Stoichiometric dissociation constant

STM image of glycogen 174 Stoichiometric dissociation constant 305 Stokes-Einstein equation 461 Stokes radius 109 Stomach ulcer 187 Stomata 30 Stop codons 236 Stopped flow technique 468 Stratum corneum 439 Strecker degradation 121 Strength of binding. See also Formation constants, Dissociation constants, Gibbs in metal complexes 307 Streptavidin 728 Stromelysins 627 Strontium 19... 

Clegg S. L. and Whitfield M. (1995) A chemical model of seawater including dissolved ammonia and the stoichiometric dissociation constant of ammonia in estuarine water and seawater from — 2 to 40 °C. Geochim. Cosmochim. Acta 59, 2403 -2421. 

Ion activity constants (thermod3mamic dissociation constants) and stoichiometric dissociation constants of acids. 

Ka is the true dissociation or ionization constant as distinguished from the stoichiometric dissociation constant... 

The constants in these expressions stand for the stoichiometric dissociation constants which, as we have seen, increase at first until a given ionic strength is attained, and then diminish. They would indicate that the pH of a solution of an acid salt is not independent of dilution, thus contradicting the conclusion of in-... 

We must state, however, that the thermodynamic dissociation constants have a relatively small practical importance. It is true that they remain constant with changing ionic strength but to use them it is necessary to know the activity coefficients of the several components at different electrolyte concentrations. The simple Debye-Huckel equation for computing activity coefficients is valid only at very small ionic strengths. At larger ionic strengths it is preferable to determine empirically the stoichiometric dissociation constants for various types of electrolytes. 

The stoichiometric dissociation constant and not the thermodynamic constant is calculated from the results of the kinetic method. The thermodynamic constant can then be computed from the stoichiometric constant by the method described in connection with the conductivity method (sub b). 

The first right-hand expression is written in activities, and this quotient gives the intrinsic dissociation constant. The second right-hand expression is made up of two factors, a quotient of (molar or molal) concentrations that may be called the stoichiometric dissociation constant, and a quotient of activity coefficients. All dissociation constants, association constants K = 1 /ATD), and solubility products in reference books are intrinsic constants. They apply to concentrations only if the solution is extremely dilute for all ionic species. In other cases, one has to know the activity coefficients. y0, i.e., y for a nonionic species, will mostly be close to unity, but y+ and y will generally be < 1, the more so for a higher ion concentration. One may define the free... 

J. Partanen, P. Juusola and P. Minkkinen, Determination of stoichiometric dissociation constants of lactic acid in aqueous salt solutions at 291.15 and 298.15 K, Fluid Phase Equilib., 2003, 204, 245-266. 

With a knowledge of the pH at the stoichiometric point and also of the course of the neutralisation curve, it should be an easy matter to select the appropriate indicator for the titration of any diprotic acid for which K1/K2 is at least 104. For many diprotic acids, however, the two dissociation constants are too close together and it is not possible to differentiate between the two stages. If K 2 is not less than about 10 7, all the replaceable hydrogen may be titrated, e.g. sulphuric acid (primary stage — a strong acid), oxalic acid, malonic, succinic, and tartaric acids. 

Polyprotic acids (or mixtures of acids, with dissociation constants AT, K2, and AT3) and strong bases. The first stoichiometric end point is given approximately... 

Zinc-finger proteins are also possible targets for bicyclams. All nu-cleocapsid proteins of known strains of retroviruses contain one or two copies of an invariant sequence, Cys-X2-Cys-X4-His-X4-Cys. Proteins with this sequence bind zinc stoichiometrically with dissociation constants of ca. 10-12M (377). Under physiological conditions, a 10-fold excess of EDTA removes only 50% of zinc from the zinc finger domain of HIV-1 nucleocapsid protein (378). 

Originally, the stoichiometric stability constants 6 for the lead and the cadmium complexes with chloride had been determined in NaCl-NaC104 solutions and it had been assumed that the NaCl was completely dissociated. The nominal ionic strength was one molal. The constants were later corrected by replacing the actual free chlorides for the total chlorides in the calculation of... 

Neither Fj nor F2 alone gave the characteristic fluorescence of fa and nicked fa in the presence of L-serine and pyridoxal phosphate. However, titration of a fixed amount of F2 with F2 gave rise to a fluorescence intensity 80-90% that of nicked fa at a stoichiometric ratio of Ft to F2. Moreover, both the excitation and emission spectra of the stoichiometric mixture were the same as for nicked fa. In addition, the same specific quenching of this fluorescence was shown in recombined Fj and F2 as in nicked fa. Further, the dissociation constants for L-serine and for indole were determined to be the same within experimental error for recombined Fj and F2, as for nicked fa. No significant differences were found between nicked fa and reconstituted Fj F2 in the intrinsic fluorescence of the aromatic residues, or in the sedimentation coefficients or the 200-250 nm CD spectra. From the foregoing independent lines of evidence, F2 and F2 combine to produce a structure very similar to that of nicked fa. 

To calculate microscopic constants from stepwise constants and tautomeric ratios, consider Eq. 6-76 in which [HP]a and [HP]B are the concentrations of the two tautomers and kj is the first stoichiometric or macroscopic dissociation constant for the diprotonated species H2P. 

In very dilute solutions the molar fraction -> activity of the solvent ( hs,mr) approaches unity, and the -> activity coefficients of the acid-base species approach 1, the conventional stoichiometric concentration dissociation constant of an acid H A in a given solvent HS is ... 

This equilibrium constant is expressed as the association constant which has dimensions (concentration)-1, in molar terms M-1. The dissociation constant KDiss is the reciprocal of and has dimensions of concentration (M). The objective of the following derivation is to obtain an equation of the form cAB = f(cA tot, cBjtot, fCA ), in which ci tot are the total or stoichiometric concentrations of the components i (which are known), in contrast to the quantity c in Eqn. 9.19, which are the free concentrations of the species in solution, which are not known. An equation of this form will enable us to calculate theoretical data. 

If the color of the base B differs from that of its conjugate acid BH+, it is possible by light absorption experiments to estimate the value of either cb or Cbh since the stoichiometric composition of the solution is known, the concentrations of all the four species cha, Ca", Cb and Cbh can be thus estimated, and value of K in equation (36), apart from the activity coefficient factor, can be calculated. In this way the approximate ratio of the dissociation constant of the acid HA to that of BH+ is obtained. The procedure is now repeated with an acid HA using the same base B, and from the two values of K the ratio of the dissociation constants of HA and HA can be found. This method can be carried through for a number of acids, new bases being used as the series is extended. ... 

For the titration of an acid HA in en (pATsH = 15.3) with overall dissociation constant of 10 with sodium aminoethoxide, calculate the pH at the following percentages of the stoichiometric amount of reagent added 0, 50, 90, 100, 110. Take the initial concentration of acid to be 0.01 M, neglect dilution, and assume that the salt has an overall dissociation constant of 10 and that pATj for sodium aminoethoxide is 5.84. 

Effective and inhibitory concentrations correspond to apparent dissociation constants of the host-guest complexes. These values can be quite different from the true Kd values. Particularly cautious interpretation is recommended for stoichiometric binding, molecular recognition may actually be much better than it appears in these cases [43-45]. Quantitative correlation of the values of JC50 and KD [44] is not common in the field of synthetic ion channels and pores. The Hill coefficient n... 

The relationship between the stoichiometric second dissociation constant Kzc and the thermodynamic constant Ku is given by... 

It is evident from the above that each of the amines of a group has a different dissociation constant and therefore a different basicity. I have found that this fact enables me to accomplish a separation of certain of the amines from the others. Even though each of the primary, secondary and tertiary amines in one group has a different basicity, it is not economically feasible with any process to separate those which have approximately the same basicity, for example, in the case of the methyl-amines, it is entirely practical to treat a mixture of the three amine salts with a quantity of alkali stoichiometrically equivalent to the trimethy-lamine present in the mixture and subsequently to boil out or otherwise remove the liberated trimethylamine. It is not, however, economically possible to obtain a sharp separation by treating the resulting residue of mono and dimethylamine saits with a further quantity of alkali equivalent to the monomethylamine and boil - the solution to obtain monomethylamine. The difference in basicity between the mono and dimethylamines is so small that good separation is not obtained. 

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