scholarly journals Kinetic and e.p.r. studies of cyanide and azide binding to the copper sites of dopamine (3,4-dihydroxyphenethylamine) β-mono-oxygenase

1984 ◽  
Vol 220 (2) ◽  
pp. 447-454 ◽  
Author(s):  
N J Blackburn ◽  
D Collison ◽  
J Sutton ◽  
F E Mabbs
Keyword(s):  
Competitive Inhibition ◽  
Charge Transfer Band ◽  
The Other ◽  
Native Enzyme ◽  
Interacting Species ◽  
Other Hand ◽  
Show Evidence ◽  
Simultaneous Decrease ◽  
Copper Sites ◽  
Kinetics Of

The kinetics of inhibition of dopamine (3,4-dihydroxyphenethylamine) beta-mono-oxygenase by cyanide (CN-) and azide (N3-) ions have been investigated by using steady-state methods. Both anions show complex non-competitive-inhibition patterns with respect to ascorbate, suggestive of anion binding at two different sites on the oxidized enzyme. To further investigate this finding, e.p.r. titrations of CN- and N3- binding to the 63Cu-reconstituted enzyme were carried out. Addition of approx. 2 equiv. of CN- to copper elicits a new signal with g = 2.217, g = 2.025, A = 17.0 mT characteristic of a copper (II)-cyano complex. Simulations show that this signal accounts for half the copper (II) in the enzyme. The remainder of the enzyme-bound copper is expressed by a signal close to, but not identical with, that of native enzyme. Further addition of CN- induces a simultaneous decrease in intensity of both of these signals so that their 1:1 ratio is maintained. Binding of N3-, on the other hand, changes the e.p.r. spectrum to a form different from either that of the native or CN‒ -treated enzyme, and integrates to 100% of the copper in the enzyme (g = 2.252, g = 2.050, A = 16.5 mT). Resolved superhyperfine structure is apparent in the g region. N3- binding is also accompanied by the appearance of a broad charge-transfer band centred at 387 nm. Neither 9 nor 35 GHz e.p.r. spectra show evidence for more than one (non-interacting) species of Cu(II) in native enzyme and N3- derivatives. The binding and reactivity of CN-, on the other hand, argues against independent copper sites in the enzyme.

THE ELECTRONIC STRUCTURES AND REACTIVITIES OF Mn(CO)5X COMPLEXES

1963 ◽  
Vol 41 (5) ◽  
pp. 1281-1288 ◽  
Author(s):  
Harry B Gray ◽  
Ernst Billig ◽  
Andrew Wojcicki ◽  
M. Farona
Keyword(s):  
Charge Transfer ◽  
Electronic Structures ◽  
Charge Transfer Band ◽  
The Other ◽  
Orbital Energy ◽  
Structural Description ◽  
Substitution Reactions ◽  
Energy Level Scheme ◽  
Kinetics Of ◽  
Orbital Energy Level

The bonding in Mn(CO)5X complexes is described in terms of molecular orbitals. The axial CO group is assumed to be bonded much more strongly to Mn than the other four CO groups. The molecular orbital energy level scheme thus derived successfully accounts for the principal features of the electronic spectra of Mn(CO)5X complexes in different solvents. The first charge transfer band is assigned as an n(Mn) → π*(CO) type transition. This n → π* assignment is supported by the fact that the maximum of the band for Mn(CO)5Br is shifted to higher energies on increasing the polarity of the solvents employed.Kinetic studies of Mn(CO)5X-14CO exchange reveal that the axial CO is more inert than the other four CO groups; also, the rates of 14CO exchange of the four equivalent CO groups in Mn(CO)5X complexes depend strikingly on the nature of the X− ligand. A consistent interpretation of the above results and the observed kinetics of some typical substitution reactions of Mn(CO)5X complexes is presented in terms of the derived electronic structural description.

Octahedral cobalt(III) complexes of the chloropentammine type. XXI. The preparation, properties, and reactions of some Chloro(amine)bis(ethylenediamine)cobalt(III) salts containing unidentate glycinenitrile and glycinamide as influencing ligands

1970 ◽  
Vol 23 (6) ◽  
pp. 1175 ◽  
Author(s):  
SC Chan ◽  
FK Chan
Keyword(s):  
Aqueous Solution ◽  
Pure State ◽  
The Other ◽  
Base Hydrolysis ◽  
Other Hand ◽  
Kinetics Of

Salts of one isomeric series of chloro(amine)bis(ethylenediamine)cobalt(111) type of cations have been prepared from trans-dichlorobis(ethy1enediamine)-cobalt(111) chloride by replacing one of its chloro ligands with either glycinenitrile or glycinamide. These complexes have been assigned a cis-configuration on the basis of spectral observations. For the glycinenitrile system, the cis-chloro(cyano-methylamine)bis(ethylenediamine)cobalt(111) cation rearranges to the trans-chloro(aminoacetonitrile) isomer in aqueous solution at rates very much higher than those for the aquation of both forms. This isomerization is retarded by acid and accelerated by base. The kinetics of base hydrolysis are also reported. On the other hand, for the glycinamide system, the corresponding isomerization proceeds at rates comparable to those of chloride release, the latter leading to the formation of the chelated N,O-glycinamidebis(ethylenediamine)cobalt(111) species. Consequently, it has not been possible to isolate the other linkage isomer in the pure state. Furthermore, although the aquo(glycinamide)bis(ethylenediamine)cobalt(111) species is not formed in non-basic spontaneous chloride release, its hydroxo counterpart can be readily obtained by base hydrolysis. The mechanistic implications of these observations are discussed.

The responses of language disordered children to indirect directives in varying contexts

1980 ◽  
Vol 1 (3) ◽  
pp. 295-306 ◽  
Author(s):  
Marilyn Shatz ◽  
Marsha A. Shulman ◽  
Deena K. Bernstein
Keyword(s):  
Early Response ◽  
The Other ◽  
Response Strategy ◽  
Linguistic Context ◽  
Response Behavior ◽  
Normal Children ◽  
Neutral Context ◽  
Other Hand ◽  
Early Action ◽  
Show Evidence

ABSTRACTLanguage disordered children's responses to sentences that can carry directive import were examined under varying contextual conditions. In the first experiment, sentences were presented in a neutral context; in the second experiment, two different kinds of sentences provided linguistic contexts for test sentences. Taken together, the results of the studies indicate that language disordered children are qualitatively much like normal children with regard to early response behavior. They show evidence of an early action response strategy and some ability to take context into account. On the other hand, they do appear to have more difficulty both in generating informing responses and in utilizing information from prior linguistic context. A possible reason for this latter deficit is suggested.

scholarly journals Non-Competitive Inhibition of Acetylcholinesterase by Bromotyrosine Alkaloids

2014 ◽  
Vol 9 (11) ◽  
pp. 1934578X1400901 ◽  
Author(s):  
Opeyemi J. Olatunji ◽  
Akintayo L. Ogundajo ◽  
Ibrahim A. Oladosu ◽  
Kanokwan Changwichit ◽  
Kornkanok Ingkaninan ◽  
...  
Keyword(s):  
Antiproliferative Activity ◽  
Binding Sites ◽  
Competitive Inhibition ◽  
The Other ◽  
Inhibiting Activity ◽  
Active Compounds ◽  
Other Hand ◽  
Hydrophobic Binding ◽  
Mcf 7

Fifteen bromotyrosine-derived alkaloids were isolated from the sponge Pseudoceratina cf. purpurea. The acetylcholinesterase-inhibiting activity of all the isolated compounds were examined; to purealidin Q, isoanomoian A, aplyzanzine A, and aplysamine 2 were active with IC50 values of 1.2, 70, 104, and 1.3 μM, respectively. On the other hand, antiproliferative activity against MCF-7 cells of aerophobin 1 gave an IC50 value of 0.8 μM. The Michaelis-Menten plots of the active alkaloids indicated that all the four compounds inhibited acetylcholinesterase in a non-competitive manner. The structures of the active compounds suggested that the N, N-dimethylaminopropyloxydibromotyramine moiety may play an important role in the enzyme-inhibiting activity, presumably on the anionic and hydrophobic binding sites.

scholarly journals The kinetics of the interaction of nitrous oxide and hydrogen

1924 ◽  
Vol 106 (737) ◽  
pp. 292-298 ◽  
Keyword(s):  
Nitrous Oxide ◽  
Preceding Paper ◽  
The Other ◽  
Kinetic Relation ◽  
Adsorbed Gas ◽  
Other Hand ◽  
The One ◽  
Related Reaction ◽  
Kinetics Of ◽  
Bimolecular Interaction

Of the three related reactions 2N 2 O = 2N 2 + O 2 ............ [1] 2H 2 + O 2 = 2H 2 O ..............[2] N 2 O + H 2 = N 2 + H 2 O ................[3] only the first two have hitherto been studied. The investigation of the kinetic relation of the third to the first two is the object of this paper. In the preceding paper it has been shown that the thermal decomposition of nitrous oxide into its elements is a homogeneous reaction in which practically every pair of nicrous oxide molecules react which collide under the condition that their joint energy exceeds about 58,000 cals, (for 2 gram molecules). This decomposition is uncatalysed by platinum or by rhodium. The combination of hydrogen and oxygen is, on the other hand, a reaction very dependent on catalytic influences. Bodenstein (‘Z. Physikal. Chem.,’ vol. 29, p. 665 (1899)) found that between 482° C. and about 600° C. the combination proceeds exclusively on the walls of a porcelain containing-vessel. Platinum, rhodium, and other metals have long been known to have a very pronounced catalytic action on a mixture of hydrogen and oxygen. Langmuir (‘Trans. Faraday Soc.,’ vol. 17, p. 621 (1922)) has studied the kinetics of the interaction of hydrogen and oxygen on the surface of a platinum wire, and finds that between 300° and 600° abs. the rate of combination is approximately proportional to the pressure of the oxygen and inversely to that of the hydrogen. There is now abundant evidence that catalytic reactions occur within a layer of adsorbed gas not more than a molecule or so deep, in immediate contact with the surface, and the interpretation of Langmuir’s results is that between 300° and 600° abs. the surface of the platinum is nearly completely covered with a layer of hydrogen and that reaction occurs when oxygen molecules enter gaps in this layer, the number of free spaces being easily shown to be inversely proportional to the pressure of the hydrogen. Turning now from the reactions [1] and [2] to the related reaction [3], the following questions present themselves, namely:— ( a ) whether nitrous oxide and hydrogen undergo a homogeneous bimolecular interaction at temperatures below that at which [1] takes place; ( b ) whether hydrogen and nitrous oxide interact catalytically on the surface of platinum. On the one hand, platinum becomes covered with a film of hydrogen which is activated for reaction [2], while on the other hand, platinum has no activating effect on nitrous oxide for reaction [1].

Triazene metabolism. I. The effect of substituents in the aryl group on the kinetics of enzyme-catalysed N-demethylation of 1-aryl-3,3-dimethyltriazenes

1981 ◽  
Vol 59 (12) ◽  
pp. 1234-1238 ◽  
Author(s):  
James R. P. Godin ◽  
Keith Vaughan ◽  
Kenneth W. Renton
Keyword(s):  
Liver Microsomes ◽  
The Other ◽  
Active Metabolites ◽  
Aryl Group ◽  
Effect Of Substituents ◽  
Formaldehyde Release ◽  
Other Hand ◽  
Order Of Magnitude ◽  
Nash Reagent ◽  
Kinetics Of

A series of antitumor dimethylaryltriazenes (ArN=N∙NMe2) have been studied with respect to enzyme catalysed N-demethylation by liver microsomes and the Km values determined by Lineweaver–Burk treatement. The substituent in the aryl group of the triazene does not significantly effect the magnitude of Km, which is of the same order of magnitude as the Km for aminopyrine. On the other hand, dimethyltriazenes appear to have lower Km values for demethylation than the structurally similar dimethylnitrosamines. Monomethyltriazenes, the proposed active metabolites of the dimethyltriazenes, do not undergo appreciable demethylation in the presence of microsomes and it appears that the dimethyltriazenes only demethylate once during metabolism. Spontaneous formaldehyde release from the hydroxymethyltriazene in the presence of the Nash reagent prevented an analogous study of the metabolism of these compounds.

scholarly journals Studies on Transformations of Hemophilus influenzae

1961 ◽  
Vol 45 (2) ◽  
pp. 205-228 ◽  
Author(s):  
Sol H. Goodgal
Keyword(s):  
Cell Concentration ◽  
The Other ◽  
Dna Molecules ◽  
Dna Preparation ◽  
Dna Concentration ◽  
Hemophilus Influenzae ◽  
Other Hand ◽  
Competent Cells ◽  
Kinetics Of

Unlinked transformations were demonstrated to occur by varying the multiplicity of DNA molecules taken up by competent cells. The number of doubles was directly proportional to the product of the frequency of singles for varying concentrations of cells. The kinetics of transformation to doubles and the effect of DNA concentration on double transformations were consistent with the concept that the cell must take up two molecules of DNA in order to be doubly transformed. Linked markers, on the other hand, were a constant fraction of the single transformation for variations in DNA or cell concentration, or time. The kinetics of transformation of linked markers was the same as for the kinetics of single transforming factors. It was, therefore, concluded that linked transformations involve interaction between the cell and a molecule of DNA carrying both markers. The frequency of transformation was found to be the same from resistance to sensitivity as from sensitivity to resistance for the markers streptomycin (S) and cathomycin (C). Purified DNAs, in general, show lower levels of linkage than crude DNA preparations, and for some crude preparations all the S markers were linked to C, suggesting that some dispersion, at least, was a result of DNA preparation. The inactivation of linked markers by heat, ultraviolet, and DNAase was studied.

143 Stimulated glycolysis is able to maintain ATP levels and motility of bull spermatozoa submitted to mitochondrial depolarisation

2020 ◽  
Vol 32 (2) ◽  
pp. 198
Author(s):  
J. Losano ◽  
J. Padín ◽  
I. Méndez-López ◽  
D. Angrimani ◽  
N. Montez ◽  
...  
Keyword(s):  
Atp Synthesis ◽  
The Other ◽  
Atp Levels ◽  
Other Hand ◽  
Significant Difference ◽  
Carbonyl Cyanide ◽  
Bovine Spermatozoa ◽  
Kinetics Of ◽  
Glucose Supplementation

Studies have reported the importance of mitochondria in sperm metabolism. However, for some species, glycolysis appears to be as essential as oxidative phosphorylation in sperm physiology. On the other hand, these mechanisms have not been fully elucidated for bovine spermatozoa. Therefore, the aim of this study was to evaluate the role of mitochondria and glycolysis in ATP synthesis and sperm kinetics of bovine spermatozoa. For this purpose, sperm from seven bovine epididymides (n=7) was collected and diluted to a concentration of 100×106 spermatozoamL−1 in Tyrode's albumin lactate pyruvate medium. Then, each sample was divided into 10 aliquots and evaluated in a 2×5 factorial design, with the first factor being the presence or absence of glucose (5mM) to stimulate glycolysis and the second factor being treatment with the mitochondrial uncoupler carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP; 0, 0.1, 0.3, 1, and 3 µM) to deplete mitochondrial ATP. Sperm samples were subjected to measurements of ATP levels using a luminescence technique (CellTiter-Glokit, Promega), with ATP levels measured in duplicate. In addition, sperm samples were subjected to computerised analysis of total and progressive motilities (ISAS, Proiser). Statistical analysis was performed using SAS (SAS Institute Inc.), where the interaction between the factors was analysed using PROC GLM and the comparison between groups was performed using means analysis of variance (least significant difference test). It was considered significant at 5%. Adenosine triphosphate was lower at FCCP concentrations of 0.3 µM (180.3±31.9nM), 1 µM (220.2±40.4nM), and 3 µM (272.3±70.4nM) than at 0 µM (control; 448.6±63.7nM) and 0.1 µM (422.4±41.5nM) in the absence of glucose. However, in the groups treated with FCCP supplemented with glucose, ATP concentrations did not differ among the groups (0 µM: 577.2±70.4 nM; 0.1 µM: 610.8±57.8 nM; 0.3 µM: 606.2±64.2 nM; 1 µM: 670.9±61.9 nM; 3 µM: 696.1±68.5nM). Additionally, total motility was lower in FCCP-treated groups without glucose supplementation. On the other hand, total motility increased in the groups treated with 0.3, 0.1, 1, and 3 µM FCCP supplemented with glucose. A similar effect was verified for progressive motility. Based on these results, we can suggest that glucose supplementation is able to maintain ATP levels and motility in bull sperm undergoing FCCP-induced mitochondrial depolarisation.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

The Cellular Origin in Atheromatous Lesion

1970 ◽  
Vol 28 ◽  
pp. 202-203
Author(s):  
T. M. Murad ◽  
H. A. I. Newman ◽  
K. F. Kern
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Rabbit Aorta ◽  
Mixed Population ◽  
The Other ◽  
Cellular Origin ◽  
Ultrastructural Studies ◽  
Atherosclerotic Lesions ◽  
Show Evidence ◽  
Early Lesion

The origin of lipid containing cells in atheromatous lesion has been disputed. Geer in his study on atheromatous lesions of rabbit aorta, suggested that the early lesion is composed mainly of lipid-laden macrophages and the later lesion has a mixed population of macrophages and smooth muscle cells. Parker on the other hand, was able to show evidence that the rabbit lesion is primarily composed of lipid-laden cells of smooth muscle origin. The above studies and many others were done on an intact lesion without any attempt of cellular isolation previous to their ultrastructural studies. Cell isolation procedures have been established for atherosclerotic lesions through collagenase and elastase digestion Therefore this procedure can be utilized to identify the cells involved in rabbit atheroma.

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