The binding dynamics of the 2-aminoanthracenium cation (AH(+)) and 2-aminoanthracene (A) with cucurbit[7]uril (CB[7]) was studied using stopped-flow experiments. The kinetics was followed by measuring the fluorescence changes over time for AH(+) and A, which emit at different wavelengths. The studies at various pH values showed different mechanisms for the formation of the AH(+)@CB[7] complex, ...

The prototropic exchange equilibria of two drugs, nizatidine (I) and ranitidine(II), and also of structurally related the N,N'-dimethyl-2-nitro-1,1-ethenediamine molecule (III) were investigated. From the changes in electronic spectra in media of various acidity several protonation constants were determined. For pK values were -0.82, 1.95, and 6.67; for ranitidine pK values were 1.95 and 8.13; ...

The existence of protonated hydroxymethylamines of sec+ ondary amines, RzNHCHtOH, in equilibrium with hydroxymethylamines and protonated amines, has been demonstrated by titration at equilibrium and by rapid titration of the protonated hydroxymethylamines. Analogous compounds, . R3NCHeOH, are formed from formaldehyde and the sterically favorable tertiary amines: pyridine, iv-methylimidazole, an...

The pKa of a polyelectrolyte has been determined experimentally by potentiometric titration and computed using Molecular Dynamics (MD) constant pH (CpH)methodology, which allows the pKa of each titratable site along the polymer backbone to be determined separately, a procedure which is not possible by current experimental techniques. By using experimental results within the CpHMD method, the si...

The existence of protonated hydroxymethylamines of sec+ ondary amines, RzNHCHtOH, in equilibrium with hydroxymethylamines and protonated amines, has been demonstrated by titration at equilibrium and by rapid titration of the protonated hydroxymethylamines. Analogous compounds, . R3NCHeOH, are formed from formaldehyde and the sterically favorable tertiary amines: pyridine, iv-methylimidazole, an...

I. Urinary excretion of tryptophan metabolites of the kynurenine pathway before and after a loading dose of 2 g of L-tryptophan (both before and during supplementation with vitamin B6) was studied in normal young male subjects and in elderly male subjects with prostatic diseases. 2. The increase in urinary excretion of tryptophan metabolites in the normal male subjects after a loading dose of 2...

In this study, a simple infrared chemical sensor was developed for the selective detection of tryptophan in biological fluids. This sensor was capable of trapping tryptophan molecules through the formation of relatively stable metal ion complexes on the surface of the sensing element. A proline-modified sensing phase was immobilized on the surface of the internal reflection element. With the as...

Current studies provide evidence that proteins are initial targets of ROS (reactive oxygen species) in biological systems and that the damaged proteins can in turn damage other cell constituents. This study was designed to test the possibility that protein radicals generated by ROS can oxidize GSH and assess the probability of this reaction in vivo by measurement of the rate constant of this re...

The dependence on ionic strength of protonation of glycine and its complexation with dioxouranium (VI) is reported in sodium perchlorate and sodium chloride solutions as background salts. The measurements have been performed at 25±0.1°C and various ionic strengths in the range 0.1 to 1.0 mol , using a combination of potentiometric and spectrophotometric techniques. The overall analysis  of the ...