressures (1 mN/m). Lipid films with or=50 mol % CM became elastic at higher surface pressures. Increasing CM content reduced the surface pressure at which the mixed film became elastic. Lysozyme adsorption into a CM film increased the compressibility and resulted in a more expanded film. Lysozyme increased the ductility of the CM/DPPC films with no film breakdown occurring up to the highest pressure measured (40 mN/m). In summary, CM increased the elasticity of the lipid films, but also caused them to become brittle and incapable of expansion following compression. Lysozyme adsorption increased the ductility and decreased the isotherm hysteresis for CM/DPPC films.     

Conformational memories with variable bond angles

Conformational Memories (CM) is a simulated annealing/Monte Carlo method that explores peptide and protein dihedral conformational space completely and efficiently, independent of the original conformation. Here we extend the CM method to include the variation of a randomly chosen bond angle, in addition to the standard variation of two or three randomly chosen dihedral angles, in each Monte Carlo trial of the CM exploratory and biased phases. We test the hypothesis that the inclusion of variable bond angles in CM leads to an improved sampling of conformational space. We compare the results with variable bond angles to CM with no bond angle variation for the following systems: (1) the pentapeptide Met-enkephalin, which is a standard test case for conformational search methods; (2) the proline ring pucker in a 17mer model peptide, (Ala)(8)Pro(Ala)(8); and (3) the conformations of the Ser 7.39 chi(1) in transmembrane helix 7 (TMH7) of the cannabinoid CB1 receptor, a 25-residue system. In each case, analysis of the CM results shows that the inclusion of variable bond angles results in sampling of regions of conformational space that are inaccessible to CM calculations with only variable dihedral angles, and/or a shift in conformational populations from those calculated when variable bond angles are not included. The incorporation of variable bond angles leads to an improved sampling of conformational space without loss of efficiency. Our examples show that this improved sampling leads to better exploration of biologically relevant conformations that have been experimentally validated.     

Inductively Coupled Plasma-Mass Spectrometry (ICP/MS) Based Methodology for Metal Speciation Analysis in Chinese Herbal Medicine

One of the major problems in marketing Chinese Medicinal (CM) material product is the issue of product safety. Alarm has been heightened internationally in recent years to control the contents of metals such as Cd, Pb, Hg and As and toxic contaminants such as residue pesticides in CM product. Cases of severe and fatal poisoning have occurred after the consultation of contaminated CM products, or adulterated ones containing toxic substitutions. Such incidences have severely damaged the overall image of CM products. It therefore comes as no surprise that in the recommendations put forward recently in China, the control of metals and toxic contaminants in CM products is a top priority item requiring proper action.     

Insight into Seasonal Change of Phytochemicals,Antioxidant, and Anti-Aging Activities of Root Bark of Paeonia suffruticosa (Cortex Moutan) Combined with Multivariate Statistical Analysis

Chemical compositions, antioxidants, and anti-aging activities of Cortex Moutan (CM), from different collection periods and different producing areas, were measured and compared in order to obtain excellent CM extracts. The bioactivities of CM extracts were examined by an in vitro antioxidant method and a UVB irradiated human dermal fibroblast (HDF) model. Phytochemical properties were obtained from ultra-fast liquid chromatography quadrupole time-of-flight mass spectrometry (UFLC-Q-TOF-MS) prior to the multivariate statistical analysis. As for the results, the extracts of Heze CM (HZCM) and Luoyang CM (LYCM) collected in June had better in vitro antioxidant activities, significantly increased the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and reduced the content of malondialdehyde (MDA), compared to other CM extracts. HZCM and LYCM extracts could upregulate the relative expression of SOD and GSH-Px mRNA. The extract of HZCM collected in June could significantly repress the production of matrix metalloproteinase 1 (MMP-1) and improve the production of procollagen type I (PCOL)-I in UVB irradiated HDF. In total, 50 compounds, including 17 monoterpenoids, 19 flavonoids, 13 phenols, and 1 amino acid were identified or tentatively identified in the CM extracts. Gallic acid, p-hydroxybenzoic acid, oxypaeoniflorin, paeoniflorin, 1,2,3,4,6-O-pentagalloyl glucose, and paeonol were predominant compounds in the CM extracts. Taken together, CM collected from April to September had better antioxidant and anti-aging effects for external usage.     

Study on the Synthesis of Metabolite of Clausenamide （CM1）

(-) Clausenamide (1) showed strong nootropic action, while its (+) antipode had no such an action. The content of CM1(2) in the metabolites of (-)1 is much higher than that of (+)11. For comparing the nootropic activity of enantiomers, (+) and (-) CM1 were synthesized. CM1 is the hydroxylated product of the N-methyl group of clausenamide. Oxidation of the C3-OH and C6-OH protected clausenamide to introduce the hydroxyl group into the methyl was tried but unsuccessful. Then de novo s…     

Olefin self-cross-metathesis catalyzed by the second-generation Grubbs carbene complex in room temperature ionic liquids

Olefin self-cross-metathesis (CM) reactions catalyzed by the second-generation Grubbs carbene complex have been compared in dichloromethane and two kinds of selected room temperature ionic liquids (RTILs). Both the catalyst and the ionic liquids could be simply recovered and reused for at least four cycles just with a little drop in activity. Significant enhancements in the reactivity, yield and reaction rate were achieved.     

Self-selection in olefin cross-metathesis: the effect of remote functionality

Olefin cross-metathesis (CM) is potentially an attractive method for generating dynamic combinatorial libraries (DCLs). In order for the CM reaction to be useful for DCL production, the course of the reaction and product distribution must be relatively insensitive to functionality remote from the reacting centers. We report on the CM of a series of allyl- and homoallylamides that are strongly dependent on remote functionality. This includes an unusual example of a cis-selective CM. [Reaction: see text]