The influence of simple salts on the ion exchange and protonation equilibria of an amphoteric ion-exchange resin, which has strong base and weak acid moieties in a single functional group fixed onto the styrene-DVB matrix, has been investigated. Concentrations of ionic species in the amphoteric ion-exchange resin in equilibrium with various sodium salt solutions were estimated by (23)Na NMR spe...

The structure and function of macromolecules depend critically on the ionization (protonation) states of their acidic and basic groups. A number of existing practical methods predict protonation equilibrium pK constants of macromolecules based upon their atomic resolution Protein Data Bank (PDB) structures; the calculations are often performed within the framework of the continuum electrostatic...

Stopped-flow fluorometry was used to study the kinetics of the reactive center loop insertion occurring during the reaction of N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-3-diazole (NBD) P9 plasminogen activator inhibitor-1 (PAI-1) with tissue-(tPA) and urokinase (uPA)-type plasminogen activators and human pancreatic elastase at pH 5.5-8.5. The limiting rate constants of reactive...

Chemical shifts of fully bound substrates of the arginine kinase reaction were measured in 31P NMR spectra of various binary, ternary, quaternary, and transition state analog complexes. Three of the four substrates of the reaction, namely ATP, ADP, and phosphoarginine contain a total of six phosphate groups and each one can be readily distinguished in the s1P NMR spectra. Binding to the enzyme ...

An E-4-styrylpyridine derivative endowed with 18-crown-6 as a substituent (E-1) was prepared and evaluated in acetonitrile as a potential ditopic ligand for protonated amino acids. The interactions of E-1 with the protonated amino acid perchlorates, ClO(4)(-) H(3)N(+)(CH(2))(n)COOH (n = 2, 5 and 10, A2, A5 and A10, respectively), were studied by optical methods, (1)H NMR and mass spectroscopy. ...