Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

d-Amino acid oxidase can oxidize the substrate to a ketoacid in the absence of oxygen. The stoichiometry of this reaction is precisely 1 molecule of keto acid for 1 molecule of enzyme, containing two flavin groups. Hence, the flavin must be in the semi-reduced free radical state. But these free radicals cannot be visualized by ESR spectroscopy because of closeness and strong interaction. After the acid denaturation of the protein the coenzyme is released as a semi-reduced free radical. An alternative method of registration is the transfer of the free radical state to an added excess of free flavin molecules. By both methods it is quantitatively determined that each flavin of the enzyme is reduced to a free radical. Therefore, we believe to have evidenced unambiguously that this enzymatic reaction proceeds via a free radical transition state.
Mol Biol (Mosk)
PMID:[The mechanism of action of d-amino acid oxidase. I. Evidence for a free radical mechanism of the reaction catalyzed b a dimeric form of the enzyme]. 0 43

Some physico-chemical properties of lecithin lyposomes and the effects of pH, temperature and ionic strength changes are studied by ESR using hydrophobic and hydrophylic nitroxyl radicals as spin probes. The structure differences between outer and inner layers of bilayer liposomes are observed using auxiliary water soluble paramagnetic complex and attributed tentatively to the different curvature signs of both layers. Lower estimates of transversal diffusion rates of both probes throught the membrane are obtained using exchange broadening technique and water soluble reducing agent. The limiting step in this diffusion is revealed, caused by the transport of a charged group of the diffusing molecule through the hydrophobic membrane space.
Mol Biol (Mosk)
PMID:[A study of the physico-chemical properties of lecithin membranes using hydrophobic and hydrophilic spin probes]. 0 47

D-Amino acid oxidase was shown to dissociate into subunits in 2 M urea retaining the catalytic activity. This makes possible the direct observation of ESR spectra of the intermediate radical state of the enzyme when interacting with the substrate. We have shown that these radicals are really observable. Using the reversibility of the reaction and an equilibrium shift the amount of radicals can be increased up to 10% of all flavin groups present. The dependence of the radicals concentration on the amount of substrate and product can be predicted. The theory is confirmed by experimental data.
Mol Biol (Mosk)
PMID:[Mechanism of action of D-amino acid oxidase. II. Evidence for the free radical mechanism of the reaction catalysed by the monomer form of the enzyme]. 3 48

The interaction of nitrogenase with spin labels of four types have been studied. Conclusion about the presence of two SH-groups in the nitrogenase active site (one in Mo-Fe-protein and one in the Fe-protein) have been drawn from the correlation between the degree of inhibition of nitrogenfixing activity by the labels derived from p-Cl-Hg-benzoate and degree of binding of these labels to the nitrogenase molecule. Anaysis of EPR spectra of spin-labeled nitrogenase at 77 degrees K and at room temperature have shown that the labels bind to the free SH-groups and interact with iron containing center (ICC) of nitrogenase through the exchange mechanism. Distance between SH-group and ICC have been found to be 12 A. Spin labels derived from isocyanide have been bound directly to ICC in amount of 6--10 labels per one nitrogenase molecule. Due to the exchange interaction between these labels they give the singlet ESR spectra both at 77 degrees and at room temperature which is characteristic for the closely disposed labels. From this fact a conclusion have been drawn about the cluster structure of ICC. The labels derived from iodoacetamide ana maleimide bind SH- and NH2-groups of nitrogenase molecules. Analysis of temperature dependence of the effective rotational frequency of this labels have revealed a conformational transition in nitrogenase molecule at 19 degrees C, that has made it possible to explain the break in the Arrenius plots of enzyme activity.
Mol Biol (Mosk)
PMID:[Study of the nitrogenase from Azotobacter vinelandii by the method of spin labels]. 17 70

The kinetics of the reaction of periodate oxidized oligonucleotides with polyacrylhydrazide gel was studied. The rate of the reaction is proportional to (see article), where M is the molecular weight of the oligonucleotide for the permeable gels. The rate of the reaction with given oligonucleotide decrease as the number of crosslinks in the gel matrix increase; a dramatic decrease of the rate occurs when oligonucleotides become too large to penetrate into the matrix. The rate of the reactions with short oligonucleotides does not depend upon the viscosity of the medium. ESR method revealed a considerable decrease of the rotational mobility of oligonucleotides captured by the gel matrix. It has been shown also that an increase of the number of cross-links leads to a decrease of the rotational mobility of the gel chains.
Mol Biol (Mosk)
PMID:[Effect of chain length of dialdehyde oligonucleotides on the rate of their interaction with the three-dimensional matrix of polyacrylamide gel]. 17 71

The effect of the cholinergic activator, phenyltrimethylammonium, on the ESR spectra of spin-labeled membrane bound acetylcholinesterase was studied; a reduction of maximal hyperfine splitting of the anisotropic ESR spectrum by 2 G was observed. The influence of phenyltrimethylammonium was prevented by the two cholinergic blocking agents d-tubocurarine and alpha-cobratoxine. The present results indicate that the conformation change of the esteratic site of membrane acetylcholinesterase is triggered by the binding of phenyltrimethylammonium to the cholinoreceptor site.
Mol Cell Biochem 1976 Dec 10
PMID:An ESR study of the postsynatpic membrane acetylcholinesterase of Torpedo marmorata electric organ. 18 29

Polarity of double and ternary water-nonelectrolyte systems at the component ratio, corresponding to a half-transition point of DNA from B to A form was evaluated from ESR spectra of a spin-probe. In all cases examined the isotropic super-fine splitting constant (aN) is the same with an accuracy of 0.05 gauss. Small differences in aN are well correlated with the concentration of the groups which are able to form hydrogen bonds with the nitroxide fragment of the radical. Thus, media polarity is a factor which determines the A--B equilibrium of DNA in solution.
Mol Biol (Mosk)
PMID:[Polarity of the environment as a factor determining DNA conformation]. 20 79

In subchloroplast fragments of photosystem II from Vicia faba, free from P700 contamination, a free-radical ESR signal (singlet of 9 G peak-to-peak line-width, g approximately 2,0025) appears under illumination in presence of silicomolybdate as electron acceptor. Using ESR-active electron donors and acceptors as well as conventional redox reagents Hill activity of preparations has been evaluated under different conditions. Evidences are presented that the light-induced dark-reversible silicomolybdate-dependent ESR signal is of the same origin as photobleaching centered at 680 nm which has been earlier interpreted as a result of P680 center of photosystem II oxydation. The relaxation properties of this paramagnetic center as measured by microwave power saturation are different from that of P700+-center in photosystem I.
Mol Biol (Mosk)
PMID:[Light-dependent paramagnetic center in photosystem 2 of higher plants]. 22 May 22

In pigment-protein complexes of photosynthetic reaction centres (RC's), extracted from chromatophore membranes of Rps. sphaeroides with sodium dodecylsulphate, functional activity and intramolecular mobility were studied as a function of temperature and hydration by use of the technique of optical absorbance and ESR spectroscopy. Over the studied temperature range from +20 to -120 degrees C and at a relative humidity (P/Ps) from 0.9 to 0.1, there observed a close interrelationship between reversible kinetic changes of direct and backward redox-reactions of the photo-reduced endogeneous acceptor of quinone nature and the effective parameter of the correlation time of the rotational diffusion of the hydrophobic spin probe as well as of spin labels chemically bound to SH- and COOH-groups of amino acid residues of the RC's protein. The findings support the view that the conformational dynamics in the RC controls the effectiveness of the primary processes of stabilization of photochemically separated charges.
Mol Biol (Mosk)
PMID:[Conformational mobility and functional activity of photosynthetic reaction centers of Rhodopseudomonas sphaeroides]. 22 May 25

The binding of ethidium bromide and acriflavin dyes with DNA modified with a spin-labelled analogue of ethylene imine has been studied. These spin-labels were shown to bind covalently to DNA, at the same time the number of the dye molecules bound is decreased without any changes in the binding constant. Analysis of ESR spectra of the samples in the frozen 50% water-glycerol solution at 77 degrees K for spin-labelled DNA has shown that addition of the dyes increases distance between the labels. This fact might be explained by an increase in DNA length upon formation of the complex with dye molecules.
Mol Biol (Mosk)
PMID:[Study of DNA-dye interaction by spin-labels]. 22 30


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