The dissociation rate constants for hydrogen fluoride dimers are calculated using the YL method, proposed by Yao and Lin (Yao, L.; Mebel, A. M.; Lu, H. F.; Neusser, H. J.; Lin, S. H. J. Phys. Chem. A 2007, 111, 6722). The dividing surface method and RRKM theory are also used to obtain pseudo-transition states and rate constants, respectively. For the dissociation of HF dimers, the anharmonic ra...

Metal dissociation constants for glyoxalase I from human erythrocytes were determined by use of nitrilotriacetic acid as a metal buffer. The constants for Zn2+, Co2+, Mn2+, and Mg2+ were (2.7 +/- 0.3) X 10(-11) M, (3.0 +/- 0.8) X 10(-10) M, (4.9 +/- 0.5) X 10(-9) M, and (1.0 +/- 0.2) X 10(-6) M, respectively, demonstrating that the natural cofactor, Zn2+, has the highest affinity for the apopro...

The biopharmaceutical profile of a compound depends directly on the dissociation constants of its acidic and basic groups, commonly expressed as the negative decadic logarithm pKa of the acid dissociation constant (Ka). The acid dissociation constant (also protonation or ionization constant) Ka is an equilibrium constant defined as the ratio of the protonated and the deprotonated form of a comp...

Autophosphorylation of Ca2+/calmodulin (CaM)-dependent protein kinase II (CaM-kinase II) induces a striking >1,000-fold increase in its affinity for CaM, which has been called CaM trapping. Two peptides modeled after the CaM binding domain of CaM-kinase II were previously shown to kinetically resemble CaM binding to phosphorylated and dephosphorylated forms of the enzyme, thus providing a model...

The cDNA for soybean leghemoglobin a (Lba) was cloned from a root nodule cDNA library and expressed in Escherichia coli. The crystal structure of the ferric acetate complex of recombinant wild-type Lba was determined at a resolution of 2.2 A. Rate constants for O2, CO and NO binding to recombinant Lba are identical with those of native soybean Lba. Rate constants for hemin dissociation and auto...

For an N-protic acid–base system, the set of nonlinear equations (i.e., mass action and balance laws) provides a simple analytical solution/formula for any integer N ? 1. The approach is applicable general case zwitterionic acids HNA+Z (e.g., amino acids, NTA, EDTA), which includes (i) “ordinary acids” as special (Z = 0) (ii) surface complexation. Examples are presented 1 to 6. high-N perspecti...

The acidity constants of some synthesized protonated pyrazolo quinazoline compounds were determined potentiometrically at ionic strength of 0.1 M in DMF: water (60:40 v/v) system at different temperatures (298.15 K to 318.15 K). The pKa values have been found to increase with increasing electron-donating nature of substitutions. Some thermodynamics parameters such as enthalpy (ΔH°), Gibb’s free...

Acid dissociation equilibrium constants and rate constants for disulfide interchange reactions have been measured in 50% methanol at low ionic strength for peptides containing cysteines with local ionic neighboring groups. These physical constants may be correlated by separation of free energy contributions into solvent-independent and solvent-dependent factors. The former represent inductive e...