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Single Monomer (single + monomer)
Selected AbstractsVersatile preparation of poly(1,4-phenylenevinylene- co -1,4-phenylene-1,2-ethanediyl) by CVD polymerization of p -(methoxymethyl)benzyl chlorideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2005Ngo Trinh Tung Abstract It was demonstrated that a series of copolymers consisting of 1,4-phenylenevinylene (PV) and 1,4-phenylene-1,2-ethanediyl (PE) units could be prepared from a single monomer, p -(methoxymethyl)benzyl chloride, via the chemical vapor deposition polymerization (CVDP) method. The composition of the copolymers could be varied simply by altering the monomer activation temperature. The higher the temperature, the lower the content of the PV unit. The photo (PL)- and electroluminescence (EL) properties of the copolymers that revealed a blueshift when compared with PPV strongly depend on the amount of the PE units incorporated. The external quantum efficiencies of the electroluminescence devices having the configuration of ITO/PEDOT-PSS/copolymer/Al-Li were higher than that of PPV, which can be ascribed to the improved confinement of excitons. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 742,751, 2005 [source] Type II dehydroquinase: molecular replacement with many copiesACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2008Kirsty Anne Stewart Type II dehydroquinase is a small (150-amino-acid) protein which in solution packs together to form a dodecamer with 23 cubic symmetry. In crystals of this protein the symmetry of the biological unit can be coincident with the crystallographic symmetry, giving rise to cubic crystal forms with a single monomer in the asymmetric unit. In crystals where this is not the case, multiple copies of the monomer are present, giving rise to significant and often confusing noncrystallographic symmetry in low-symmetry crystal systems. These different crystal forms pose a variety of challenges for solution by molecular replacement. Three examples of structure solutions, including a highly unusual triclinic crystal form with 16 dodecamers (192 monomers) in the unit cell, are described. Four commonly used molecular-replacement packages are assessed against two of these examples, one of high symmetry and the other of low symmetry; this study highlights how program performance can vary significantly depending on the given problem. In addition, the final refined structure of the 16-dodecamer triclinic crystal form is analysed and shown not to be a superlattice structure, but rather an F -centred cubic crystal with frustrated crystallographic symmetry. [source] Purification, crystallization and preliminary X-ray analysis of Caenorhabditis elegans ubiquitin-conjugation enzyme M7.1ACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2003José A. Gavira M7.1 is a class IV ubiquitin-conjugation enzyme (UBC) that belongs to the ubiquitination cascade in Caenorhabditis elegans. The clone for this UBC has been overexpressed in Escherichia coli and the 16.7,kDa protein was purified from the soluble fraction. M7.1 was crystallized by sitting-drop vapor diffusion in 10% ethanol, 1.5,M NaCl at 277.5,K. Crystals diffracted to 1.75,Å and belong to the orthorhombic space group P212121, with unit-cell parameters a = 44.3, b = 54.3, c = 60.2,Å. The asymmetric unit contains a single monomer. A molecular-replacement model has been determined and refinement is in progress. [source] Cloning, expression, crystallization and preliminary X-ray crystallographic analysis of ,-ketoacyl-ACP synthase III (FabH) from Xanthomonas oryzae pv. oryzaeACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2009Kim-Hung Huynh The bacterial ,-ketoacyl-ACP synthase III (KASIII) encoded by the gene fabH (Xoo4209) from Xanthomonas oryzae pv. oryzae, a plant pathogen, is an important enzyme in the elongation steps of fatty-acid biosynthesis. It is expected to be one of the enzymes responsible for bacterial blight (BB), a serious disease that results in huge production losses of rice. As it represents an important target for the development of new antibacterial drugs against BB, determination of the crystal structure of the KAS III enzyme is essential in order to understand its reaction mechanism. In order to analyze the structure and function of KAS III, the fabH (Xoo4209) gene was cloned and the enzyme was expressed and purified. The KASIII crystal diffracted to 2.05,Å resolution and belonged to the orthorhombic space group P21212, with unit-cell parameters a = 69.8, b = 79.5, c = 62.3,Å. The unit-cell volume of the crystal is compatible with the presence of a single monomer in the asymmetric unit, with a corresponding Matthews coefficient VM of 2.27,Å3,Da,1 and a solvent content of 45.8%. [source] Stabilization of collagen by the plant polyphenolics Acacia mollissima and Terminalia chebulaJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008G. Krishnamoorthy Abstract The central role of collagen as the major structural fibrous protein in the mammalian extracellular matrix has motivated a significant effort toward the determination of its mechanical properties at all levels, ranging from single monomers and long-chain polymers to a structural element within a biological tissue. However, the stabilization of collagen against collagenolytic degradation finds significance in biomedical and industrial applications. Tannins are plant-derived polyphenols that have the ability to inhibit the collagenase activity at minimum concentration. The inhibitory effect of wattle (Acacia mollissima) and myrobalan (Terminalia chebula) on the action of collagenase against collagen was probed in this study. The kinetics of the inhibition of collagenase by wattle and myrobalan was deduced from the extent of hydrolysis of 2-furanacryloyl,L -leucyl,glycyl,L -prolyl,L -alanine. Both wattle and myrobalan tannin exhibited competitive modes of inhibition against collagenase. Circular dichroism studies of collagenase on treatment with wattle and myrobalan revealed changes in the secondary structure of collagenase. These results suggest that the tannins of A. mollissima and T. chebula extracts facilitated collagen stabilization through collagenase inhibition. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] | |||||||||||||