Post-translational modification of Rhodococcus R312 and Comamonas NI1 nitrile hydratases

Nitrile hydratases (NHases) are industrially significant iron- and cobalt-containing enzymes used in the large-scale synthesis of acrylamide. Previous reports have shown that the active site peptides of NHases are post-translationally modified by oxidation of cysteine residues, and that these modifications are essential for catalysis. We report mass spectrometric evidence of the oxidation states of the active site cysteines in the iron coordination spheres of two iron-containing nitrile hydratases, namely R312 NHase from Rhodococcus rhodochrous strain R312 and NI1 NHase from Comamonas testosteroni. At least one of these cysteines is oxidised to a sulfinic acid (SO(2)H) and there is also evidence suggesting an additional oxidation to a sulfenic acid (SOH). This is the first evidence for the presence of these oxidation states for full-length NHases and for Fe-NHases from different microorganisms. The presence of these covalent modifications was confirmed by performing mass spectrometry on the active site peptide of R312 NHase, under native, reduced and carboxymethylated conditions. We also show the nitrosylation of the iron by mass spectrometry, as well as the release of NO by photoirradiation.     

Adsorption: an easy and efficient immobilisation of acetylcholinesterase on screen-printed electrodes

An amperometric biosensor based on acetylcholinesterase was constructed by simple adsorption of the enzyme on screen-printed electrodes (SPEs). This sensor was used to detect the inhibitory effects of organophosphorus and carbamate insecticides on acetylcholinesterase, and more particularly of chlorpyrifos ethyl oxon (CP-o). We demonstrate that enzyme adsorption on SPEs allows to obtain stable sensors that present good characteristics and are as efficient as other screen-printed biosensors based on covalent binding or entrapment of acetylcholinesterase (AChE).     

Synthese et structure du sulfate double MSbF2SO4 (M = Rb,Cs)

The crystal structure of RbSbF₂SO₄ has been determined on a single crystal (R = 0.078 for 710 reflections). The structure shows sulfate anions distorted by the SOSb bonds. The antimony atom is from an SbF₂ unit. This antimony dihalogen is from the family of the $\text{1}\text{1}$ compounds which are in MX₃SbX₃ (M = Al, Ga, In) (X = Cl, Br) systems.     

Compact interval spaces in which all closed subsets are homeomorphic to clopen ones,II

A topological spaceX whose topology is the order topology of some linear ordering onX, is called aninterval space. A space in which every closed subspace is homeomorphic to a clopen subspace, is called aCO space and a space isscattered if every non-empty subspace has an isolated point. We regard linear orderings as topological spaces, by equipping them with their order topology. IfL andK are linear orderings, thenL ^*, L+K, L · K denote respectively the reverse ordering ofL, the ordered sum ofL andK and the lexicographic order onL x K (so · 2=+). Ordinals are considered as linear orderings, and cardinals are initial ordinals. For cardinals , l 0, letL(K,)=K+1+*.Theorem: Let X be a compact interval scattered space. Then X is a CO space if and only if X is homeomorphic to a space of the form +1+_{1 L(K i i), where is any ordinal, n , for every ii},_i are regular cardinals and K_ii, and if n>0, then max({K_i:i相似文献   

The darcpluridata system: the 13C-n.m.r. data bank1

The capabilities of the DARC system are discussed and illustrated by the storage and retrieval functions of the ¹³C-n-m.r. data bank of the DARC PLURIDATA system. The data covered by the bank, as well as the input stream to the bank and validation of the spectra, are described. Particular stress is laid on the DARC structural retrieval system, which illustrates the interactive interrogation of a chemical data bank by means of the structural diagram of a molecule, i.e. the universal language in chemistry. The potential of the ¹³C-n.m.r. data bank in computer-aided structural elucidation is outlined.     

Low temperature magnetic structure of erbium iron garnet

The magnetic and crystallographic structure of erbium iron garnet {Er₃}[Fe₂](Fe₃)O₁₂ has been refined simultaneously from powder and single crystal neutron diffraction data. At 5 K the ferrimagnetic structure has a spin direction parallel to [100]. Magnetic moments of iron and erbium and canting angles for the erbium sublattices were derived in space groupI4₁/acd for 5 K<T<65 K. The magnetic moments of the two erbium sites are 6.9 _B and 4.3 _B at 5 K. An indication of further symmetry reduction of the magnetic structure from tetragonal to orthorhombic below 5 K is discussed.     

Fluorescence Study of Imidazoquinoxalines

The fluorescence properties of eleven novel derivatives based on the imidazo[1,2-a]quinoxaline structures have been studied. The absorption and emission spectra of these compounds have been recorded in dimethylsulfoxide solution. The phenyl substituting group on position 1 gives them particular properties thanks to the diverse hydroxy or methoxy decorating moieties, especially when they are multiplied or mixed. The investigated fluorescence auto-quenching revealed that the decreasing fluorescence intensity correlated only with the chemical structures of the aromatic compounds.