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Background/Aims: Wool wax is a soft, yellow, waxy substance that is secreted by the sebaceous glands of sheep. The purpose of wool wax is to waterproof and protect the wool. Chemically, wool wax is a complex mixture of esters, fatty acids, and alcohols. Wool waxes with different prop­erties can be obtained by following different extraction methodologies. Methods: Two differently extracted wool waxes are compared in this study. Their effectiveness in mimicking the properties of skin lipids is evaluated. In addition, the lipid compositions and thermotropic behaviours of the 2 differently extracted wool waxes were evaluated. Results: The solvent-extracted wool wax was found to have a significantly higher polar lipid content than that of the water-extracted wool wax. This increase in the polar character of the solvent-extracted wool wax was also demonstrated by increased values of transition and degradation temperatures in the differential scanning calorimetry and thermogravimetric analyses, respectively. In addition, solvent-extracted wool wax demonstrated the ability to reinforce stratum corneum lipids, which led to improved skin barrier function. Conclusions: The suitability of the solvent-extracted wool wax for application in the preparation of cosmetics and dermatological products was demonstrated. [ABSTRACT FROM AUTHOR]

Change of the thermo-morphologic and thermotropic properties of liquid crystals exhibiting multiple phase transitions vs. thickness of liquid crystalline layer have been investigated in this work. The sandwich-cells with 20 μm, 70 μm, 120 μm, 170 μm and 240 μm thicknesses were used. Liquid crystalline materials with smectic C, smectic A and nematic mesophases were objects of investigations. Change of the crystal – smectic C , smectic C – smectic A , smectic A – nematic and nematic – isotropic liquid phase transition temperatures, and transformation of texture from specific types to non-specific types with change of thickness of liquid crystalline layer have been found. [ABSTRACT FROM AUTHOR]

New propylene bridged bis(imidazolium) salts bearing at the wingtip positions a benzyl group functionalised with one or two long alkyl chains, as well as the corresponding dinuclear N-heterocyclic dicarbene gold(I) complexes of general formula [Au 2 (RIm–(CH 2 ) 3 –ImR) 2 ](X) 2 (X = Br, PF 6 , BF 4 ) have been synthesised and thermally characterised. All the compounds are stable up to 200 °C and the bis(imidazolium) salts [H 2 (RIm–(CH 2 ) 3 –ImR)](X) 2 (X = Br, PF 6 ) behave as thermotropic liquid crystals in the temperature range 100–200 °C. By contrast, only the gold(I) diNHC complexes with eight aliphatic chains present mesomorphism, whereas those with four chains show numerous crystalline phases with structural disorder and presumably modified Au–Au distances, as indicated by solid state emission properties. [ABSTRACT FROM AUTHOR]

We report the thermotropic properties and measurements of the temperature and concentration dependences of the refractive index in isotropic micellar L phase and nematic-calamitic N mesophase of the hexadecyltrimethyl ammonium bromide/water (CTAB/HO) and hexadecyltrimethyl ammonium bromide/water/1-decanol (CTAB/HO/DeOH) lyotropic liquid crystalline systems. The effect of amphiphile and aliphatic alcohol concentrations on the refractive properties of L phase and N mesophase has been studied. Jump-like changes of the refractive properties in regions of the L phase- N mesophase lyotropic and thermotropic phase transitions have been found. The sufficient effect of CTAB addition on the refractive index value has been found for the CTAB/HO and CTAB/HO/DeOH lyotropic systems. In this work, the shape of micelles in L phase and N mesophase has been also estimated. Estimation showed that structural units of L phase are the isometric spherical micelles, and structural units of N mesophase are the anisometric rod-like micelles. Typical textures of N mesophase in the CTAB/HO and CTAB/HO/DeOH lyotropic systems and the heterophase regions of the N mesophase- isotropic liquid thermotropic phase transitions are presented. [ABSTRACT FROM AUTHOR]

The synthesis and investigations of the mesomorphic, thermotropic, thermo-morphologic, and thermo-optical properties of two new salicylaldimine compounds, synthesized by our group, are reported in this work. Temperature transformations of specific textures of the smectic C mesophase, taking place in these compounds, and thermo-morphologic and thermotropic properties of the biphasic regions for direct and reverse phase transitions have been investigated. Temperature hysteresis and enlargement of the biphasic regions have been found. The character of texture transformations and temperature behavior of the optical birefringence indicate to the first order a smectic C-isotropic liquid-phase transition in these salicylaldimine compounds. [ABSTRACT FROM AUTHOR]

Abstract: Arsenic (+3 oxidation state) methyltransferase (AS3MT) catalyzes the methylation of inorganic arsenic (iAs) and plays important role in the detoxication of this metalloid. There are fourteen cysteine residues in the human AS3MT (hAS3MT), among which twelve are absolutely conserved; Cys334 and Cys360 are unique; Cys368 and Cys369 are identified as a CysCys pair. The roles of several conserved cysteine residues in rat AS3MT and hAS3MT have been reported. Herein, the other conserved cysteine residues (Cys72, Cys271, Cys375) and the unique ones (Cys334, Cys360) were systematically replaced by serine using site-directed mutagenesis to study their functions. The mutants were investigated for enzymatic activity, kinetics, thermal stability and secondary structures. Present results indicate that C72S is completely inactive in methylation of iAs and has distinct changes in the secondary structures; Cys72 might form a critical intramolecular disulfide bond with Cys250; Cys271 and Cys375 do not affect the activity and structure of the hAS3MT. However, the mutations of Cys334 and Cys360 can decrease the enzymatic turnovers and change the conformation of the hAS3MT. The kinetic data show that Cys271, Cys334, Cys360 and Cys375 are not involved in the SAM binding. Additionally, all these cysteine residues except Cys375 affect the thermotropic properties of the hAS3MT. [ABSTRACT FROM AUTHOR]

In this work, the effect of thin films on the thermo-morphologic and thermotropic properties of the phase transitions between the nematic mesophase and isotropic liquid has been investigated. Investigations have been carried out for both the heating and cooling processes. The temperature and linear widths of the biphasic regions of the direct and reverse phase transitions in nematic liquid crystals versus thickness of the thin films have been calculated with a high accuracy. The shift of the nematic mesophase-isotropic liquid and the isotropic liquid-nematic mesophase phase transition temperatures to higher temperatures and the enlargement of the temperature and linear widths of the biphasic regions as the effect of surfaces have been found. [ABSTRACT FROM AUTHOR]

New thermotropic liquid crystals containing long octadecyloxy chain, one mesogen (Schiff base) and different functional end-groups such as biphenyl-4-carbonitrile, ethylcarbazole, 4-phenoxy, or 4-(heptadecafluoroctyl) were synthesized via an one-step route. Transition temperatures and phase characterization were studied by differential scanning calorimetry (DSC) and polarizing optical microscope (POM) techniques. The amine had an effect on the mesomorphic properties of the azomethines. As a result of DSC and POM investigations it was shown that liquid-crystalline properties of the azomethines exhibit a strong dependence of the end-groups. Based on the POM and DSC measurements the following mesophases were detected: smectic A, smectic B, and smectic G. In this article, we will present characterization of the liquid-crystalline azomethines of great interest for the emerging field of molecular electronics. [ABSTRACT FROM AUTHOR]

Abstract: Numerous PEI derived polymers have been explored for their use in gene delivery. Nine PEI-chol lipopolymers based on cholesterol grafting on three polyethyleneimines (PEI) of different molecular weights have been synthesized. Firstly their aggregation behavior has been studied using transmission electron microscopy and then their interactions with l-α-dipalmitoyl phosphatidylcholine (DPPC) membranes have been examined using fluorescence anisotropy and differential scanning calorimetry (DSC). These PEI-chol lipopolymers are found to quench the chain motion of the acyl chains of DPPC, when incorporated in membranes, depending upon the cholesterol grafting on PEI. These PEI-chol lipopolymers act as filler molecules in membranes. Electron microscopy shows the different aggregation behavior of these new PEI-chol lipopolymers depending upon the molecular weight of PEI and percentage of cholesterol grafting. Detailed analysis of the fluorescence anisotropy and DSC data indicate that the nature of perturbation induced by PEI-chol lipopolymers is dependent upon the molecular weight of the PEI used and the % of cholesterol grafting on PEI. In general, PEI-chol lipopolymers rigidify the liquid-crystalline phase of the membranes without any noticeable effect on the gel phase unlike natural cholesterol, which is known to fluidize the gel phase of the membranes. [Copyright &y& Elsevier]

Abstract: The role played by Ca2+ ions in the interaction of the human islet amyloid polypeptide (hIAPP) with model membranes has been investigated by differential scanning calorimetry (DSC) and circular dichroism (CD) experiments. In particular, the interaction of hIAPP and its rat isoform (rIAPP) with zwitterionic dipalmitoyl-phosphatidylcholine (DPPC), negatively charged dipalmitoyl-phosphatidylserine (DPPS) vesicles and with a 3:1 mixtures of them, has been studied in the presence of Ca2+ ions. The experiments have evidenced that amorphous, soluble hIAPP assemblies interact with the hydrophobic core of DPPC bilayers. Conversely, the presence of Ca2+ ions is necessary to activate a preferential interaction of hIAPP with the hydrophobic core of DPPS membranes. These findings support the hypothesis that an impaired cellular homeostasis of Ca2+ ions may promote the insertion of hIAPP into the hydrophobic core of carrier vesicles which is thought to contribute to an eventual intracellular accumulation of β-sheet rich hIAPP aggregates. [Copyright &y& Elsevier]

Abstract: We reported here the two-component self-assembling building blocks capable of forming lyotropic liquid crystal and liquid-crystalline physical gel. One of the components has a molecular characteristic of -symmetrical trisureas containing three azobenzene groups, which can form liquid-crystal phase in a temperature range of 133–215 °C. Another one has a trisamide core, which can self-aggregate to fibrous network through hydrogen bonds of amide moieties. The mixture of these two components performs lyotropic liquid crystal as well as liquid-crystalline physical gel in a temperature range larger than that of sole compound, suggesting that the cooperation of hydrogen bonds between these components stabilizes the mesophase of the assembly. The mechanism of formation of the mesophase was investigated by infrared spectra and small-angle X-ray scatterings. [Copyright &y& Elsevier]

Abstract: Peculiarities of the biphasic regions at the direct and reverse phase transitions between homeotropic oriented nematic mesophase and isotropic liquid have been investigated in detail in this work. The shift of phase transition temperatures to the low temperatures by the reverse phase transitions have been observed for this mesophase. Nonlinearity of thermotropic and thermo-optical properties at the phase transitions between nematic mesophase and isotropic liquid have been found. [Copyright &y& Elsevier]

Abstract: The mesomorphic, morphologic and thermotropic properties of the liquid crystalline material 4-hexyl-N-(4-hexadecyloxysalicylidene)aniline (1) have been investigated. Investigations on the peculiarities of heterophase regions during phase transitions between smectic C mesophase and isotropic liquid have been carried out. Hysteresis in the temperature width of the heterophase regions, temperatures of the phase transitions between smectic C and isotropic liquid, and smectic C and solid crystal and also the hysteresis in the temperature width of the smectic C mesophase in the salicylaldimine compound 1 have been found. [Copyright &y& Elsevier]