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Journal articles on the topic 'Steady-state dissociation constant'

Author: Grafiati

Published: 5 June 2025

Last updated: 2 August 2025

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1

Ikechukwu, I. Udema. "Derivation of steady-state first-order rate constant equations for enzyme-substrate complex dissociation, as well as zero-order rate constant equations in relation to background assumptions." GSC Biological and Pharmaceutical Sciences 21, no. 3 (2022): 175–89. https://doi.org/10.5281/zenodo.7654125.

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The maximum velocity (<em>V</em><sub>max</sub>) of catalysis and the substrate concentration ([<em>S</em><sub>T</sub>]) at half the <em>V</em><sub>max</sub>, the <em>K</em><sub>M</sub><em>,</em> are regarded as steady-state (SS) parameters even though they are the outcomes of zero-order kinetics (ZOK). The research was aimed at disputing such a claim with the following objectives: To: 1) carry out an overview of issues pertaining to the validity of assumptions; 2) derive the needed steady-state (SS) equations distinct from Michaelian equations that can be fitted to both experime

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2

Ikechukwu I. Udema. "Derivation of steady-state first-order rate constant equations for enzyme-substrate complex dissociation, as well as zero-order rate constant equations in relation to background assumptions." GSC Biological and Pharmaceutical Sciences 21, no. 3 (2022): 175–89. http://dx.doi.org/10.30574/gscbps.2022.21.3.0482.

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The maximum velocity (Vmax) of catalysis and the substrate concentration ([ST]) at half the Vmax, the KM, are regarded as steady-state (SS) parameters even though they are the outcomes of zero-order kinetics (ZOK). The research was aimed at disputing such a claim with the following objectives: To: 1) carry out an overview of issues pertaining to the validity of assumptions; 2) derive the needed steady-state (SS) equations distinct from Michaelian equations that can be fitted to both experimental variables and kinetic parameters; 3) calculate the SS first-order rate constant for the dissociatio

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3

HARWOOD, H. James, and Lorraine D. PELLARIN. "Kinetics of low-density lipoprotein receptor activity in Hep-G2 cells: derivation and validation of a Briggs–Haldane-based kinetic model for evaluating receptor-mediated endocytotic processes in which receptors recycle." Biochemical Journal 323, no. 3 (1997): 649–59. http://dx.doi.org/10.1042/bj3230649.

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The process of receptor-mediated endocytosis for receptors that recycle to the cell surface in an active form can be considered as being kinetically analogous to that of a uni-substrate, uni-product enzyme-catalysed reaction. In this study we have derived steady-state initial-velocity rate equations for this process, based on classical Briggs–Haldane and King–Altman kinetic approaches to multi-step reactions, and have evaluated this kinetic paradigm, using as a model system the low-density lipoprotein (LDL)-receptor-mediated endocytosis of the trapped label [14C]sucrose-LDL in uninduced, stead

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4

Rigney, E., T. J. Mantle, and F. M. Dickinson. "The kinetics of ox kidney biliverdin reductase in the pre-steady state. Evidence that the dissociation of bilirubin is the rate-determining step." Biochemical Journal 259, no. 3 (1989): 709–13. http://dx.doi.org/10.1042/bj2590709.

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When the production of bilirubin by biliverdin reductase was monitored at 460 nm by stopped-flow spectrophotometry a ‘burst’ was observed with a first-order rate constant at pH 8 of 20 s-1. The steady-state rate was established on completion of the ‘burst’. When the reaction was monitored at 401 nm there was no observed steady-state rate, but a diminished pre-steady-state ‘burst’ reaction was still seen with a rate constant of 22 s-1. We argue that the rate-limiting reaction is the dissociation of bilirubin from an enzyme.NADP+.bilirubin complex. With NADPH as the cofactor the hydride-transfer

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5

Shobukhov, A., and H. Koibuchi. "Dissociation and recombination in the electrolyte flow model." Journal of Physics: Conference Series 2090, no. 1 (2021): 012076. http://dx.doi.org/10.1088/1742-6596/2090/1/012076.

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Abstract We propose a one-dimensional model for the dilute aqueous solution of NaCl which is treated as an incompressible fluid placed in the external electric field. This model is based on the Poisson-Nernst-Planck system of equations, which also contains the constant flow velocity as a parameter and considers the dissociation and the recombination of ions. We study the steady-state solution analytically and prove that it is a stable equilibrium. Analyzing the numerical solutions, we demonstrate the importance of dissociation and recombination for the physical meaningfulness of the model.

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6

Kuwabara, T., S. Kobayashi, and Y. Sugiyama. "Kinetic analysis of receptor-mediated endocytosis of G-CSF derivative, nartograstim, in rat bone marrow cells." American Journal of Physiology-Endocrinology and Metabolism 271, no. 1 (1996): E73—E84. http://dx.doi.org/10.1152/ajpendo.1996.271.1.e73.

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To elucidate the mechanism of the receptor-mediated clearance of granulocyte colony-stimulating factor (G-CSF), we performed kinetic analyses of the receptor-mediated endocytosis (RME) processes using a human G-CSF derivative, nartograstim (NTG), and isolated rat bone marrow cells. The first-order rate constants involved in RME processes were obtained by computerized model fitting of the time courses of the ligand-receptor complex on both the cell surface and in the cell interior and the degradation products in the medium in the pulse-chase experiment. They were also calculated based on a kine

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7

Zaborska, W., M. Leszko, M. Kot, and A. Juszkiewicz. "The enthalpimetric determination of inhibition constants for the inhibition of urease by acetohydroxamic acid." Acta Biochimica Polonica 44, no. 1 (1997): 89–98. http://dx.doi.org/10.18388/abp.1997_4444.

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The effect of concentration of acetohydroxamic acid (AHA) on inhibition of jack bean urease in phosphate buffer, pH 7.0, at 25 degrees C, was studied. The measurements were performed at urease concentration of 2.5 mg/100 cm3 for concentrations of urea and AHA ranging in the range of 2-50 mmol dm-3 and 0.25-10 mmol dm-3, respectively. The reactions were monitored by two techniques: analytical and enthalpimetric. For the analytical technique the growth of ammonia concentration in the course of the reaction was determined. From the recorded progress curves the following parameters were calculated

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8

Chizzonite, R., T. Truitt, B. B. Desai, et al. "IL-12 receptor. I. Characterization of the receptor on phytohemagglutinin-activated human lymphoblasts." Journal of Immunology 148, no. 10 (1992): 3117–24. http://dx.doi.org/10.4049/jimmunol.148.10.3117.

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Abstract IL-12 is a 75-kDa heterodimeric cytokine composed of disulfide-bonded 35-kDa and 40-kDa subunits. Included among the biologic activities mediated by IL-12 is induction of proliferation of PHA-activated human PBL. The concentration of IL-12 required to stimulate maximum proliferation of PHA-activated lymphoblasts is 50 to 100 pM. In this study, highly purified 125I-labeled IL-12 (7 to 15 microCi/microgram; 50 to 100% bioactive) was used to characterize the receptor for IL-12 on 4-day PHA-activated lymphoblasts. The binding of 125I-labeled IL-12 to PHA-activated lymphoblasts was saturab

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9

Mendel, C. M. "Modeling thyroxine transport to liver: rejection of the "enhanced dissociation" hypothesis as applied to thyroxine." American Journal of Physiology-Endocrinology and Metabolism 257, no. 5 (1989): E764—E771. http://dx.doi.org/10.1152/ajpendo.1989.257.5.e764.

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Three models for the hepatic uptake of thyoxine (T4) from human plasma were considered: 1) uptake occurs exclusively via the pool of free T4 after spontaneous dissociation of T4-plasma-protein complexes, 2) uptake occurs primarily via the pool of bound T4 by the interaction of one or more binding proteins with the cell-surface membrane, and 3) uptake occurs primarily by "enhanced dissociation" of T4 from one or more of its binding proteins within the sinusoids. Each of these models was examined in relation to well-accepted unidirectional uptake and steady-state kinetics data that indicate that

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10

Rakowski, Robert F., David C. Gadsby, and Paul De Weer. "Single Ion Occupancy and Steady-state Gating of Na Channels in Squid Giant Axon." Journal of General Physiology 119, no. 3 (2002): 235–50. http://dx.doi.org/10.1085/jgp.20028500.

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The properties of the small fraction of tetrodotoxin (TTX)-sensitive Na channels that remain open in the steady state were studied in internally dialyzed voltage clamped squid giant axons. The observed Ussing flux ratio exponent (n′) of 0.97 ± 0.03 (calculated from simultaneous measurements of TTX-sensitive current and 22Na efflux) and nonindependent behavior of Na current at high internal [Na] are explained by a one-site (“1s”) permeation model characterized by a single effective binding site within the channel pore in equilibrium with internal Na ions (apparent equilibrium dissociation const

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11

Wictome, M., I. Henderson, A. G. Lee, and J. M. East. "Mechanism of inhibition of the calcium pump of sarcoplasmic reticulum by thapsigargin." Biochemical Journal 283, no. 2 (1992): 525–29. http://dx.doi.org/10.1042/bj2830525.

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The steady-state ATPase activity of sarcoplasmic-reticulum (Ca(2+)-Mg2+)-ATPase is inhibited by thapsigargin at a molar ratio of 1:1, with a dissociation constant for thapsigargin estimated to be in the sub-nanomolar range. In the presence of thapsigargin, only a single Ca2+ ion binds to the ATPase. Similarly, addition of thapsigargin to the ATPase incubated in the presence of Ca2+ results in the release of one of the two originally bound Ca2+ ions. As monitored by the fluorescence of nitrobenzo-2-oxa-1,3-diazole-labelled ATPase, thapsigargin appears to shift the transition between E1 and E2 c

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12

Tateishi, N., D. K. Kim, and N. Akaike. "Acetylcholine-activated ionic currents in parasympathetic neurons of bullfrog heart." Journal of Neurophysiology 63, no. 5 (1990): 1052–59. http://dx.doi.org/10.1152/jn.1990.63.5.1052.

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1. The electrical and pharmacologic properties of acetylcholine (ACh)-induced current (IACh) were studied in the parasympathetic neurons isolated from bullfrog heart with the use of the concentration-clamp technique, which allows intracellular perfusion and rapid change of external solution within 2 ms under the single-electrode voltage-clamp condition. 2. The IACh consisted of an initial transient peak component and a successive steady-state plateau component. Both currents increased in a sigmoidal fashion with increasing ACh concentration. The dissociation constant (Kd value) and the Hill co

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13

EIS, Christian, and Bernd NIDETZKY. "Substrate-binding recognition and specificity of trehalose phosphorylase from Schizophyllum commune examined in steady-state kinetic studies with deoxy and deoxyfluoro substrate analogues and inhibitors." Biochemical Journal 363, no. 2 (2002): 335–40. http://dx.doi.org/10.1042/bj3630335.

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Trehalose phosphorylase is a component of the α-d-glucopyranosyl α-d-glucopyranoside (α,α-trehalose)-degrading enzyme system in fungi and it catalyses glucosyl transfer from α,α-trehalose to phosphate with net retention of the anomeric configuration. The enzyme active site has no detectable affinity for α,α-trehalose in the absence of bound phosphate and catalysis occurs from the ternary complex. To examine the role of non-covalent enzyme—substrate interactions for trehalose phosphorylase recognition, we used the purified enzyme from Schizophyllum commune and tested a series of incompetent str

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14

VENNING, Jamie D., and J. B. JACKSON. "A shift in the equilibrium constant at the catalytic site of proton-translocating transhydrogenase: significance for a ‘binding-change’ mechanism." Biochemical Journal 341, no. 2 (1999): 329–37. http://dx.doi.org/10.1042/bj3410329.

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In mitochondria and bacteria, transhydrogenase uses the transmembrane proton gradient (δp) to drive reduction of NADP+ by NADH. We have investigated the pre-steady-state kinetics of NADP+ reduction by acetylpyridine adenine dinucleotide (AcPdADH, an analogue of NADH) in complexes formed from the two, separately prepared, recombinant, peripheral subunits of the enzyme: the dI component, which binds NAD+ and NADH, and the dIII component, which binds NADP+ and NADPH. In the stopped-flow spectrophotometer the reaction proceeds as a single-turnover burst of hydride transfer to NADP+ on dIII before

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15

Lassen, Niels A. "Neuroreceptor Quantitation in vivo by the Steady-State Principle Using Constant Infusion or Bolus Injection of Radioactive Tracers." Journal of Cerebral Blood Flow & Metabolism 12, no. 5 (1992): 709–16. http://dx.doi.org/10.1038/jcbfm.1992.101.

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The approaches hitherto used for measuring the kinetic constants Kd and Bmax of neuroreceptors in vivo all violate the steady state of the system. This complicates the kinetic analysis as approximations must be made, introducing errors of unknown magnitude. The present study presents the theory for designing experiments in which the steady state is preserved. It is based on maintaining a constant degree of receptor binding (occupancy) throughout the experiment. This is achieved by administering by prolonged intravenous infusion the non-radioactive ligand one wishes to study. The fraction of re

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16

Wierzchowski, Jacek, Agnieszka Bzowska, Katarzyna Stępniak, and David Shugar. "Interactions of Calf Spleen Purine Nucleoside Phosphorylase with 8-Azaguanine, and a Bisubstrate Analogue Inhibitor: Implications for the Reaction Mechanism." Zeitschrift für Naturforschung C 59, no. 9-10 (2004): 713–25. http://dx.doi.org/10.1515/znc-2004-9-1017.

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Abstract Interactions of calf spleen purine nucleoside phosphorylase (PNP) with a non-typical substrate, 8-azaguanine (8-azaG), and a bisubstrate analogue inhibitor, 9-(2-phosphonylmethoxyethyl)- 8-azaguanine (PME-azaG), were investigated by means of steady-state fluorescence spectroscopy. Both 8-azaG and PME-azaG form fluorescent complexes with the enzyme, and dissociation constants are comparable to the appropriate parameters (Km or Ki) obtained from kinetic measurements. PME-azaG inhibits both the phosphorolytic and synthetic pathway of the reaction in a competitive mode. The complex of 8-a

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17

Kah, M., and C. D. Brown. "Sensitivity analysis for the SimpleTreat model to simulate fate of chemicals in sewage treatment plants." Water Science and Technology 63, no. 9 (2011): 2052–60. http://dx.doi.org/10.2166/wst.2011.445.

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SimpleTreat 3.1 predicts the distribution and elimination of chemicals by sewage treatment. The model is used as the default calculation in EUSES 2.0 to estimate exposure concentration in the receiving water, soil and air. A sensitivity analysis was performed to rank input parameters according to their influence on model predictions. Triclosan was selected for the base case. The sewage flow, degradation rates and parameters describing the raw sewage were shown to be the most sensitive inputs. The pH and dissociation constant are very sensitive parameters when working with ionisable compounds.

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18

Shin, Hyeon-Gyu, and Zhe Lu. "Mechanism of the Voltage Sensitivity of IRK1 Inward-rectifier K+ Channel Block by the Polyamine Spermine." Journal of General Physiology 125, no. 4 (2005): 413–26. http://dx.doi.org/10.1085/jgp.200409242.

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IRK1 (Kir2.1) inward-rectifier K+ channels exhibit exceedingly steep rectification, which reflects strong voltage dependence of channel block by intracellular cations such as the polyamine spermine. On the basis of studies of IRK1 block by various amine blockers, it was proposed that the observed voltage dependence (valence ∼5) of IRK1 block by spermine results primarily from K+ ions, not spermine itself, traversing the transmembrane electrical field that drops mostly across the narrow ion selectivity filter, as spermine and K+ ions displace one another during channel block and unblock. If ind

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19

Luxon, B. A., D. C. Holly, M. T. Milliano, and R. A. Weisiger. "Sex differences in multiple steps in hepatic transport of palmitate support a balanced uptake mechanism." American Journal of Physiology-Gastrointestinal and Liver Physiology 274, no. 1 (1998): G52—G61. http://dx.doi.org/10.1152/ajpgi.1998.274.1.g52.

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Hepatic clearance of long-chain fatty acids is substantially faster in females than in males, a fact that may underlie known gender-related differences in lipoprotein metabolism and associated disease states. To further investigate the transport steps responsible for this difference, we used a novel method combining multiple-indicator dilution and steady-state measurements of palmitate extraction from albumin solutions. We found that cytoplasmic transport of palmitate is sufficiently slow (diffusion constants 9.0 and 5.9 × 10−9cm2/s for male and female liver, respectively) that the steady-stat

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20

Mendel, C. M., R. R. Cavalieri, and R. A. Weisiger. "Uptake of thyroxine by the perfused rat liver: implications for the free hormone hypothesis." American Journal of Physiology-Endocrinology and Metabolism 255, no. 2 (1988): E110—E119. http://dx.doi.org/10.1152/ajpendo.1988.255.2.e110.

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To investigate the mechanism by which thyroxine (T4) in plasma enters hepatic cells, we measured the rate constants for uptake of free T4 by the perfused rat liver and for dissociation of T4 from its plasma binding proteins. Quantitative autoradiography of liver lobules after perfusion with [125I]T4 indicated an apparent rat constant for removal of free T4 from the sinusoids of at least 1.1 +/- 0.2 s-1. Single-pass extraction of T4 from human serum was 10.6 +/- 1.7% at physiological flow rates (1 ml.min-1.g liver-1). Rate constants for dissociation of T4 from plasma binding proteins at 37 degr

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21

Efremov, Alexander M., Dmitry B. Murin, and Sergey V. Belyaev. "ON MECHANISMS OF INCREASING HCL DISSOCIATION DEGREE IN GLOW DISCHARGE PLASMA." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 61, no. 7 (2018): 62. http://dx.doi.org/10.6060/ivkkt.20186107.5697.

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The influence of initial compositions of the binary HCl+Ar and HCl+O2 gas mixtures on the hydrogen chloride dissociation kinetics in low temperature gas discharge plasma was investigated. The experiments were carried out under the conditions of direct current glow discharge at constant total gas pressure (100 Pa) and discharge current (25 mA). The data on electro-physical plasma parameters and plasma composition were obtained by modeling procedure based on the simultaneous solution of Boltzmann kinetic equation and the equations of chemical kinetics for neutral and charged species in a steady-

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22

Christ, George J., Brian Stone, and Arnold Melman. "Age-dependent alterations in the efficacy of phenylephrine-induced contractions in vascular smooth muscle isolated from the corpus cavernosum of impotent men." Canadian Journal of Physiology and Pharmacology 69, no. 7 (1991): 909–13. http://dx.doi.org/10.1139/y91-138.

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Steady-state contractile responses elicited by phenylephrine activation of the α1-adrenergic receptor subtype were studied in vascular smooth muscle strips isolated from the corpus cavernosum of impotent men. The dissociation constant of phenylephrine was determined by the method of partial irreversible receptor inactivation over a wide range of α1-adrenergic receptor alkylation levels. Statistical analysis of mean population values revealed a significantly greater mean efficacy for phenylephrine-induced contractions in older patients (60–73 years old) than in younger patients (40–59 years old

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23

Chang, Hangil, and Toshiro Fujita. "A kinetic model of the thiazide-sensitive Na-Cl cotransporter." American Journal of Physiology-Renal Physiology 276, no. 6 (1999): F952—F959. http://dx.doi.org/10.1152/ajprenal.1999.276.6.f952.

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The aim of this study was to construct a numerical model of the thiazide-sensitive Na-Cl cotransporter (TSC) that can predict kinetics of thiazide binding and substrate transport of TSC. We hypothesized that the mechanisms underlying these kinetic properties can be approximated by a state diagram in which the transporter has two binding sites, one for sodium and another for chloride and thiazide. On the basis of the state diagram, a system of linear equations that should be satisfied in the steady state was postulated. Numerical solution of these equations yielded model prediction of kinetics

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24

Rendall, Alan D., and Eduardo D. Sontag. "Multiple steady states and the form of response functions to antigen in a model for the initiation of T-cell activation." Royal Society Open Science 4, no. 11 (2017): 170821. http://dx.doi.org/10.1098/rsos.170821.

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The aim of this paper is to study the qualitative behaviour predicted by a mathematical model for the initial stage of T-cell activation. The state variables in the model are the concentrations of phosphorylation states of the T-cell receptor (TCR) complex and the phosphatase SHP-1 in the cell. It is shown that these quantities cannot approach zero and that the model possesses more than one positive steady state for certain values of the parameters. It can also exhibit damped oscillations. It is proved that the chemical concentration which represents the degree of activation of the cell, that

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25

Caplow, Michael, John Shanks, and Bruna Pegoraro Brylawski. "Concerning the location of the GTP hydrolysis site on microtubules." Canadian Journal of Biochemistry and Cell Biology 63, no. 6 (1985): 422–29. http://dx.doi.org/10.1139/o85-061.

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The kinetics for GTP hydrolysis associated with microtubule assembly with microtubular protein has been analyzed under reaction conditions where tubulin–GDP does not readily assemble into microtubules. The GTPase rate is only slightly faster during the time when net microtubule assembly occurs, as compared with steady state. The slightly slower steady-state GTPase rate apparently results from GDP product inhibition, since the progressive decrease in the rate can be quantitatively accounted for using the previously determined GTP dissociation constant and the Ki value for GDP. Since the GTPase

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26

Veenstra, R. D. "Voltage-dependent gating of gap junction channels in embryonic chick ventricular cell pairs." American Journal of Physiology-Cell Physiology 258, no. 4 (1990): C662—C672. http://dx.doi.org/10.1152/ajpcell.1990.258.4.c662.

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The dependence of macroscopic gap junctional conductance (Gj) on transjunctional voltage (Vj) was studied in paired myocytes after enzymatic dissociation of 7-day-old embryonic chick ventricles. The membrane voltage of both cells was independently controlled by separate patch-clamp circuits in the whole cell configuration. Two distinctive unitary junctional conductances were identified in recordings from seven different cell pairs. The larger channel had a mean conductance of 166 +/- 37 pS (n = 6 pairs), whereas a second channel averaged 58 +/- 10 pS (n = 3). Instantaneous Gj remained linear o

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27

Senn, N., and R. P. Garay. "Regulation of Na+ and K+ contents in rat thymocytes." American Journal of Physiology-Cell Physiology 257, no. 1 (1989): C12—C18. http://dx.doi.org/10.1152/ajpcell.1989.257.1.c12.

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A modified nystatin technique allowed the investigation of the initial rate of Na+ efflux as a function of internal Na+ content under steady-state conditions in rat thymocytes. This kinetic study showed that 1) ouabain-sensitive Na+ efflux as a function of internal Na+ can be adjusted by a three-sites kinetic model, with a maximal pump rate of 581 +/- 79 mmol.l cells-1.h-1 and an apparent dissociation constant for internal Na+ of 10.0 +/- 1.0 mmol/l cells (mean +/- SE of 3 experiments), 2) bumetanide-sensitive Na+ efflux was extremely low compared with the pump efflux (approximately 1%), and 3

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TANG, Shiao-Shek, and Gu-Gang CHANG. "Kinetic mechanism of octopus hepatopancreatic glutathione transferase in reverse micelles." Biochemical Journal 315, no. 2 (1996): 599–606. http://dx.doi.org/10.1042/bj3150599.

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Octopus glutathione transferase (GST) was enzymically active in aerosol-OT [sodium bis-(2-ethylhexyl)sulphosuccinate]/iso-octane reverse micelles albeit with lowered catalytic constant (kcat). The enzyme reaction rate was found to be dependent on the [H2O]/[surfactant] ratio (ωo) of the system with maximum rate observed at ωo 13.88, which corresponded to vesicles with a core volume of 64 nm3. According to the physical examinations, a vesicle of this size is barely large enough to accommodate a monomeric enzyme subunit. Dissociation of the enzyme in reverse micelles was confirmed by cross-linki

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29

Zhang, Xiao-Dong, and Tsung-Yu Chen. "Amphiphilic Blockers Punch through a Mutant CLC-0 Pore." Journal of General Physiology 133, no. 1 (2008): 59–68. http://dx.doi.org/10.1085/jgp.200810005.

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Intracellularly applied amphiphilic molecules, such as p-chlorophenoxy acetate (CPA) and octanoate, block various pore-open mutants of CLC-0. The voltage-dependent block of a particular pore-open mutant, E166G, was found to be multiphasic. In symmetrical 140 mM Cl−, the apparent affinity of the blocker in this mutant increased with a negative membrane potential but, paradoxically, decreased when the negative membrane potential was greater than −80 mV, a phenomenon similar to the blocker “punch-through” shown in many blocker studies of cation channels. To provide further evidence of the punch-t

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30

Kuznetsova, Aleksandra A., Timofey E. Tyugashev, Irina V. Alekseeva, Nadezhda A. Timofeyeva, Olga S. Fedorova, and Nikita A. Kuznetsov. "Insight into the mechanism of DNA synthesis by human terminal deoxynucleotidyltransferase." Life Science Alliance 5, no. 12 (2022): e202201428. http://dx.doi.org/10.26508/lsa.202201428.

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Terminal deoxynucleotidyltransferase (TdT) is a member of the DNA polymerase X family that is responsible for random addition of nucleotides to single-stranded DNA. We present investigation into the role of metal ions and specific interactions of dNTP with active-site amino acid residues in the mechanisms underlying the recognition of nucleoside triphosphates by human TdT under pre–steady-state conditions. In the elongation mode, the ratios of translocation and dissociation rate constants, as well as the catalytic rate constant were dependent on the nature of the nucleobase. Preferences of TdT

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31

Wong, Dean F., Albert Gjedde, Henry N. Wagner, et al. "Quantification of Neuroreceptors in the Living Human Brain. II. Inhibition Studies of Receptor Density and Affinity." Journal of Cerebral Blood Flow & Metabolism 6, no. 2 (1986): 147–53. http://dx.doi.org/10.1038/jcbfm.1986.28.

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A method for estimating receptor density ( Bmax) in the living human brain by positron emission tomography was exemplified by a ligand, 3- N-[11C]methylspiperone ([11C]NMSP), that binds to D2 dopamine receptors with high affinity. The ligand binds essentially irreversibly (i.e., with very little dissociation) to the receptors during the 2-h scanning period. Transfer constants were estimated at steady state. In a previous article, we presented a method for the determination of k3, the rate of binding of the labeled ligand. In the present work, we varied k3 by reducing the number of available re

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32

Nettleton, R. E. "On the relation between thermodynamic temperature and kinetic energy per particle." Canadian Journal of Physics 72, no. 3-4 (1994): 106–12. http://dx.doi.org/10.1139/p94-017.

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In a computer simulation of a steady state in a fluid far from equilibrium, one needs to calculate temperature that is held constant. In classical thermodynamics and the local equilibrium approximation to nonequilibrium thermodynamics, T = TK ≡ (2/3Nκ) [Formula: see text], where [Formula: see text] is the kinetic energy, T is the temperature recorded by a thermometer in thermal equilibrium with the system. In extended thermodynamics, TK – T is of the order of squares of the heat and particle fluxes, shear-rate, or chemical reaction rate. Explicit estimates are made here of TK – T for binary is

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33

Sugihara, Izumi. "Activation and Two Modes of Blockade by Strontium of Ca2+-activated K+ Channels in Goldfish Saccular Hair Cells." Journal of General Physiology 111, no. 2 (1998): 363–79. http://dx.doi.org/10.1085/jgp.111.2.363.

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Effects of internal Sr2+ on the activity of large-conductance Ca2+-activated K+ channels were studied in inside-out membrane patches from goldfish saccular hair cells. Sr2+ was approximately one-fourth as potent as Ca2+ in activating these channels. Although the Hill coefficient for Sr2+ was smaller than that for Ca2+, maximum open-state probability, voltage dependence, steady state gating kinetics, and time courses of activation and deactivation of the channel were very similar under the presence of equipotent concentrations of Ca2+ and Sr2+. This suggests that voltage-dependent activation is

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34

Lassen, N. A., P. A. Bartenstein, A. A. Lammertsma, et al. "Benzodiazepine Receptor Quantification in vivo in Humans Using [11C]Flumazenil and PET: Application of the Steady-State Principle." Journal of Cerebral Blood Flow & Metabolism 15, no. 1 (1995): 152–65. http://dx.doi.org/10.1038/jcbfm.1995.17.

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Carbon-11-labeled flumazenil combined with positron emission tomography (PET) was used to measure the concentration ( Bmax) of the benzodiazepine (Bz) receptor in the brain and its equilibrium dissociation constant ( KD) for flumazenil in five normal subjects. The steady-state approach was used injecting the tracer as a bolus of high specific activity. In each subject two studies were carried out. The first study was performed at essentially zero receptor occupancy, the tracer alone study. The second study was performed at a steady-state receptor occupancy of about 50%, achieved by a prolonged

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35

Colombo, R., A. Milzani, P. Contini, and I. Dalle Donne. "Effects of lithium ions on actin polymerization in the presence of magnesium ions." Biochemical Journal 274, no. 2 (1991): 421–25. http://dx.doi.org/10.1042/bj2740421.

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In spite of the abundant literature, questions on the biological action of Li+ are far from being answered. In the present paper we demonstrate that modification of the salt composition of the medium for actin polymerization, by gradually replacing K+ with Li+, leads to a dose-related change in the time course of actin assembly. The presence of Li+ influences actin polymerization in vitro by enhancing nucleation and decreasing critical monomer concentration at steady state. Furthermore, Li+ stabilizes actin polymers mainly by lowering the absolute value of the dissociation rate constant (K-) a

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36

Pollard, T. D. "Rate constants for the reactions of ATP- and ADP-actin with the ends of actin filaments." Journal of Cell Biology 103, no. 6 (1986): 2747–54. http://dx.doi.org/10.1083/jcb.103.6.2747.

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I measured the rate of elongation at the barbed and pointed ends of actin filaments by electron microscopy with Limulus sperm acrosomal processes as nuclei. With improvements in the mechanics of the assay, it was possible to measure growth rates from 0.05 to 280 s-1. At 22 degrees C in 1 mM MgCl2, 10 mM imidazole (pH 7), 0.2 mM ATP with 1 mM EGTA or 50 microM CaCl2 or with EGTA and 50 mM KCl, the elongation rates at both ends have a linear dependence on the ATP-actin concentration from the critical concentration to 20 microM. Consequently, over a wide range of subunit addition rates, the rate

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37

Larivière, Richard, and Ernesto L. Schiffrin. "Effects of monovalent and divalent cations and of guanine nucleotides on binding of vasopressin to the rat mesenteric vasculature." Canadian Journal of Physiology and Pharmacology 65, no. 6 (1987): 1171–81. http://dx.doi.org/10.1139/y87-185.

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The rat mesenteric vasculature contains high affinity binding sites specific for [3H]Arg8-vasopressin which mediate its vasoconstrictor action. We have investigated the in vitro effect of monovalent and divalent cations and guanine nucleotides on the interactions between [3H]Arg8-vasopressin and its receptor in this preparation. Binding was increased by divalent cations from fourfold in the presence of Mg2+ at 5 mM to ninefold in the presence of Mg2+ at 5 mM. The potency order of divalent cations to increase binding was Mn2+ > Co2+ > Ni2+ > Mg2+ > Ca2+ ≈ control without cations. Ad

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38

Markwardt, F., and G. Isenberg. "Gating of maxi K+ channels studied by Ca2+ concentration jumps in excised inside-out multi-channel patches (myocytes from guinea pig urinary bladder)." Journal of General Physiology 99, no. 6 (1992): 841–62. http://dx.doi.org/10.1085/jgp.99.6.841.

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Currents through maxi K+ channels were recorded in inside-out macro-patches. Using a liquid filament switch (Franke, C., H. Hatt, and J. Dudel. 1987. Neurosci, Lett. 77:199-204) the Ca2+ concentration at the tip of the patch electrode ([Ca2+]i) was changed in less than 1 ms. Elevation of [Ca2+]i from less than 10 nM to 3, 6, 20, 50, 320, or 1,000 microM activated several maxi K+ channels in the patch, whereas return to less than 10 nM deactivated them. The time course of Ca(2+)-dependent activation and deactivation was evaluated from the mean of 10-50 sweeps. The mean currents started a approx

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39

Schilstra, M. J., P. M. Bayley, and S. R. Martin. "The effect of solution composition on microtubule dynamic instability." Biochemical Journal 277, no. 3 (1991): 839–47. http://dx.doi.org/10.1042/bj2770839.

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The exchange of tubulin dimer into steady-state microtubules was studied over a range of solution conditions, in order to assess the effects of various common buffer components on the dynamic instability of microtubules. In comparison with standard buffer conditions (100 mM-Pipes buffer, pH 6.5, containing 0.1 mM-EGTA, 1.8 mM-MgC12 and 1 M-glycerol), the rate and extent of exchange, and thus of dynamic instability, are suppressed by increasing the concentration of glycerol above 2 M. Exchange is enhanced by the addition of further Mg2+ (up to 17 mM) or by the addition of Ca2+ (up to 0.4 mM). P

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40

Forman, Stuart A., and Douglas E. Raines. "Nonanesthetic Volatile Drugs Obey the Meyer-Overton Correlation in Two Molecular Protein Site Models." Anesthesiology 88, no. 6 (1998): 1535–48. http://dx.doi.org/10.1097/00000542-199806000-00018.

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Background Nonanesthetic volatile compounds fail to inhibit movement in response to noxious stimulation at concentrations predicted to induce anesthesia from their oil-water partitioning. Thus they represent tools to determine whether molecular models behave like the targets that mediate in vivo anesthetic actions. The effects of volatile anesthetics and nonanesthetics were examined in two experimental models in which anesthetics interact directly with proteins: the pore of the nicotinic acetylcholine receptor and human serum albumin. Methods Wild-type mouse muscle nicotinic receptors and rece

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41

Tyacke, R. J., J. L. Harwood, and R. A. John. "Properties of the pyridoxaldimine form of glutamate semialdehyde aminotransferase (glutamate-1-semialdehyde 2,1-aminomutase) and analysis of its role as an intermediate in the formation of aminolaevulinate." Biochemical Journal 293, no. 3 (1993): 697–701. http://dx.doi.org/10.1042/bj2930697.

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Glutamate semialdehyde aminotransferase (glutamate-1-semialdehyde 2,1-aminomutase; EC 5.4.3.8) was converted into its pyridoxaldimine form by exhaustive replacement of endogenous pyridoxamine phosphate with pyridoxal phosphate. The isomerization of glutamate 1-semialdehyde to 5-aminolaevulinate by this form of the enzyme followed an accelerating time course which indicated that the enzyme initially had no activity but was converted into the active pyridoxamine phosphate form in an exponential process characterized by a rate constant (k) of 0.027 s-1. The pyridoxaldimine form of the enzyme was

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KHAN, Yamin M., Anthony P. STARLING, J. Malcolm EAST, and Anthony G. LEE. "The mechanism of inhibition of the Ca2+-ATPase of skeletal-muscle sarcoplasmic reticulum by the cross-linker o-phthalaldehyde." Biochemical Journal 317, no. 2 (1996): 439–45. http://dx.doi.org/10.1042/bj3170439.

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Labelling the Ca2+-ATPase of skeletal-muscle sarcoplasmic reticulum with o-phthalaldehyde (OPA) results in loss of ATPase activity at a 1:1 molar ratio of label to ATPase. The affinity of the ATPase for Ca2+ is unaffected, as is the E1/E2 equilibrium constant. The rate of dissociation of Ca2+ from the Ca2+-bound ATPase is also unaffected and Mg2+ increases the rate of dissociation, as for the unlabelled ATPase. Effects of Mg2+ on the fluorescence intensity of the ATPase labelled with 4-(bromomethyl)-6,7-dimethoxycoumarin are also unaffected by labelling with OPA, consistent with the fluorescen

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43

Hilgemann, D. W., S. Matsuoka, G. A. Nagel, and A. Collins. "Steady-state and dynamic properties of cardiac sodium-calcium exchange. Sodium-dependent inactivation." Journal of General Physiology 100, no. 6 (1992): 905–32. http://dx.doi.org/10.1085/jgp.100.6.905.

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Sodium-calcium exchange current was isolated in inside-out patches excised from guinea pig ventricular cells using the giant patch method. The outward exchange current decayed exponentially upon activation by cytoplasmic sodium (sodium-dependent inactivation). The kinetics and mechanism of the inactivation were studied. (a) The rate of inactivation and the peak current amplitude were both strongly temperature dependent (Q10 = 2.2). (b) An increase in cytoplasmic pH from 6.8 to 7.8 attenuated the current decay and shifted the apparent dissociation constant (Kd) of cytoplasmic calcium for second

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44

Logan, Jean, Joanna S. Fowler, Nora D. Volkow, et al. "Graphical Analysis of Reversible Radioligand Binding from Time—Activity Measurements Applied to [N-11C-Methyl]-(−)-Cocaine PET Studies in Human Subjects." Journal of Cerebral Blood Flow & Metabolism 10, no. 5 (1990): 740–47. http://dx.doi.org/10.1038/jcbfm.1990.127.

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A graphical method of analysis applicable to ligands that bind reversibly to receptors or enzymes requiring the simultaneous measurement of plasma and tissue radioactivities for multiple times after the injection of a radiolabeled tracer is presented. It is shown that there is a time t† after which a plot of f t0ROI( t') dt'/ROI( t) versus f t0 Cp( t') dt'/ROI( t) (where ROI and Cp are functions of time describing the variation of tissue radioactivity and plasma radioactivity, respectively) is linear with a slope that corresponds to the steady-state space of the ligand plus the plasma volume,

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45

KAPOOR, Mili, P. L. Swarna MUKHI, Namita SUROLIA, K. SUGUNA, and Avadhesha SUROLIA. "Kinetic and structural analysis of the increased affinity of enoyl-ACP (acyl-carrier protein) reductase for triclosan in the presence of NAD+." Biochemical Journal 381, no. 3 (2004): 725–33. http://dx.doi.org/10.1042/bj20040228.

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The binding of enoyl-ACP (acyl-carrier protein) reductase from Plasmodium falciparum (PfENR) with its substrates and inhibitors has been analysed by SPR (surface plasmon resonance). The binding of the substrate analogue crotonoyl-CoA and coenzyme NADH to PfENR was monitored in real time by observing changes in response units. The binding constants determined for crotonoyl-CoA and NADH were 1.6×104 M−1 and 1.9×104 M−1 respectively. Triclosan, which has recently been demonstrated as a potent antimalarial agent, bound to the enzyme with a binding constant of 1.08×105 M−1. However, there was a 300

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WANG, Weichi, Stéphanie NOËL, Michel DESMADRIL, Jacques GUÉGUEN, and Thierry MICHON. "Kinetic evidence for the formation of a Michaelis–Menten-like complex between horseradish peroxidase compound II and di-(N-acetyl-l-tyrosine)." Biochemical Journal 340, no. 1 (1999): 329–36. http://dx.doi.org/10.1042/bj3400329.

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The formation of a reversible adsorption complex between a dimer of N-acetyl-L-tyrosine [di-(N-acetyl-ʟ-tyrosine), (NAT)2] and horseradish peroxidase (HRP) compound II (CII) was demonstrated using a kinetic approach. A specific K value (0.58 mM) was deduced for this step from stopped-flow measurements. The dimerization of the dipeptide Gly-Tyr was analysed at the steady state and compared with (NAT)2 dimerization [(NAT)2 → (NAT)4]. A saturation of the enzyme was observed for both substrates within their range of solubility. In each case the rate of dimerization reflected the rate-limiting step

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47

Iannetta, Danilo, Rafael de Almeida Azevedo, Daniel A. Keir, and Juan M. Murias. "Establishing the V̇o2 versus constant-work-rate relationship from ramp-incremental exercise: simple strategies for an unsolved problem." Journal of Applied Physiology 127, no. 6 (2019): 1519–27. http://dx.doi.org/10.1152/japplphysiol.00508.2019.

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The dissociation between constant work rate of O2 uptake (V̇o2) and ramp V̇o2 at a given work rate might be mitigated during slowly increasing ramp protocols. This study characterized the V̇o2 dynamics in response to five different ramp protocols and constant-work-rate trials at the maximal metabolic steady state (MMSS) to characterize 1) the V̇o2 gain (G) in the moderate, heavy, and severe domains, 2) the mean response time of V̇o2 (MRT), and 3) the work rates at lactate threshold (LT) and respiratory compensation point (RCP). Eleven young individuals performed five ramp tests (5, 10, 15, 25,

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48

Laruelle, Marc, Anissa Abi-Dargham, Mohammed S. AI-Tikriti, et al. "SPECT Quantification of [123I]Iomazenil Binding to Benzodiazepine Receptors in Nonhuman Primates: II. Equilibrium Analysis of Constant Infusion Experiments and Correlation with in vitro Parameters." Journal of Cerebral Blood Flow & Metabolism 14, no. 3 (1994): 453–65. http://dx.doi.org/10.1038/jcbfm.1994.56.

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In vivo benzodiazepine receptor equilibrium dissociation constant, KD, and maximum number of binding sites, Bmax, were measured by single photon emission computerized tomography (SPECT) in three baboons. Animals were injected with a bolus followed by a constant i.v. infusion of the high affinity benzodiazepine ligand [123I]iomazenil. Plasma steady-state concentration and receptor–ligand equilibrium were reached within 2 and 3 h, respectively, and were sustained for the duration (4–9 h) of the experiments (n = 15). At the end of the experiments, a receptor saturating dose of flumazenil (0.2 mg/

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49

Ahn, Hye Sook, Sung Eun Kim, Bok Hee Choi, et al. "Calcineurin-independent inhibition of KV1.3 by FK-506 (tacrolimus): a novel pharmacological property." American Journal of Physiology-Cell Physiology 292, no. 5 (2007): C1714—C1722. http://dx.doi.org/10.1152/ajpcell.00258.2006.

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The interaction of FK-506 with KV1.3, stably expressed in Chinese hamster ovary cells, was investigated with the whole cell patch-clamp technique. FK-506 inhibited KV1.3 in a reversible, concentration-dependent manner with an IC50 of 5.6 μM. Rapamycin, another immunosuppressant, produced effects that were similar to those of FK-506 (IC50 = 6.7 μM). Other calcineurin inhibitors (cypermethrin or calcineurin autoinhibitory peptide) alone had no effect on the amplitude or kinetics of KV1.3. In addition, the inhibitory action of FK-506 continued, even after the inhibition of calcineurin activity. T

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Yang, Guangwei, Jimin Wang, Yao Cheng, et al. "Mechanism of Inhibition of Human Immunodeficiency Virus Type 1 Reverse Transcriptase by a Stavudine Analogue, 4′-Ethynyl Stavudine Triphosphate." Antimicrobial Agents and Chemotherapy 52, no. 6 (2008): 2035–42. http://dx.doi.org/10.1128/aac.00083-08.

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ABSTRACT 2′,3′-Didehydro-3′-deoxy-4′-ethynylthymidine (4′-Ed4T), a recently discovered nucleoside reverse transcriptase (RT) inhibitor, exhibits 5- to 10-fold-higher activity against human immunodeficiency virus type 1 (HIV-1) and less cytotoxicity than does its parental compound d4T (stavudine). Using steady-state kinetic approaches, we have previously shown that (i) 4′-ethynyl-d4T triphosphate (4′-Ed4TTP) inhibits HIV-1 RT more efficiently than d4TTP does and (ii) its inhibition efficiency toward the RT M184V mutant is threefold less than that toward wild-type (wt) RT. In this study we used

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