Home About us Contact
|
Home About us Contact | ||
|
|
||
Soluble Complexes (soluble + complex)
Selected AbstractsAgrobacterium type IV secretion is a two-step process in which export substrates associate with the virulence protein VirJ in the periplasmMOLECULAR MICROBIOLOGY, Issue 5 2002Mario Pantoja Summary Type IV secretion systems are virulence determinants in many bacteria and share extensive homology with many conjugal transfer systems. Although type IV systems and their homologues have been studied widely, the mechanism by which substrates are secreted remains unclear. In Agrobacterium, we show that type IV secretion substrates that lack signal peptides form a soluble complex in the periplasm with the virulence protein VirJ. Additionally, these proteins co-precipitate with constituents of the type IV transporter: the VirB pilus and the VirD4 protein. Our findings suggest that the substrate proteins localized to the periplasm may associate with the pilus in a manner that is mediated by VirJ, and suggest a two-step process for type IV secretion in Agrobacterium. Our analyses of protein,protein interactions in a variety of mutant backgrounds indicate that substrates are probably secreted independently of one another. [source] Complexes of Bidentate Phosphane Selenide Ligands with Mesitylenetellurenyl Iodide and with Tellurium Diiodide,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2006Cristian G. Hrib Abstract Bis(diphenylphosphanyl)methane diselenide (dppmSe2, 1) and bis(diphenylphosphanyl)ethane diselenide (dppeSe2, 2) reacted with 2 equiv. Br2 or I2 to form the insoluble solid products, dppm(SeX2)2 (X = Br, 3; X = I, 4) and dppe(SeX2)2 (X = Br, 5; X = I, 6). However, using the iodine-like electrophile mesitylenetellurenyl iodide (MesTeI, 7), fairly soluble complexes, dppmSe2[Te(I)Mes]2 (8) and dppeSe2[Te(I)Mes]2 (9), were obtained. Complexes 8 and 9 contain two T-shaped (10-Te-3) Se,Te(Mes),I moieties bridged by dppm or dppe; solid 9 exhibits intermolecular soft,soft interactions between approximately linear Se,Te,I units. In a side reaction accompanying the crystallisation of complex 8, or by the reaction of 1 with Te and I2, a chelate complex dppmSe2TeI2 (10) was formed. Fortuitously, a crystal of the related compound dppeSe2TeI2 (11) was also obtained. In 10, a square planar cis -Se2TeI2 group is part of a six-membered ring, and 11 is a coordination polymer with trans -Se2TeI2 moieties bridged by dppe. Averaged 31P- and 77Se NMR signals including 77Se,31P couplings, together with broad 125Te NMR singlets indicate phosphane selenide ligand exchange in solution, that is, the kinetically labile behaviour of complexes 8 and 9. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Small heat shock protein Hsp27 prevents heat-induced aggregation of F-actin by forming soluble complexes with denatured actinFEBS JOURNAL, Issue 22 2007Anastasia V. Pivovarova Previously, we have shown that the small heat shock protein with apparent molecular mass 27 kDa (Hsp27) does not affect the thermal unfolding of F-actin, but effectively prevents aggregation of thermally denatured F-actin [Pivovarova AV, Mikhailova VV, Chernik IS, Chebotareva NA, Levitsky DI & Gusev NB (2005) Biochem Biophys Res Commun331, 1548,1553], and supposed that Hsp27 prevents heat-induced aggregation of F-actin by forming soluble complexes with denatured actin. In the present work, we applied dynamic light scattering, analytical ultracentrifugation and size exclusion chromatography to examine the properties of complexes formed by denatured actin with a recombinant human Hsp27 mutant (Hsp27,3D) mimicking the naturally occurring phosphorylation of this protein at Ser15, Ser78, and Ser82. Our results show that formation of these complexes occurs upon heating and accompanies the F-actin thermal denaturation. All the methods show that the size of actin,Hsp27-3D complexes decreases with increasing Hsp27-3D concentration in the incubation mixture and that saturation occurs at approximately equimolar concentrations of Hsp27-3D and actin. Under these conditions, the complexes exhibit a hydrodynamic radius of ,,16 nm, a sedimentation coefficient of 17,20 S, and a molecular mass of about 2 MDa. It is supposed that Hsp27-3D binds to denatured actin monomers or short oligomers dissociated from actin filaments upon heating and protects them from aggregation by forming relatively small and highly soluble complexes. This mechanism might explain how small heat shock proteins prevent aggregation of denatured actin and by this means protect the cytoskeleton and the whole cell from damage caused by accumulation of large insoluble aggregates under heat shock conditions. [source] Potentiometric studies on the interaction between superoxide dismutase and hyaluronic acidJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009Yaofeng Fan Abstract The formation process of soluble complexes and insoluble aggregates between superoxide dismutase (SOD) and hyaluronic acid (HA) was studied using quasielastic light scattering and turbidimetric titration. The electrostatic binding between them was investigated in detail through potentiometric titration and turbidimetric titration carried out from high to low pH. Turbidimetric titration was used to determine the specific pH values at which soluble complex formation was initiated (pHc) and phase separation occurred (pH,). An increase of the ionic strength causes a decrease of pHc and pH,. With the increase of HA concentrations, pH, increases but pHc does not vary. The formed "salt bridges" between (SOD) and COO, (HA) result in the formation of stable SOD-HA complexes and even aggregates. The necessary condition of electrostatic binding was also given for protein-acidic polyelectrolyte systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] The role of Bi3+ -complex ion as the stabilizer in electroless nickel plating processAICHE JOURNAL, Issue 4 2009K. Wang Abstract Bi3+ -complex ion is presented here as a less toxic stabilizer for use in electroless nickel plating (ENP) to replace the existing Pb2+ ion stabilizer. The asymmetric derivatives of EDTA are identified to be a type of coordination ligands that can combine with Bi3+ ions to form soluble complexes in the acidic ENP solution. In the ENP system studied the Bi3+ -complex ion displays a critical stabilizer concentration of about 10,5 mol/L, that is, the percolation concentration over which the ENP rate drops sharply. Besides the experimental measurement, deposition rates of both Ni and P are also simulated by using a kinetic model that has been derived from the double electric layer theory. The Bi3+ -complex ion, behaving like conventional Pb2+ ion, stabilizes ENP bath through the chemical replacement reaction at the surface of Ni deposition layer and results in a passive plating surface. This investigation also verifies the properties of the EN deposit, which are insignificantly affected by the length of service time of the plating solution by employing Bi3+ -complex ion stabilizer. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Interaction of silicic acid with poly(1-vinylimidazole)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2006V. V. Annenkov Abstract Poly(1-vinylimidazole) reacts with silicic acid and poly(silicic acid), giving rise to water-soluble complexes and insoluble composites because of hydrogen bonding. The composition, structure, and morphology of the obtained products have been studied with elemental analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The main direction of the reaction depends not only on the initial ratio of the components, concentration, and pH but also on the sequence of the reagent mixing: the presence of poly(1-vinylimidazole) macromolecules during the formation of silicic acid stabilizes soluble complexes, which precipitate with an excess of H4SiO4 only. These soluble complexes may serve as a pattern of particles responsible for the transport of silicic acid in diatom algae and other organisms that assimilate silicon from the environment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 820,827, 2006 [source] Oxidative polymerization of N -vinylcarbazole in polymer matrixPOLYMER INTERNATIONAL, Issue 6 2001Belkis Ustamehmeto Abstract A new class of soluble conductive poly(N -vinylcarbazole) (PVCz) compounds has been developed by oxidative matrix polymerization of N -vinylcarbazole (NVCz) by Ce(IV) in the presence of poly(ethylene glycol) (PEG). PEG was found to be a more suitable matrix with which to obtain a stable homogenous ternary complex solution when compared with poly(acrylic acid) (PAA) and poly(vinylpyrrolidone) (PVP). The role of PEG, NVCz and Ce(IV) concentration, order of component addition, the structure of the polymer matrix, molecular weight of polymer and the effect of solvent have been investigated. Obtaining soluble PEG,Ce(III),PVCz ternary complexes was shown by cyclic voltammetric measurements, and the initial rate of formation NVCz cation radicals as calculated using UV,visible spectrophotometry. Advantageously with these soluble complexes, conductivities could be measured both in solution and in the solid state. © 2001 Society of Chemical Industry [source] | |||||||||||||