Search results for "sulfide"
showing 10 items of 388 documents
Reduced Apo-Fumarate Nitrate Reductase Regulator (ApoFNR) as the Major Form of FNR in Aerobically Growing Escherichia coli▿
2008
ABSTRACT Under anoxic conditions, the Escherichia coli oxygen sensor FNR (fumarate nitrate reductase regulator) is in the active state and contains a [4Fe-4S] cluster. Oxygen converts [4Fe-4S]FNR to inactive [2Fe-2S]FNR. After prolonged exposure to air in vitro, apoFNR lacking a Fe-S cluster is formed. ApoFNR can be differentiated from Fe-S-containing forms by the accessibility of the five Cys thiol residues, four of which serve as ligands for the Fe-S cluster. The presence of apoFNR in aerobically and anaerobically grown E. coli was analyzed in situ using thiol reagents. In anaerobically and aerobically grown cells, the membrane-permeable monobromobimane labeled one to two and four Cys res…
Stimulation of Fe-S cluster insertion into apoFNR by Escherichia coli glutaredoxins 1, 2 and 3 in vitro.
2004
Abstract The oxygen sensor fumarate nitrate reductase regu-lator (FNR) of Escherichia coli contains in the active (anaerobic)state a [4Fe–4S] 2þ cluster which is lost after exposure to O 2 .Inaerobically prepared apoFNR, or in FNR obtained by treatmentof [4Fe–4S] FNR with O 2 in vitro, intramolecular cysteinedisulfides are found, including the cysteine residues which serveas ligands for the Fe–S cluster. It is shown here that thereconstitution of [4Fe–4S] FNR from this form of aerobicapoFNR was preceded by a long lag phase when glutathione wasused as the reducing agent. Addition of E. coli glutaredoxins(Grx) 1, 2 or 3 decreased the lag phase greatly and stimulatedthe reconstitution rate slig…
Importance des variations latérales discrètes dans les apports détritiques, observées dans des faciès de rampe sédimentaire riches en matière organiq…
2017
17 pages; International audience; We studied a potential petroleum source rock deposited in a clastic-dominated ramp environment: the Argiles de Châtillon Formation (Kimmeridgian-Tithonian, Boulonnais area, northern France). The formation was deposited along a proximal-distal gradient on this ramp affected by synsedimentary fault movements. A sedimentological, mineralogical and geochemical study was conducted to decipher the distribution patterns of sedimentary parameters along such a depth increase over the ramp. It comes out that smectite distribution unexpectedly mimics the lateral depth evolution despite the good floatability of the mineral. It is also observed that the Argiles de Châti…
Organization of the major and minor capsid proteins in human papillomavirus type 33 virus-like particles.
1995
The organization of the major (L1) and minor (L2) proteins in the human papillomavirus capsid is still largely unknown. In this study we analysed the disulphide bonding between L1 proteins and the association of L2 proteins with capsomers using virus-like particles obtained in insect cells by co-expression of the L1 and L2 genes of human papillomavirus type 33. About 50% of the L1 protein molecules in these particles (1.29 g/cm3) formed disulphide-bonded trimers. Reduction of the intermolecular disulphide bonds by dithiothreitol (DTT) treatment caused disassembly of virus-like particles into capsomers. This indicates that disulphide bonds between capsomers at the threefold symmetry position…
Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions.
2015
Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L1) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L2), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [FeII(CH3CN)(L)]2+ (L = L1 (1); L2 (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [FeIV(O)(L)]2+ (L = L1 (3); L2 (4)), which were characterized by UV–vis spe…
Bio serves nano: biological light-harvesting complex as energy donor for semiconductor quantum dots.
2012
Light-harvesting complex (LHCII) of the photosynthetic apparatus in plants is attached to type-II core-shell CdTe/CdSe/ZnS nanocrystals (quantum dots, QD) exhibiting an absorption band at 710 nm and carrying a dihydrolipoic acid coating for water solubility. LHCII stays functional upon binding to the QD surface and enhances the light utilization of the QDs significantly, similar to its light-harvesting function in photosynthesis. Electronic excitation energy transfer of about 50% efficiency is shown by donor (LHCII) fluorescence quenching as well as sensitized acceptor (QD) emission and corroborated by time-resolved fluorescence measurements. The energy transfer efficiency is commensurable …
Molecular structures of Se(SCH3)2 and Te(SCH3)2 using gas-phase electron diffraction and ab initio and DFT geometry optimisations
2005
The molecular structures of Se(SCH3)2 and Te(SCH3)2 were investigated using gas-phase electron diffraction (GED) and ab initio and DFT geometry optimisations. While parameters involving H atoms were refined using flexible restraints according to the SARACEN method, parameters that depended only on heavy atoms could be refined without restraints. The GED-determined geometric parameters (rh1) are: rSe-S 219.1(1), rS-C 183.2(1), rC-H 109.6(4) pm; S-Se-S 102.9(3), Se-S-C 100.6(2), S-C-H (mean) 107.4(5), S-Se-S-C 87.9(20), Se-S-C-H 178.8(19)° for Se(SCH3)2, and rTe-S 238.1(2), rS-C 184.1(3), rC-H 110.0(6) pm; S-Te-S 98.9(6), Te-S-C 99.7(4), S-C-H (mean) 109.2(9), S-Te-S-C 73.0(48), Te-S-C-H 180.…
Reversibly stable thiopolyplexes for intracellular delivery of genes.
2006
Novel polyaspartamide non-viral carriers for gene therapy were synthesized by introducing, on the same polymer backbone, positively charged groups, for electrostatic interactions with DNA, and thiol groups for the formation of disulfide bridges between polymer chains. The introduction of thiols was aimed to have a vector with low redox potential sensitivity: disulfide crosslinking in fact, being stable in extracellular environment, allowed either to have stable complexes in plasma, that can protect DNA from metabolism, or to be reduced inside the cell, where the excess of glutathion in reduced form maintains a low redox potential. The consequent destabilization of the complex after disulfid…
Disulfide-crosslinked hyaluronan-gelatin hydrogel films: a covalent mimic of the extracellular matrix for in vitro cell growth
2003
A new disulfide crosslinking method was developed for the preparation of blended hyaluronan (HA)-gelatin hydrogels to form a synthetic, covalently linked mimic of the extracellular matrix (ECM). The HA and gelatin were chemically modified using 3,3′-dithiobis(propionic hydrazide) (DTP). After reduction with dithiothreitol (DTT), the thiol derivatives of HA (HA-DTPH) and gelatin (gelatin-DTPH) were obtained and characterized. To minimize interference with biological function, the degree of substitution of HA-DTPH and gelatin-DTPH was kept below 50%. Solutions of HA-DTPH and gelatin-DTPH in varying blends (20%, 40%, 60%, 80% gelatin) were prepared in 1% w/v NaCl and crosslinked by disulfide b…
Self-assembling and auto-crosslinkable hyaluronic acid hydrogels with a fibrillar structure
2008
Abstract A hyaluronic acid derivative bearing pendant l -benzoyl-cysteine portions (with a derivatization degree equal to 10 mol.%) was synthesized by linking N,N′-dibenzoyl- l -cystine to the polysaccharide and then reducing its disulfide bridge to thiol groups. The formation of π–π stacking interactions between the benzoyl moieties was studied by fluorescence spectroscopy as a function of polymer concentration and oxidation time. The efficiency of oxidation of thiol groups to disulfide bridges occurring in phosphate buffer pH 7.4, was determined by colorimetric assays. The hydrogel formed by means of oxidative crosslinking has shown the presence of fibrillar aggregates as detected by ligh…