Species-Specific, pH-Independent, Standard Redox Potential of Selenocysteine and Selenocysteamine

Abstract

Microscopic redox equilibrium constants and standard redox potential values were determined to quantify selenolate-diselenide equilibria of biological significance. The highly composite, codependent acid-base and redox equilibria of selenolates could so far be converted into pH-dependent, apparent parameters (equilibrium constants, redox potentials) only. In this work, the selenolate-diselenide redox equilibria of selenocysteamine and selenocysteine against dithiothreitol were analyzed by quantitative nuclear magnetic resonance (NMR) methods to characterize the interfering acid-base and redox equilibria. The directly obtained, pH-dependent, conditional redox equilibrium constants were then decomposed by our method into pH-independent, microscopic constants, which characterize the two-electron redox transitions of selenocysteamine and selenocysteine. The 12 different, species-specific parameter values show close correlation with the respective selenolate basicities, providing a tool to estimate otherwise inaccessible site-specific selenolate-diselenide redox potentials of related moieties in large peptides and proteins.

Steric-free bioorthogonal profiling of cellular acetylation and glycosylation via a fluorine-selenol displacement reaction (FSeDR)

“…The selenol probe is also readily to form dimer under exposure to air which will block the reactive selenium anion warhead. 35 To reduce the dimer, we explored tris(2-carboxyethyl) phosphine (TCEP), dithiothreitol (DTT), NaCNBH 3 , or NaBH 4 to break diselenide bonds (Figure S1D-S1H). Although being odorless, more powerful and resistant to oxidation in air, TCEP was unfortunately found to react with selenol in a short time (less than 30 min).…”

“…The selenol probe is also readily to form dimer under exposure to air which will block the reactive selenium anion warhead. 35 To reduce the dimer, we explored tris(2-carboxyethyl) phosphine (TCEP), dithiothreitol (DTT), NaCNBH3, or NaBH4 to break diselenide bonds (Figure S1D-S1H).…”

Properties of Selenolate-Diselenide Redox Equilibria in View of Their Thiolate-Disulfide Counterparts

“…To obtain data describing selenolate-diselenide redox equilibria comparable to those of thiolate-disulfide systems, first, the glutathione–DTT redox reaction was investigated at a microspecies level [ 49 ].…”

“… The coexisting protonation and redox microequilibria of selenocysteamine and selenocystamine; N, and Se labels denote the amino, and selenolate groups, respectively. Reproduced from [ 49 ]. …”

Fabrication and Optimization of Nafion as a Protective Membrane for TiN-Based pH Sensors

“…Solid-state potentiometric pH sensors are composed mainly of metal oxides and have several benefits over glass electrodes, such as variable shapes, the possibility of miniaturization, high selectivity [ 6 ], low manufacturing cost with high production rate, and possibility of integration of the sensor with real-time microelectronic monitoring components. Among iron oxides, RuO 2 is highly prized for its attractive properties, such as high sensitivity [ 7 ], selectivity [ 8 ], good reaction even in the presence of highly oxidizing and reducing species [ 9 ], and stable performance in various samples [ 10 ]. However, there are still problems with the RuO 2 solid-state metal oxide electrode regarding pH measurements in complex biological, environmental, and industrial media due to redox interference.…”