The acid-base chemistry of a tetraprotic, ampholyte ACE inhibitor, lisinopril, was studied by different methods. Potentiometry in aqueous medium and a co-solvent technique in methanol-water mixtures as well as 1 H NMR-pH titration were applied for the highly precise measurement of protonation macroconstants. The log K values of lisinopril (at 25.0°C and 0.15 M ionic strength) were found: log K1...

Metal-free hydrogenation of imines by phosphonium borate zwitterion R2PH(CQF4)BH(C6F5)2 (1, R = CH3, tBu), has been studied by density functional theory (DFT) calculations. The study elucidates a two-step mechanism in which protonation of an imine by the phosphonium part of 1 is followed by hydride transfer to the C center from the borohydride part of 1. According to our calculations, the hydri...

We present a new computational approach for constant pH simulations in explicit solvent based on the combination of the enveloping distribution sampling (EDS) and Hamiltonian replica exchange (HREX) methods. Unlike constant pH methods based on variable and continuous charge models, our method is based on discrete protonation states. EDS generates a hybrid Hamiltonian of different protonation st...

The acid dissociation constants of long-chain esters of carnitine (5-hydroxy-~,trimethylammonium-butyrate) above the critical micelle concentration were determined potentiometrieally at several concentrations of added KC1. As the degree of protonation 5 increases the apparent pK values decrease owing to the increased positive charge on the micelle. The difference in pK between the neutral (zwit...

Complexes with bulky hydrotris(triazolyl)borate (Ttz) ligands, TtzCuCO, were used to probe how acids change the donor properties of Ttz ligands. (Ttz(tBu,Me))CuCO shows four distinct protonation states and a gradual increase in the CO stretch. The increased electrophilic nature of the Cu center upon protonation leads to enhanced C-H activation catalysis.

The review is mainly concerned with the protonation equilibria of biologically active ligands like amino acids, peptides, DNA constituents, and amino acid esters in nonaqueous media. Equilibrium concentrations of proton-ligand formation as a function of pH were investigated. Also, thermodynamics associated with protonation equilibria were also discussed.

Localized protonation of 4-mercaptopyridine (4-MPY), activated by light in the presence of silver nanoparticles is monitored under ambient conditions using surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS). The reaction can be controlled by the excitation wavelength and the atmospheric conditions, thus, providing a tool for site-specific control of protonation.

The acid-base equilibria of glycine have been studied in different aqueous solutions of 1,4-dioxane(0-50 % by v/v) using potentiometric method. In this study, the macro and micro protonationconstants of the amino acid and its tautomeric constant have been determined at 25 °C and constantionic strength 0.1 mol dm-3 (NaCl). The protonation and the tautomeric constants of glycine indifferent binar...

Protein-side-chain protonation, coupled to conformational rearrangements, is one way of regulating physiological function caused by changes in protein environment. Specifically, protonation of histidine residues has been implicated in pH-dependent conformational switching in several systems, including the diphtheria toxin translocation (T) domain, which is responsible for the toxin's cellular e...