ChemInform Abstract: KINETICS OF COMPLEXATION OF DIBENZO-18-CROWN-6 WITH STRONTIUM ION IN METHANOL AT -15°C STUDIED BY STOPPED FLOW TECHNIQUE

Initial rates of reaction for the above oxidation have been measured by a stopped-flow conductance method. Between pH 2 and 3.6, the initial rate of reaction, R, is given by the expression R{[HSO5-]+[SCN-]} = {kb+kc[H+]}[HSO5-]0[SCN-]20+ka[H+]-1[HSO5]20[SCN-]0 As pH increases, there is a transition to a pH-independent rate, first order in each thiocyanate and peroxomonosulphate concentrations.

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Metal Enolates – Enamines – Enol Ethers: How Do Enolate Equivalents Differ in Nucleophilic Reactivity?

Synthesis ◽

10.1055/s-0037-1611634 ◽

2019 ◽

Vol 51 (05) ◽

pp. 1157-1170 ◽

Cited By ~ 4

Author(s):

Artem Leonov ◽

Daria Timofeeva ◽

Armin Ofial ◽

Herbert Mayr

Keyword(s):

Rate Constants ◽

Correlation Equation ◽

Stopped Flow ◽

Quinone Methides ◽

Enol Ethers ◽

Reactivity Descriptors ◽

Silyl Enol Ethers ◽

Nucleophilic Reactivity ◽

Kinetics Of ◽

Least Squares Minimization

The kinetics of the reactions of trimethylsilyl enol ethers and enamines (derived from deoxybenzoin, indane-1-one, and α-tetralone) with reference electrophiles (p-quinone methides, benzhydrylium and indolylbenzylium ions) were measured by conventional and stopped-flow photometry in acetonitrile at 20 °C. The resulting second-order rate constants were subjected to a least-squares minimization based on the correlation equation lg k = s N(N + E) for determining the reactivity descriptors N and s N of the silyl enol ethers and enamines. The relative reactivities of structurally analogous silyl enol ethers, enamines, and enolate anions towards carbon-centered electrophiles are determined as 1, 107, and 1014, respectively. A survey of synthetic applications of enolate ions and their synthetic equivalents shows that their behavior can be properly described by their nucleophilicity parameters, which therefore can be used for designing novel synthetic transformations.

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Kinetics of sodium ion-induced calcium(2+) release in calcium(2+) loaded cardiac sarcolemmal vesicles: determination of initial velocities by stopped-flow spectrophotometry

Biochemistry ◽

10.1021/bi00537a033 ◽

1982 ◽

Vol 21 (8) ◽

pp. 1914-1918 ◽

Cited By ~ 25

Author(s):

Masaaki Kadoma ◽

Jeffrey Froehlich ◽

John Reeves ◽

John Sutko

Keyword(s):

Sodium Ion ◽

Stopped Flow ◽

Kinetics Of ◽

Sarcolemmal Vesicles

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Positive co-operative binding at two weak lysine-binding sites governs the Glu-plasminogen conformational change

Biochemical Journal ◽

10.1042/bj2850419 ◽

1992 ◽

Vol 285 (2) ◽

pp. 419-425 ◽

Cited By ~ 34

Author(s):

U Christensen ◽

L Mølgaard

Keyword(s):

Ligand Binding ◽

Binding Site ◽

Conformational Change ◽

Conformational Changes ◽

Binding Sites ◽

High Specificity ◽

Stopped Flow ◽

Protein Fluorescence ◽

Lysine Residues ◽

Kinetics Of

The kinetics of a series of Glu-plasminogen ligand-binding processes were investigated at pH 7.8 and 25 degrees C (in 0.1 M-NaCl). The ligands include compounds analogous to C-terminal lysine residues and to normal lysine residues. Changes of the Glu-plasminogen protein fluorescence were measured in a stopped-flow instrument as a function of time after rapid mixing of Glu-plasminogen and ligand at various concentrations. Large positive fluorescence changes (approximately 10%) accompany the ligand-induced conformational changes of Glu-plasminogen resulting from binding at weak lysine-binding sites. Detailed studies of the concentration-dependencies of the equilibrium signals and the rate constants of the process induced by various ligands showed the conformational change to involve two sites in a concerted positive co-operative process with three steps: (i) binding of a ligand at a very weak lysine-binding site that preferentially, but not exclusively, binds C-terminal-type lysine ligands, (ii) the rate-determining actual-conformational-change step and (iii) binding of one more lysine ligand at a second weak lysine-binding site that then binds the ligand more tightly. Further, totally independent initial small negative fluorescence changes (approximately 2-4%) corresponding to binding at the strong lysine-binding site of kringle 1 [Sottrup-Jensen, Claeys, Zajdel, Petersen & Magnusson (1978) Prog. Chem. Fibrinolysis Thrombolysis 3, 191-209] were observed for the C-terminal-type ligands. The finding that the conformational change in Glu-plasminogen involves two weak lysine-binding sites indicates that the effect cannot be assigned to any single kringle and that the problem of whether kringle 4 or kringle 5 is responsible for the process resolves itself. Probably kringle 4 and 5 are both participating. The involvement of two lysine binding-sites further makes the high specificity of Glu-plasminogen effectors more conceivable.

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The Kinetics of Peroxynitrite on Insulin Nitration Damage

10.21203/rs.3.rs-61724/v1 ◽

2020 ◽

Author(s):

Congxiao Zhang ◽

Fusheng Sun ◽

Congjiang Zhang ◽

Yunjing Luo

Keyword(s):

Activation Energy ◽

Biological Activity ◽

Glucose Metabolism ◽

Rate Constants ◽

The Body ◽

Stopped Flow ◽

Tyrosine Nitration ◽

Protein Nitration ◽

Physiological Conditions ◽

Kinetics Of

Abstract Background: Insulin is one of the most important versatile hormones that is central to regulating the energy and glucose metabolism in the body. There has been accumulating evidence supporting that diabetes was associated with peroxynitrite and protein nitration, and insulin nitration induced by peroxynitrite affected its biological activity. Methods: In this paper, the kinetics of insulin nitration by peroxynitrite in physiological conditions was studied by the stopped flow technique. Results: We determined the values of the reactive rate constants of peroxynitrite decomposition and peroxynitrite-induced tyrosine nitration in the presence of insulin. The activation energy of peroxynitrite decomposition and 3-nitrotyrosine yield in the presence of insulin is 48.8 kJ·mol−1 and 42.7 kJ·mol−1 respectively. Conclusions: It is inferred that the glutamate residue of insulin accelerated peroxynitrite decomposition and tyrosine nitration by reducing the activation energy of reactions. The results could be beneficial for exploring the molecular mechanism of diabetes and offering a new target for diabetes therapies.

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