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Crystal Properties (crystal + property)
Selected AbstractsSmectic phases of liquid crystals based on dinuclear palladium(II) complexes with carboxylato bridgeCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2010V. Cîrcu Abstract In this paper we present the preparation and the investigation of the liquid crystal properties of a series of dinuclear carboxylato bridge Pd(II) complexes bearing six alkoxy peripheral chains in the molecule. Their structures were assigned based on elemental analysis, IR and 1H NMR spectroscopy whereas the thermal behaviour was investigated by polarizing optical microscopy and differential scanning calorimetry. The monotropic smectic A phase displayed by these materials was identified by miscibility studies with a previously reported mesogen. It was found that the transition temperatures and the SmA mesophase stability depend on the alkyl chain length of the carboxylato bridge. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis, pharmacology, crystal properties, and quantitative solvation studies from a drug transport perspective for three new 1,2,4-thiadiazolesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2010German L. Perlovich Abstract A novel 1,2,4-thiadiazoles were synthesized. Crystal structures of these compounds were solved by X-ray diffraction experiments and comparative analysis of molecular conformational states, packing architecture, and hydrogen bonds networks were carried out. Thermodynamic aspects of sublimation processes of studied compounds were determined using temperature dependencies of vapor pressure. Thermophysical characteristics of the molecular crystals were obtained and compared with the sublimation and structural parameters. Solubility and solvation processes of 1,2,4-thiadiazoles in buffer, n -hexane and n -octanol were studied within the wide range of temperature intervals and thermodynamic functions were calculated. Specific and nonspecific interactions of molecules resolved in crystals and solvents were estimated and compared. Distribution processes of compounds in buffer/n -octanol and buffer/n -hexane systems (describing different types of membranes) were investigated. Analysis of transfer processes of studied molecules from the buffer to n -octanol/n -hexane phases was carried out by the diagram method with evaluation of the enthalpic and entropic terms. This approach allows us to design drug molecules with optimal passive transport properties. Calcium-blocking properties of the substances were evaluated. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3754,3768, 2010 [source] Thermodynamic and structural aspects of sulfonamide crystals and solutionsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2009German L. Perlovich Abstract The crystal structures of three sulfonamides with the general structure 4-NH2 -C6H4 -SO2NH-C6H4/3 -R (R,=,4-Et; 4-OMe; 5-Cl-2-Me) have been determined by X-ray diffraction. On the basis of our previous data and the results obtained a comparative analysis of crystal properties was performed: molecular conformational states, packing architecture, and hydrogen bond networks using graph set notations. The thermodynamic aspects of the sulfonamide sublimation process have been studied by investigating the temperature dependence of vapor pressure using the transpiration method. A regression equation was derived describing the correlation between sublimation entropy terms and crystal density data calculated from X-ray diffraction results. Also correlations between sublimation Gibbs energies and melting points, on the one hand, and between sublimation enthalpies and fusion enthalpies at 298 K, on the other hand, were found. These dependencies give the opportunity to predict sublimation thermodynamic parameters by simple thermo-physical experiments (fusion characteristics). Solubility processes of the compounds in water, n -hexane, and n -octanol (as phases modeling various drug delivery pathways and different types of membranes) were investigated and corresponding thermodynamic functions were calculated as well. Thermodynamic characteristics of sulfonamide solvation were evaluated. For compounds with similar structures processes of transfer from one solvent to another one were studied by a diagram method combined with analysis of enthalpic and entropic terms. Distinguishing between enthalpy and entropy, as is possible through the present approach, leads to the insight that the contribution of these terms is different for different molecules (entropy- or enthalpy-determined). Thus, in contrast to interpretation of only the Gibbs energy of transfer, being extensively used for pharmaceuticals in the form of the partition coefficient (log,P), the analysis of thermodynamic functions of the transfer process provides additional mechanistic information. This may be important for further evaluation of the physiological distribution of drug molecules and may provide a better understanding of biopharmaceutical properties of drugs. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4738,4755, 2009 [source] Structural and optical characterization of (11-22) semipolar GaN on m -plane sapphire without low temperature buffer layerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Sung-Nam Lee Abstract We reported the high quality semipolar (11-22) GaN grown on m-sapphire by using the novel two-step growth method without low temperature GaN or AlN buffer layer. It is found that macroscopic surface morphology of semipolar GaN epilayer was very smooth, while microscopic surface structure was arrowhead-like surface structure toward the direction of [1-21-1]. Anisotropic crystal properties of semipolar GaN/m-sapphire were also observed by two incident directions of X-ray beam. Therefore, we suggested that the anisotropic crystal properties and arrow-head like surface structure would be caused by heteroepitaxial crystallograhpic difference between semipolar GaN and m-sapphire. Additionally, photoluminescence (PL) measurements showed the strong bandedge emission of n-type semipolar GaN without yellow luminescence (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Single-crystal neutron diffraction investigation on crystals belonging to the langasite family: a comparative studyACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2010R. Chitra Crystals of the langasite family are of interest as they are piezoelectric in different devices. The properties of these classes of crystals can be modified within certain limits by isomorphous substitution. Single-crystal neutron diffraction studies were carried out for LGT (La3Ga5.5Ta0.5O14), LGST (La3Ga5.25Ta0.25Si0.5O14) and LGZrT (La3Ga5.25Ta0.25Zr0.5O14) as the neutron study gives a better average picture of the crystal properties over a macroscopic region of the grown crystal. The effect of small substitutions at various sites on the piezoelectric properties of the crystal was studied. [source] Application of protein engineering to enhance crystallizability and improve crystal propertiesACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2010Zygmunt S. Derewenda Until recently, protein crystallization has mostly been regarded as a stochastic event over which the investigator has little or no control. With the dramatic technological advances in synchrotron-radiation sources and detectors and the equally impressive progress in crystallographic software, including automated model building and validation, crystallization has increasingly become the rate-limiting step in X-ray diffraction studies of macromolecules. However, with the advent of recombinant methods it has also become possible to engineer target proteins and their complexes for higher propensity to form crystals with desirable X-ray diffraction qualities. As most proteins that are under investigation today are obtained by heterologous overexpression, these techniques hold the promise of becoming routine tools with the potential to transform classical crystallization screening into a more rational high-success-rate approach. This article presents an overview of protein-engineering methods designed to enhance crystallizability and discusses a number of examples of their successful application. [source] Crystallization of Clonorchis sinensis 26,kDa glutathione S-transferase and its fusion proteins with peptides of different lengthsACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2001Young-Hyun Han A Clonorchis sinensis 26,kDa glutathione S-transferase (CsGST) and its fusion proteins containing 14 and 48 amino-acid peptides at the N-terminus have been crystallized using polyethylene glycol monomethylether 550 as a precipitant. Crystals of the three proteins show very similar crystal properties: they diffract to at least 2.3,Å resolution and belong to the orthorhombic space group P212121. The unit-cell parameters of CsGST crystals were a = 66.64,(1), b = 68.91,(1), c = 123.41,(2),Å, which are very close to those of the crystals of the two fusion proteins. In addition, CsGST fusion proteins containing varying extents of N-terminal-extended peptides are incorporated into a crystal, indicating that the extended peptides have little effect on crystal packing. These results suggest that the crystallization system of CsGST/peptide fusion protein may be generally applicable to obtain crystals of small peptides. [source] Synthesis and characterization of 4,4,-dihydroxy-,-methylstilbene crystalCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2006K. Rameshbabu Abstract 4,4,-dihydroxy-,-methylstilbene (DHAMS) was synthesized by condensation reaction with chloroacetone and phenol in the presence of concentrated sulfuric acid, and has been successfully grown by solution growth technique. This is the first report in the literature on the crystallization of DHAMS and exhibited the birefringent melt (liquid crystal property) of the optical properties. FTIR and FTNMR studies are in accordance with the structure. Good quality crystals were grown by slow evaporation technique by acetone as solvent. A transmission spectrum of the crystal was obtained in the region of 285 nm. The structural and optical properties were studied. (© 2006 WILEY-VCH Verlag GmbH & Co. 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