Search results for "X-Ray"

showing 10 items of 4234 documents

Two penta­de­hydro­peptides with different configurations of the ΔPhe residues

2009

Comparison of the crystal structures of two pentadehydropeptides containing DeltaPhe residues, namely (Z,Z)-N-(tert-butoxycarbonyl)glycyl-alpha,beta-phenylalanylglycyl-alpha,beta-phenylalanylglycine (or Boc(0)-Gly(1)-Delta(Z)Phe(2)-Gly(3)-Delta(Z)Phe(4)-Gly(5)-OH) methanol solvate, C(29)H(33)N(5)O(8) x CH(4)O, (I), and (E,E)-N-(tert-butoxycarbonyl)glycyl-alpha,beta-phenylalanylglycyl-alpha,beta-phenylalanylglycine (or Boc(0)-Gly(1)-Delta(E)Phe(2)-Gly(3)-Delta(E)Phe(4)-Gly(5)-OH), C(29)H(33)N(5)O(8), (II), indicates that the Delta(Z)Phe residue is a more effective inducer of folded structures than the Delta(E)Phe residue. The values of the torsion angles phi and psi show the presence of two …

chemistry.chemical_classificationMolecular StructureProtein ConformationOrganic CompoundsStereochemistryHydrogen bondPhenylalanineMolecular Sequence DataHydrogen BondingPhenylalanineGeneral MedicineCrystal structureCrystallography X-RayGeneral Biochemistry Genetics and Molecular BiologyAmino acidCrystallographyResidue (chemistry)Protein structurechemistryIntramolecular forceMoleculeAmino Acid SequenceOligopeptidesProtein BindingActa Crystallographica Section C-Crystal Structure Communications
researchProduct

Organization of Organic Molecules with Inorganic Molecular Species into Nanocomposite Biphase Arrays

1994

chemistry.chemical_classificationNanocompositeChemistryGeneral Chemical EngineeringCarboxylic acidInorganic chemistryGeneral ChemistryPhosphateMicellechemistry.chemical_compoundSulfonateLiquid crystalX-ray crystallographyMaterials ChemistryInorganic compoundChemistry of Materials
researchProduct

Investigation of α-amino acid N-carboxyanhydrides by X-ray diffraction for controlled ring-opening polymerization

2019

Abstract The need for a scalable synthesis of not sequence defined polypeptides as biomaterials is met by the ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs). Even though this polymerization technique appears straight forward, it holds pitfalls in terms of reproducibility and overall control over the polymerization conditions, which depends, beside choice of solvent or initiator, significantly on reagent purity. In addition, the synthesis of monomers can lead to the formation of racemic amino acids. Thus, in this work, we describe the benefits of highly pure monomers in order to control nucleophilic ring-opening polymerization NCAs. Hereby, monomer purity is investiga…

chemistry.chemical_classificationOrganic ChemistrySequence (biology)BiochemistryRing-opening polymerizationAmino acidchemistry.chemical_compoundMonomerchemistryNucleophilePolymerizationReagentDrug DiscoveryX-ray crystallographyPolymer chemistryTetrahedron Letters
researchProduct

Group 4 and Group 8 unbridged metallocene derivatives with a pendant fluorenyl group. X-ray structure of 1,1′-bis[2-(2-fluorenyl)propyl]ferrocene

1999

Abstract The action of one equivalent of BuLi on 2-cyclopentadienyl-2-fluorenylpropane (C5H5CMe2C13H9) led to the monoanionic salt LiC5H4CMe2C13H9. This anion was reacted with Fe2Cl4(THF)3, TiCl3(THF)3, ZrCl4, HfCl4 or CpZrCl3, DME and, in a mixture with CpLi, with Fe2Cl4(THF)3 affording the corresponding metallocenes and metallocene dichlorides. The X-ray structure of Fe(η5-C5H4CMe2C13H9)2 is described. The first results about the reactivity of the fluorenyl group are reported together with the synthesis of Zr(η5-C5H5)[η5-C5H4CMe2-η5-C13H8Rh(cod)]Cl2, which has been tested using hydroformylation and cyclotrimerisation catalysis.

chemistry.chemical_classificationOrganic ChemistryX-raySalt (chemistry)BiochemistryMedicinal chemistryCatalysisInorganic Chemistrychemistry.chemical_compoundFerrocenechemistryGroup (periodic table)Materials ChemistryOrganic chemistryReactivity (chemistry)Physical and Theoretical ChemistryMetalloceneHydroformylationJournal of Organometallic Chemistry
researchProduct

On the phase transition in CsCN

1983

X-ray diffraction and dielectric measurements have been performed on the molecular crystal CsCN as a function of temperature. The order parameter of the cubic to rhombohedral phase transition (Tc=186 K) was determined and interpreted by a coupling of the (CN)− orientations to the shear strain. At lower temperatures the dielectric response is dominated by thermally activated relaxations processes rather than by electrical ordering of the CN dipoles.

chemistry.chemical_classificationPermittivityDiffractionPhase transitionMaterials scienceCondensed matter physicsbusiness.industryPhysics::OpticsDielectricCondensed Matter PhysicsElectronic Optical and Magnetic MaterialsCondensed Matter::Materials ScienceDipoleOpticschemistryX-ray crystallographyGeneral Materials ScienceDielectric lossbusinessInorganic compoundZeitschrift f�r Physik B Condensed Matter
researchProduct

Phase transitions and distortion of [BiCl6]3- octahedra in (C3H5NH3)3[BiCl 6] - DSC and single-crystal X-ray diffraction studies

2004

The DSC diagram of tris(allylammonium) hexachlorobismuthate(III), (C3H5NH3)3[BiCl6], revealed three anomalies at 152, 191 and 299 K. The structure of the salt was determined at 200 and 315 K, below and above the high-temperature phase transition at 299 K. In both phases the crystals are monoclinic. At 200 K the space group is C2/c whereas at 315 K it is C2/m. The structures, at both temperatures, are composed of [BiCl6]3− octahedra and allylammonium cations. The organic and inorganic moieties are attracted to each other by a network of the N-H. . .Cl hydrogen bonds. The relationship between corresponding parameters of the unit cells has been found. The phase transition at 299 K, of the orde…

chemistry.chemical_classificationPhase transitionCrystallographyOctahedronChemistryHydrogen bondPhase (matter)X-ray crystallographySalt (chemistry)General ChemistrySingle crystalMonoclinic crystal system
researchProduct

Phases and phase transitions of (NaCl)1?x(NaCN)x

1985

(NaCl)1−x(NaCN)x mixed crystals with CN-concentrationsx of 0.87, 0.76, 0.71 and 0.65 have been investigated by X-ray powder diffraction. Apart from the cubic room temperature phase, a rhombohedral and an orthorhombic phase have been identified. In addition a glass state has been observed which is characterized by a strong broadening of the cubic powder lines. The phase diagram shows a wide coexistence gap between the non-cubic phases and the glass state.

chemistry.chemical_classificationPhase transitionMaterials scienceAnalytical chemistryCondensed Matter PhysicsElectronic Optical and Magnetic MaterialsPolymorphism (materials science)chemistryX-ray crystallographyGeneral Materials ScienceOrthorhombic crystal systemInorganic compoundPowder diffractionPhase diagramSolid solutionZeitschrift f�r Physik B Condensed Matter
researchProduct

Phase behavior and elastic properties of a slightly crosslinked liquid crystalline main-chain polymer

1990

A liquid crystalline main-chain polymer was slightly crosslinked by a reaction withα, ω-difunctionalized oligo-siloxanes. Crosslinking does not disturb the liquid crystalline phases, which are identified by x-ray measurements as smecticB and smecticA phases. Measurements of the elastic properties of the crosslinked sample show rubber-like elasticity, even in the liquid crystalline phases. A difference of 7 K was found between cooling and heating for the smecticA/isotropic transition from DSC and mechanical measurements.

chemistry.chemical_classificationPhase transitionMaterials sciencePolymers and PlasticsIsotropyPolymerShear modulusColloid and Surface ChemistryDifferential scanning calorimetrychemistryChemical engineeringLiquid crystalX-ray crystallographyMaterials ChemistryOrganic chemistryPhysical and Theoretical ChemistryElasticity (economics)Colloid & Polymer Science
researchProduct

Selective photocatalytic oxidation of 3-pyridinemethanol on platinized acid/base modified TiO2

2021

TiO2 catalysts, modified with acidic or alkaline solutions and then platinized, were used for the partial photocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B-3 under environmentally friendly conditions. The reaction took place in water under UVA light and air oxygen. Catalysts were characterized by TEM, photoluminescence, DRIFT-IR, Raman, DRS, XPS, and photocurrent measurements. The photocatalytic activity results show that Pt loading of untreated samples leads to a significant activity improvement (hence product yield) as much as acid and alkaline treatments do. Moreover, the alkaline treated TiO2 samples exhibit a further increase in activity after loading w…

chemistry.chemical_classificationPhotocurrentElectron transferchemistryX-ray photoelectron spectroscopyBase (chemistry)Photocatalysischemistry.chemical_elementThermal stabilityOxygenCatalysisNuclear chemistryCatalysis
researchProduct

Electronic Perspective on the Electrochemistry of Prussian Blue Films

2009

The derivative of the voltabsommetric scans, together with previous nano-electrogravimetric and X-ray diffraction results, allow different electrochemical processes to be distinguished during the Prussian blue (PB) voltammetric scan. Potassium, proton, and hydrated proton counterions involved in PB electrochemistry are related here to the electrochemical reactions of specific Fe sites. Potassium counterions show two different sites for their insertion: one located in the crystalline framework and another in ferrocyanide vacancies. From the monitoring of electroactive Fe sites, the covalent-exchange model is suggested as one of the first approaches to explain the origin of the PB magnetic or…

chemistry.chemical_classificationPrussian blueProtonIon exchangeRenewable Energy Sustainability and the EnvironmentPotassiumInorganic chemistrychemistry.chemical_elementCondensed Matter PhysicsElectrochemistrySurfaces Coatings and FilmsElectronic Optical and Magnetic Materialschemistry.chemical_compoundchemistryX-ray crystallographyMaterials ChemistryElectrochemistryCounterionFerrocyanideJournal of The Electrochemical Society
researchProduct