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Coupling Reagents (coupling + reagent)
Kinds of Coupling Reagents Selected AbstractsEthyl Propiolate: A Simple and Convenient Peptide Coupling Reagent.CHEMINFORM, Issue 1 2005Bogdan Iorga Abstract For Abstract see ChemInform Abstract in Full Text. [source] Thermal conductivity and mechanical properties of aluminum nitride filled linear low-density polyethylene compositesPOLYMER ENGINEERING & SCIENCE, Issue 5 2009Junwei Gu To acquire polymer composites with high thermal conductivity and mechanical properties, the aluminum nitride (AlN) microparticles modified with titanate coupling reagent of isopropyltrioleictitanate (NDZ-105) were employed to blend linear low-density polyethylene (LLDPE) via powder mixing method. Thermal conductive coefficient of the AlN/LLDPE composites was measured using hot disk thermal analyzer, and the thermal stability characteristics of AlN/LLDPE composites were mainly investigated via thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC). The results indicated that the use of AlN particles modified by NDZ-105 significantly enhanced thermal conductivity and mechanical properties of AlN/LLDPE composites. The thermal conductivity coefficient , was 1.0842 W/mk with 30% volume fraction of AlN, about three times higher than that of native LLDPE. The tensile strength of composites was maximum (17.42 MPa) with 20% mass fraction of AlN. DSC analyses results indicated that AlN had an influence on the melting temperature and the crystallinity of LLDPE. Additionally, TGA analyses showed that the thermal stability of LLDPE was significantly increased with addition of AlN. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Blind crystal structure prediction of a novel second polymorph of 1-hydroxy-7-azabenzotriazoleACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2006Harriott Nowell The commercially available peptide coupling reagent 1-hydroxy-7-azabenzotriazole has been shown to crystallize in two polymorphic forms. The two polymorphs differ in their hydrogen-bonding motif, with form I having an (10) dimer motif and form II having a C(5) chain motif. The previously unreported form II was used as an informal blind test of computational crystal structure prediction for flexible molecules. The crystal structure of form II has been successfully predicted blind from lattice-energy minimization calculations following a series of searches using a large number of rigid conformers. The structure for form II was the third lowest in energy with form I found as the global minimum, with the energy calculated as the sum of the ab initio intramolecular energy penalty for conformational distortion and the intermolecular lattice energy which is calculated from a distributed multipole representation of the charge density. The predicted structure was sufficiently close to the experimental structure that it could be used as a starting model for crystal structure refinement. A subsequent limited polymorph screen failed to yield a third polymorphic form, but demonstrated that alcohol solvents are implicated in the formation of the form I dimer structure. [source] PNA synthesis using a novel Boc/acyl protecting group strategyJOURNAL OF PEPTIDE SCIENCE, Issue 8 2001Thomas Kofoed Abstract The synthesis of novel Boc/acyl protected monomers for the synthesis of peptide nucleic acid (PNA) is described. The oligomerization protocol using these new monomers has been optimized with regard to coupling reagents. The use of base-labile acyl protecting groups at the exocyclic amines of the heterocyclic bases (isobutyryl for guanine and benzoyl for adenine and cytosine) and a PAM-linked solid support offers an attractive alternative to the present procedures used in PNA synthesis. This strategy has been applied for the synthesis of a test 17mer PNA on both control pore glass (CPG) and a polystyrene MBHA support and was used in the preparation of PNA,DNA chimeras. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd. [source] Solid-phase synthesis and characterization of N -methyl-rich peptidesCHEMICAL BIOLOGY & DRUG DESIGN, Issue 2 2005M. Teixidó Abstract:, A library of peptides required for a project investigating the factors relevant for blood,brain barrier transport was synthesized on solid phase. As a result of the high N -methylamino acid content in the peptides, their syntheses were challenging and form the basis of the work presented here. The coupling of protected N -methylamino acids with N -methylamino acids generally occurs in low yield. (7-azabenzotriazol-1-yloxy)-tris(pyrrolidino)phosphonium hexafluorophosphate (PyAOP) or PyBOP/1-hydroxy-7-azabenzotriazole (HOAt), are the most promising coupling reagents for these couplings. When a peptide contains an acetylated N -methylamino acid at the N-terminal position, loss of Ac- N -methylamino acid occurs during trifluoroacetic acid (TFA) cleavage of the peptide from the resin. Other side reactions resulting from acidic cleavage are described here, including fragmentation between consecutive N -methylamino acids and formation of diketopiperazines (DKPs). The time of cleavage is shown to greatly influence synthetic results. Finally, high-performance liquid chromatography (HPLC) profiles of N -methyl-rich peptides show multiple peaks because of slow conversion between conformers. [source] Highly efficient synthesis of peptides by rational utilization of novel coupling reagentsCHINESE JOURNAL OF CHEMISTRY, Issue 4 2000Li Peng Abstract The efficiency of different peptide coupling reagents, including carbodiimides, HOBt or HOAt-derived uronium, phosphonium and immonium salts, halouronium, halophosphonium, 2-halopyridinium and 2-halothiazolium salts, was evaluated. The synthetic strategy for coded peptides and nonribosomal peptides was discussed with an emphasis on the rational selection of peptide coupling reagents. [source] | ||||||||||