Comments on "Mach-Line Determination for Air in Dissociation Equilibrium"

1960 ◽  
Vol 27 (10) ◽  
pp. 796-797 ◽  
Author(s):  
Eldon L. Knuth
Keyword(s):  
Dissociation Equilibrium

Optimal Duration of the Preincubation Phase in Enzyme Inhibition Experiments

2020 ◽  
Author(s):  
Petr Kuzmic
Keyword(s):  
Enzyme Inhibition ◽  
Dose Response ◽  
Enzyme Inhibitor ◽  
Single Point ◽  
Association Rate ◽  
Weakly Bound ◽  
Inhibitor Complex ◽  
Dissociation Equilibrium ◽  
Optimal Duration ◽  
Algebraic Formula

This report describes an algebraic formula to calculate the optimal duration of the pre-incubation phase in enzyme-inhibition experiments, based on the assumed range of expected values for the dissociation equilibrium constant of the enzyme–inhibitor complex and for the bimolecular association rate constant. Three typical experimental scenarios are treated, namely, (1) single-point primary screening at relatively high inhibitor concentrations; (2) dose-response secondary screening of relatively weakly bound inhibitors; (3) dose-response screening of tightly-bound inhibitors.

Mucosal gastrin receptor. III. Regulation by gastrin

1980 ◽  
Vol 238 (2) ◽  
pp. G135-G140 ◽  
Author(s):  
K. Takeuchi ◽  
G. R. Speir ◽  
L. R. Johnson
Keyword(s):  
Serum Gastrin ◽  
Binding Capacity ◽  
Specific Binding ◽  
Equilibrium Constants ◽  
Biological Response ◽  
Liquid Diet ◽  
Regulatory Process ◽  
Membrane Preparation ◽  
Gastrin Receptor ◽  
Dissociation Equilibrium

Specific binding of 125I-labeled gastrin to rat gastric mucosal membranes was found to vary with serum gastrin levels. The dissociation equilibrium constants were not significantly different between receptor preparations. However, the binding capacities of the membrane preparations were directly correlated with serum gastrin levels. Fasting, feeding a liquid diet, and antrectomy significantly decreased serum gastrin and the concentrations of the gastrin receptor. Treatment of fasted and liquid-fed animals with pentagastrin prevented the decrease in receptors. Vagotomy increased both binding capacity and serum gastrin levels. These data indicate that gastrin stimulates the production of its own receptor. The upregulation of the gastrin receptor was evident if the binding capacity was expressed per milligram of protein, per microgram of DNA, or per amount of 125I-labeled choleragen bound to the same membrane preparation. This indicates that the biological response to gastrin is controlled in part by the regulation of the number of gastrin receptors present and that gastrin plays a role in this regulatory process.

TITRATIONS OF ORGANIC SOILS WITH STANDARD BASE: SOLUBILITY OF IONIZABLE FUNCTIONAL GROUPS AT 25 °C

1989 ◽  
Vol 69 (2) ◽  
pp. 313-325 ◽  
Author(s):  
DONALD S. GAMBLE
Keyword(s):  
Functional Groups ◽  
External Solution ◽  
Organic Soil ◽  
Organic Soils ◽  
Total Acid ◽  
Dissociation Equilibrium ◽  
Carboxylate Anions ◽  
Data Production ◽  
Standard Base ◽  
Automatic Titrator

The conversion of undissolved acidic functional groups into dissolved carboxylate anions has been monitored during potentiometric titration of a Typic Mesisol Peat at 25 °C. The analytical chemical calculations of total acid functional groups and of H+ dissociation equilibrium functions take the dissolution process into account. With 0.05 g of sample suspended in 20 mL of 0.1 N NaCl, the molarity of carboxylate anions in the external solution ranged from 4.3 × 10−4 M at 1 mL g−1 0.1 N NaOH, to 1.5 × 10−3 M at 6 mL g−1 0.1 N NaOH. The corresponding amounts of undissolved carboxyl groups were 5.2 × 10−4 and 1.0 × 10−4 mol g−1. Differential acid constants (KGA) for the undissolved carboxyls were 7.6 × 10−4 (σ 1.4 × 10−4) for αG < 0.02 (0.016 – 0.02) and 1.4 × 10−5 (σ 0.04 × 10−5) for αG > 0.026 (0.026 – 0.60). A substantial increase in productivity was achieved by means of an automatic titrator and a microcomputer with spreadsheet software. Types of data production and processing that were previously labor intensive have now become much more practical. Key words: Organic soils, organic matter solubility, organic soil carboxyls, organic soil ion exchange, organic soil titration, pH dependent solubility

Correlation Between Reduced Mass and Gibbs Energy Change of Reaction

2021 ◽  
Author(s):  
Masatoshi Kawashima
Keyword(s):  
Gibbs Energy ◽  
Bond Formation ◽  
Energy Change ◽  
Gibbs Energy Change ◽  
Positive Direction ◽  
Dissociation Equilibrium ◽  
Equilibrium Reactions ◽  
The Relationship ◽  
Good Agreement ◽  
Bond Formation Reactions

<p>The correlation between the Gibbs free energy change of reaction and the reduced mass was clarified. In the case of bond formation reactions, the computed Gibbs energy change of reaction increased in the positive direction as the reduced mass increased. In the case of dissociation equilibrium reactions, such as the dissociation of tetrahedral carbonyl addition compound, the computed Gibbs energy change of reaction also increased in the positive direction as the reducing mass increased, but the extent of the change was smaller than in the case of bond formation reactions. The results were in good agreement with those derived from the relationship between yield and reduced mass, indicating that was originated from the correlation between the Gibbs energy change and the reduced mass.</p>

«4 S» Polycyclic Aromatic Hydrocarbon Binding Protein: Further Characterization and Kinetic Properties

1987 ◽  
Vol 73 (3) ◽  
pp. 237-247 ◽  
Author(s):  
Maria Teresa Masucci ◽  
Antonella Petrillo ◽  
Vincenzo Sica
Keyword(s):  
Binding Protein ◽  
Equilibrium Constants ◽  
Binding Activity ◽  
Dissociation Rate ◽  
Maximum Activity ◽  
Partial Purification ◽  
Kinetic Properties ◽  
Order Kinetic ◽  
Dissociation Equilibrium ◽  
Polycyclic Aromatic

A protein that binds polycyclic aromatic hydrocarbons (PAHs) with high affinity and sediments in a sucrose gradient at 4 S has been described in rat liver cytosol. This « 4 S » PAH binding protein precipitates at a 40–60% ammonium sulfate saturation. This partial purification procedure allows assay of this protein by using purified 3H-benzo(a)pyrene (3H-BaP) as radioactive ligand and dextran-coated charcoal as adsorbent for unreacted 3H-BaP. The 3H-BaP binding activity measured as a function of pH shows its maximum activity between pH 7.3 and 10.5. The « 4 S » PAH binding protein is stable up to 42 °C even in the absence of the ligand. At 65 °C the binding sites for 3H-BaP are destroyed. The binding activity assayed as a function of protein concentration is linear between 0.4 and 2 mg/ml at 0 °C, whereas at 37 °C higher protein concentrations (4 mg/ml) can be reached. Exposure to guanidine-HCl (3 M) and urea (5 M) for 20 min at 4 °C inhibits the PAH binding completely to the « 4 S » protein. Quick dilution or dialysis does not restore the binding activity. The dissociation rate of the « 4 S » PAH binding protein measured in the presence of an excess of unlabeled ligand at 0 °C is biphasic and shows a two-step, first-order kinetic pattern. At 37 °C the dissociation rate is linear and faster, and is complete after 5 min of incubation. The association rate shows the same behavior: the binding is complete after 10 min at 0 °C, whereas at 37 °C the reaction is 10 times as fast. The dissociation equilibrium constants at 0 °C and 37 °C are respectively 2.45 × 10−9 M and 1.09×10−9 M. The high rates of association and dissociation of BaP to « 4 S » PAH binding protein were used to set up an assay to exchange radioactive 3H-BaP with cold BaP.

Aqueous nonelectrolyte solutions — Part XX: Formula of structure I methane hydrate, congruent dissociation melting point, and formula of the metastable hydrate

2003 ◽  
Vol 81 (12) ◽  
pp. 1443-1450 ◽  
Author(s):  
David N Glew
Keyword(s):  
Melting Point ◽  
Equilibrium Constant ◽  
Methane Hydrate ◽  
Equilibrium Constants ◽  
Stability Range ◽  
Congruent Melting Point ◽  
Quadruple Point ◽  
Dissociation Equilibrium ◽  
Metastable Structure ◽  
The Stability

Sixteen new measurements of high precision for structure I methane hydrate with water between 31.93 and 47.39 °C are shown to be metastable and exhibit higher methane pressures than found by earlier workers. Comparison of earlier measurements between 26.7 and 47.2 °C permit positive identification of the structure II and the structure I hydrates. Forty-nine equilibrium constants Kp(h1[Formula: see text]l1g) for dissociation of structure I methane hydrate into water and methane, 32 between –0.29 and 26.7 °C for the stable hydrate and 17 between 31.93 and 47.39 °C for the metastable hydrate, are best represented by a three-parameter thermodynamic equation, which indicates a standard error (SE) of 0.63% on a single Kp(h1[Formula: see text]l1g) determination. The congruent dissociation melting point C(h1l1gxm) of metastable structure I methane hydrate is at 47.41 °C with SE 0.02 °C and at pressure 505 MPa. The congruent equilibrium constant Kp(h1[Formula: see text]l1g) is 102.3 MPa with SE 0.2 MPa. ΔH°t(h1[Formula: see text]l1g) is 62 281 J mol–1 with SE 184 J mol–1, and the congruent formula is CH4·5.750H2O with SE 0.059H2O. At the congruent point, ΔV(h1[Formula: see text]l1g) is zero within experimental precision, and its estimate is 1.3 with SE 1.6 cm3 mol–1. The stability range of structure I methane hydrate with water extends from quadruple point Q(s1h1l1g) at –0.29 °C up to quadruple point Q(h1h2l1g) at 26.7 °C, and its metastability range with water extends from 26.7 °C up to the congruent dissociation melting point C(h1l1gxm) at 47.41 °C. Key words: methane hydrate, clathrate structure I, metastability range, dissociation equilibrium constant, formula, congruent melting point, metastability of structure I hydrate.

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