EQCM characterization of self-assembled kinetics of 4-pyridyl hydroquinone at Pt surface and its ion transfer in electrochemical redox

The adsorbed kinetics, proton transportation in electrochemical redox process of 4-pyridyl hydroquinone (4PHQ) self-assembled monolayer (SAM) modified Pt electrode were studied by electrochemical quartz crystal microbalance (EQCM) in situ. It proved that the electrode was modified by a monolayer and underwent a rapid electron transfer. It was a slow adsorbed kinetic process. The ion transfer in the electrochemical redox at the SAM-modified electrode surface mainly involved into the hydrate hydrogen ion.

Ultrasonic relaxation kinetics on fast deuteron transfer reaction

Propylamine has been selected to investigate the isotope effect of a fast deuteron transfer reaction by ultrasonic relaxation method. Ultrasonic absorption coefficients of propylamine in heavy water (D2O) at 25 degrees C in the concentration range from 0.0107 to 0.6300 mol dm(-3) have been measured by pulse and resonance methods over the frequency range from 0.8 to 220 MHz. A Debye-type single relaxation absorption has been observed in the solution. From the dependence of the ultrasonic relaxation parameters on the concentration and solution pH, the source of the observed relaxation has been attributed to a perturbation of the chemical equilibrium associated with the deuteron transfer reaction. The rate and equilibrium constants have been determined by the measurement of the deuteroxyl ion concentration dependence of the relaxation frequency. Also the standard volume change of the reaction has been determined from the concentration dependence of the maximum absorption per wavelength and the adiabatic compressibility has been calculated from the density and the sound velocity in the solution. These results have then been compared with those obtained for propylamine in light water (H2O). The forward rate constant is greater and the reverse rate constant is smaller in DO than in H2O. The standard volume change for deuteron transfer is greater than that for proton transfer reaction, and the adiabatic compressibility shows a similar trend. These data support an argument that there exists a stronger hydrogen bond in D2O than in H2O. The difference of the stability in the intermediate states, R-ND3+... OD- and R-NH3+... OH-, has also been considered from the results of the isotope effects.

Effect of lanthanum ions on tRNA(Phe) structure: Imino proton NMR spectroscopy

The effect of lanthanum ions on the structural and conformational change of yeast tRNA(Phe) was studied by H-1 NMR. The results suggest that the tertiary base pair (G-15)(C-48), which was located in the terminal in the augmented dihydrouridine helix (D-helix), was markedly affected by adding La3+ and shifted 0.33 downfield. Based pair (U-8)(A-14), which is associated with a tertiary interaction, links the base of the acceptor stem to the D-stem and anchors the elbow of the L structure, shifted 0.20 upfield. Another imino proton that may be affected by La3+ in tRNA(Phe) is the tertiary base pair (G-19)(C-56). The assignment of this resonance is tentative since it is located in the region of highly overlapping resonances between 12.6 and 12.2. This base pair helps to anchor the D-loop to the T psi C loop.