Spatiotemporal Oscillations in Biological Molecules: Molybdate-L-Cysteine
Year: 2008
Type: article
Abstract: The interactions between sodium molybdate and L-cysteine at different pH values have been investigated by using cyclic voltammetry and frequency response analysis. With increasing pH values, the decreasing redox interaction was demonstrated by decreasing color, and admittance behavior, as tending towards that of L-cysteine. At pH values close to neutral and above, the two broad admittance maxima moved in opposite directions with decreasing frequencies and merged into one at around 250 Hz. This compares to the similar behavior for L-cysteine alone at pH = 5.18 and at around 10 Hz. At pH = 9.34, two pairs of maxima moving in opposite directions with decreasing frequencies and merging into two peaks were observed. The first pair was assigned to the interactions between α-NH3+ and α-COO-and the second pair to Na+ and sulfhydryl S-. The impedance exhibited negative differential resistance: impedance loci occurring in two or more quadrants at different pH values. When the potential was fine-tuned, the impedance loci extended after the first 4 quadrants again into the first and second quadrants for a total of 6 quadrants, a phenomenon observed for the first time in impedance studies. Increasing the surface area decreased the impedance but followed the same multi-quadrant impedance. When the same used Hg drop was used again for repeat measurements, the same phenomenon was observed, indicating that there was no need to have a fresh Hg drop for each experiment. A comparison of the data in the presence of sulfate instead of chloride, and the negative differential resistance observations at different pH values, suggested that heptamolybdate complexes of L-cysteine were more active. Also the presence of chloride gave smoother impedance data in the 4th and 5th quadrants at low frequencies. These data suggested that we should consider the electronic properties of these molecules as complement to enzymatic process in biological systems.
Authors: C.V. Krishnan, M. Garnett, B. Chu
Institution: Stony Brook University
Language: English
Subfield: Electrochemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,670
OpenAlex ID: W4382140995