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Dimer Equilibrium (dimer + equilibrium)
Selected AbstractsNMR,spectroscopic investigation of o-nitrosobenzoic acidMAGNETIC RESONANCE IN CHEMISTRY, Issue 12 2008Klaus Schaper Abstract The synthesis of o -nitrosobenzoic acid 2 has been known for more than 100 years, and the photochemical preparation from o -nitrobenzaldehyde 1 became a textbook example for [1,5]-hydrogen shifts. However, neither the 1H,NMR spectra nor the 13C{1H},NMR of this compound have been reported so far. This fact can most likely be attributed to the monomer,dimer equilibrium of the nitrosobenzoic acid, which leads to rather complex, concentration-dependent NMR spectra. In this paper, we report a thorough investigation of these spectra. In the 13C-{1H}-NMR spectra, all 21 lines could be assigned to the monomeric form, the E -dimer, and the Z -dimer. Copyright © 2008 John Wiley & Sons, Ltd. [source] Backbone dynamics of SDF-1, determined by NMR: Interpretation in the presence of monomer,dimer equilibriumPROTEIN SCIENCE, Issue 11 2006Olga K. Baryshnikova Abstract SDF-1, is a member of the chemokine family implicated in various reactions in the immune system. The interaction of SDF-1, with its receptor, CXCR4, is responsible for metastasis of a variety of cancers. SDF-1, is also known to play a role in HIV-1 pathogenesis. The structures of SDF-1, determined by NMR spectroscopy have been shown to be monomeric while X-ray structures are dimeric. Biochemical data and in vivo studies suggest that dimerization is likely to be important for the function of chemokines. We report here the dynamics of SDF-1, determined through measurement of main chain 15N NMR relaxation data. The data were obtained at several concentrations of SDF-1, and used to determine a dimerization constant of ,5 mM for a monomer,dimer equilibrium. The dimerization constant was subsequently used to extrapolate values for the relaxation data corresponding to monomeric SDF-1,. The experimental relaxation data and the extrapolated data for monomeric SDF-1, were analyzed using the model free approach. The model free analysis indicated that SDF-1, is rigid on the nano- to picosecond timescale with flexible termini. Several residues involved in the dimer interface display slow micro- to millisecond timescale motions attributable to chemical exchange such as monomer,dimer equilibrium. NMR relaxation measurements are shown to be applicable for studying oligomerization processes such as the dimerization of SDF-1,. [source] Protein self-association in solution: The bovine , -lactoglobulin dimer and octamerPROTEIN SCIENCE, Issue 11 2003Michael Gottschalk Abstract We have used proton magnetic relaxation dispersion (MRD) to study the self-association of bovine , -lactoglobulin variant A (BLG-A) as a function of temperature at pH 4.7 (dimer,octamer equilibrium) and as a function of NaCl concentration at pH 2.5 (monomer,dimer equilibrium). The MRD method identifies coexisting oligomers from their rotational correlation times and determines their relative populations from the associated dispersion amplitudes. From MRD-derived correlation times and hydrodynamic model calculations, we confirm that BLG-A dimers associate to octamers below room temperature. The tendency for BLG-A dimers to assemble into octamers is found to be considerably weaker than in previous light scattering studies in the presence of buffer salt. At pH 2.5, the MRD data are consistent with an essentially complete transition from monomers in the absence of salt to dimers in 1 M NaCl. Because of an interfering relaxation dispersion from nanosecond water exchange, we cannot determine the oligomer populations at intermediate salt concentrations. This nanosecond dispersion may reflect intersite exchange of water molecules trapped inside the large binding cavity of BLG-A. [source] Expression, purification, crystallization and preliminary X-ray analysis of an archaeal protein homologous to plant nicotianamine synthaseACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2008Cyril Dreyfus In plants, nicotianamine synthase (NAS) plays a key role in metal homeostasis as it catalyzes the formation of nicotianamine, an important iron and nickel chelator and a precursor of plant phytosiderophores. Here, the crystallization of a protein from Methanothermobacter thermoautotrophicus (MTH675; referred to here as MtNAS) that appears to be homologous to plant NAS is reported. Purification of this protein showed a monomer,dimer equilibrium that could be displaced by using a reducing agent such as DTT. Crystals belonging to space group P212121 and containing dimers of MtNAS were grown by the vapour-diffusion method using polyethylene glycol 3350 as precipitant. A complete native X-ray data set was collected to 1.7,Å resolution at a synchrotron source. [source] | ||||||||||