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Molecules Leads (molecule + lead)
Selected AbstractsDiscrimination between diastereoisomeric dipeptides by IR,UV double resonance spectroscopy and ab initio calculationsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2005Ali G. Abo-Riziq Abstract We studied diastereoisomeric dipeptides, containing two chiral centers, by comparing ab initio calculations with laser desorption jet-cooling experiments. We studied the hetero-dipeptides LL,VF (L-Val-L-Phe) and DL,VF and the homo-dipeptides LL,FF (L-Phe-L-Phe) and LD,FF. Changing one of the chiral centers in each molecule leads to changes in the spectra that can be used to distinguish between diastereoisomeric pairs. We observed three different conformers for LL,VF, four for DL,VF, two for LL,FF, and one for LD,FF. By comparing the results from IR,UV double resonant spectroscopy with ab initio calculations, we can draw conclusions about the conformational structures. At the same time, the experimental data serve as a test for the computational results. We discuss the possibilities and limitations of the interplay between theory and experiment. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Refinement of modulated structures against X-ray powder diffraction data with JANA2000JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2001M. Du JANA is a computer program for the refinement and analysis of periodic and aperiodic (incommensurately modulated structures and composite crystals) crystal structures. Here a new module is introduced that allows Rietveld refinements against powder diffraction data. It is shown that JANA2000 provides a state-of-the-art description of the peak profiles. A re-analysis of the low-temperature structure of (CO)xC60 showed that the application of icosahedral symmetry restrictions to the C60 molecule leads to a better description of the electron density and to a corrected position of the CO molecule as compared with a rigid-body refinement. The incommensurately modulated structure of NbTe4 has been successfully refined against X-ray powder diffraction data. The structural parameters are equal to, but less accurate, than the parameters obtained from a single-crystal study. [source] Deletion of either CD55 or CD97 ameliorates arthritis in mouse modelsARTHRITIS & RHEUMATISM, Issue 4 2010Robert M. Hoek Objective CD55 (decay-accelerating factor) is best known for its role in the negative regulation of the complement system. Indeed, lack of this molecule leads to disease aggravation in many autoimmune disease models. However, CD55 is abundantly present on fibroblast-like synoviocytes and is also a ligand of the adhesion-class heptahelical receptor CD97, which is expressed by infiltrating macrophages. Treatment with antibodies to CD97 ameliorates the collagen-induced model of rheumatoid arthritis (RA) in DBA/1 mice, but the net contribution of CD55 is unknown. This study was undertaken to investigate the role of CD55 in experimental RA. Methods Arthritis was induced in wild-type, CD55,/,, and CD97,/, mice using collagen-induced and K/BxN serum,transfer models. Incidence of arthritis was monitored over time, and disease activity was assessed by clinical and immunohistochemical evaluation. Results In contrast to observations in many inflammatory disease models, lack of CD55 resulted in decreased arthritis in experimental models of RA. Consistent with the previously reported effects of anti-CD97 antibody treatment, CD97,/, mice had reduced arthritis activity compared with wild-type controls. Conclusion Our findings indicate that the lack of CD55 or CD97 in 2 different models of arthritis increases resistance to the disease. These findings provide insight into a role for CD55 interaction with CD97 in the pathogenesis of RA and suggest that therapeutic strategies that disrupt CD55/CD97 may be clinically beneficial. [source] Photophysical Processes in ,Supramolecular Balls' Formed by Lanthanide Chloride with 2,2,-BipyridineHELVETICA CHIMICA ACTA, Issue 11 2009Abstract The europium complex [EuCl2(bpy)2(H2O)2]Cl,1.25,C2H6O,0.37,H2O, where bpy is 2,2,-bipyridine, was synthesized and investigated with the aim to relate its molecular geometry and crystal packing to the efficiency of energy-transfer processes. The presence of H-bonds between noncoordinated Cl, ions and coordinated H2O molecules leads to the formation of discrete trimers assembled by a number of CH,,,Cl and stacking interactions into ,supramolecular balls' which contain Cl, ions and solvate molecules (H2O and EtOH). The additional stabilization of the complex is due to intramolecular N,,,C interactions between two bpy ligands that causes some shortening of the EuN bonds. Deciphering the luminescence properties of the Eu complex was performed under consideration of both the composition of the inner coordination sphere and the peculiarities of the crystal packing. The influence of the latter and the bpy orientation on the energy of the ligand,Eu charge-transfer state (LMCT) was established, and an additional excited state induced by the , -stacking interaction (SICT) was identified. [source] Electronic Decoupling of Aromatic Molecules from a Metal by an Atomically Thin Organic Spacer,ADVANCED MATERIALS, Issue 23 2008Roman Forker Electronic coupling effects of organic adsorbates to metallic surfaces are examined optically. Covering a Au(111) substrate with an ultrathin (,0.3 nm) nanographene-like layer of flat lying molecules leads to decoupling of further molecular layers to a large extent. Our work suggests that not only inorganic salts or oxides can be used as insulating spacers but also particular organic monolayers. [source] Dynamics of end grafted DNA molecules and possible biosensor applicationsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2006C. Sendner Abstract Polymers that are terminally attached to solid supports, so called brushes, form the basis for a wide variety of different applications in colloidal and biophysical sciences. For grafted charged chains a conducting surface allows to manipulate the brush structure by applying electric fields across the brush. The dynamics of oligomeric DNA molecules under the action of repulsive and attractive surface electric fields is studied by Brownian dynamics simulations including hydrodynamic effects and compared to experimental results. The difference in flexibility between double and single stranded DNA molecules leads to a change in the switching dynamics when repeatedly reversing the surface charge. This effect allows to detect hybridization of surface anchored DNA. Similar kinetic changes occur when other molecules bind terminally to DNA, opening the possibility to use end grafted polymers for general biosensing applications. We in particular discuss the influence of the adsorbate size and change on the switching dynamics. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of solvent on the structures of two one-dimensional cobalt(II) coordination polymers with tetrachloroterephthalateACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009Yong-Qin Fang The title cobalt coordination polymers, catena -poly[[[aquatripyridinecobalt(II)]-,-tetrachloroterephthalato] pyridine solvate], {[Co(C8Cl4O4)(C5H5N)3(H2O)]·C5H5N}n, (I), and catena -poly[[[diaquadipyridinecobalt(II)]-,-tetrachloroterephthalato] 1,4-dioxane trihydrate], {[Co(C8Cl4O4)(C5H5N)2(H2O)2]·C4H8O2·3H2O}n, (II), have been prepared with tetrachloroterephthalic acid (H2BDC-Cl4) under different solvent media. Both complexes form infinite cobalt(II),tetrachloroterephthalate polymeric chains. In (I), two independent CoII ions are six-coordinated through N3O3 donor sets in slightly distorted octahedral geometries provided by two carboxylate and three pyridine ligands, and one water molecule. The structure of (II) contains two independent CoII atoms, each lying on a twofold axis, which adopt a tetragonally distorted N2O4 octahedral geometry via two carboxylate groups, two pyridine ligands and two water molecules. The different stoichiometry of coordinated and solvent guest molecules leads to different two-dimensional supramolecular networks, with (I) utilizing C,H..., and weak ,,, interactions and (II) utilizing mainly conventional hydrogen bonding. [source] | ||||||||||