Association-dissociation equilibrium

An inhibitory complex formed by preincubating Mg, phosphate and NaF binds to the enzyme and affects the association/dissociation equilibrium. 

Association-dissociation equilibrium, in micellization, 24 128, 129-131 Association for the Advancement of Medical Instrumentation (AAMI) Standards, 26 818-819 Association of American Feed Control Officials (AAFCO), 10 856 Nutrient Profiles, 10 857, 858-859t... 

Figure 12. Four state model of the hydration-mediated counterion—side chain association—dissociation equilibrium, of Mauritz. (Reprinted with permission from ref 107. Copyright 1982 American Chemical Society.)...

A term (also referred to as prior equilibrium ) denoting any reversible step that precedes an irreversible step or the rate-limiting step in a multistage reaction mechanism. The so-described reaction step must rapidly establish an equilibrium between its reactants and products. The first association/dissociation equilibrium leading to the formation of EX complex from E and S in the Michaelis-Menten treatment is an example of a preequilibrium. See Michaelis-Menten Kinetics... 

Association-dissociation equilibrium of artificial amphiphiles in either lipid layer may produce ion-conducting and nonconducting states, which may correspond to open and closed states, respectively. 

In connection with the subject of the relation between association state and kinetic order, it is germane to mention observations of Roovers and Bywater (45). They measured the dissociation constant for the tetramer , dimer case for polyiso-prenyllithium in benzene. The technique involved a study of the electronic spectra at 272 and 320 nm. If the process they measured can be directly related to the association-dissociation equilibrium, their results can be used to calculate the dissociation constant for the correct dimer monomer system. This value is ca. 2xl0-5 at 30.5°C. If this value is accepted, then the situation is encountered where the degree of dissociation of the polyisoprenyllithium chain ends varies from about 0.10 to... 

A conceptual difficulty In the theoretical description of Ionization equilibria is the distinction between "free" and "bound Ions (molecules or lonophores). Somewhat arbitrarily Onsager adopted Bjerrum s convention writing the distribution between free and bound ions as an association-dissociation equilibrium ... 

A relatively common feature of many problems involving molecular weight determination of biopolymers is that of association-dissociation equilibrium. Subunit structure of enzyme proteins is well recognized (1), and methods of dissociation of subunits to obtain monomer molecular weight are widely utilized (2). A previous paper described the application of an equilibrium gel partition method to the analysis of macromolecular association in a monomer-dimer case (3). The experimental parameters in a system utilizing the Sephadex series of gel filtra-... 

The concentration of Na cation, resulting from the dissociation of AOT, will be neglected, since it is at least a few times lower than the concentration of the electrolyte cation. The reassociation of the AOT adsorbed on the surface with the electrolytes cations is taken into account via the association—dissociation equilibrium, which leads to a surface charge density os given by30... 

II.G. Model Calculations. In what follows it will be shown that the general behavior discussed above is consistent with realistic calculations. An important parameter, which is however unknown, is the equilibrium constant of the association—dissociation equilibrium, Kv. The dissociation constant of the ion pair NaSQr was estimated to be Ku = 10 0 7 mol/dm3 = 0.1995 mol/dm3.11 Because of the repulsion among the headgroups on the interface, the dissociation constant is expected to be lower in the present case. In what follows, we will use Ku = 0.050 mol/dm3. For this value, the pressures at which the transitions from the common to the Newton black films occur are in agreement with the experiments of Exerowa et al.2... 

Temperature variation of the ESR spectrum of 4-cyanopyridine was interpreted as arising from interconversion of two distinct species. From the nature of the activation parameters, different solvation patterns for the ion-pair were inferred to be the cause rather than any association-dissociation equilibrium of the radical.100... 

Increasing the CO partial pressure decreases the hydro-formylation reaction rate and the amount of alkene isomerization side reactions (see Hydrogenation Isomerization ofAlkenes), while increasing the aldehyde linear to branched product ratio. Pino proposed that the apparent marked difference between HCo(CO)4-catalyzed hydroformylation at low and high CO partial pressures was due to the existence of two active catalyst species, HCo(CO)4 and HCo(CO)3, formed from the CO association/dissociation equilibrium shown in... 

Eisinger (1971) and Eisinger and Blumberg (1972) have developed the theory of gel zone electrophoresis of species in rapid association-dissociation equilibrium. It is clear that in a monomer-dimer self-... 

Benz R, Schmid A, Wagner W et al. (1989) Pore formation by the Escherichia coli hemolysin Evidence for an association-dissociation equilibrium of the poreforming aggregates. In Infect Immun 57 887-895. 

Figure 15.7 The rate of replication depends on the association-dissociation equilibrium. The data for time-dependent turnover raise the question whether fluorous interactions interfere with the association of the electrophilic fragment with the template thereby inhibiting catalysis [9]. See color plate 15.7.

In addition to n and n, which are the primary hydration numbers of cation and anion, respectively, and , the average number of water molecules bound in the ydrative associations of States 3 and 4-, are also computed using the model for the association-dissociation equilibrium between bound and unbound cations described previously. 

Bile salts carry extensive hydrophobic (hydrocarbon) portions in each molecule that attempt to reduce their contact with water (4). This is reflected in rapid, dynamic association-dissociation equilibrium to form self-aggregates or micelles as the total concentration of bile salt solute is increased (the CMC) [2-6]. Experimentally, micelles are undetectable in dilute solutions of the monomers, and are detected in increasing numbers and often size above the CMC [98]. Because bile salt micelles are often small (i.e., dimers) [5], and since self-aggregation continues to proceed in many cases with increasing concentration above the CMC [17,18,20,52,98], the detection of the lowest concentration at which the first aggregates form depends particularly upon the sensitivity of the experimental probes employed [98] and the physical-chemical conditions [3-5]. 

In the treatment by the mass action model, micellization is considered as an association-dissociation equilibrium of individual molecules or ions with micelles in the concentration range above CMC. 

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