PubMed · 5552511
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D G Salton. 1971. Solid state thermoluminescent dosimetry.. https://pubmed.ncbi.nlm.nih.gov/5552511/
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Direct reversible electron transfer for photosynthetic reaction center from wild type Rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film was observed in this work. The redox potential E0' = 0.46 V vs. NHE for first primary donor redox couple P/P+ was accurately measured from reversible CV or SWV peaks, which were quite close to those obtained from optic redox titration method. Reaction center (RC) in film was found re-constituted in such an ordered way that the orientation of RC favored the electron transfer in film. Thus, the protein electroactivity seems to be turned on in this artificial biomimic thin film. Furthermore, RC in the film features a photo-induced redox-peak fluctuation, suggesting an intact and functional state for RC in such film. Redox peaks were also found dependent of pH, implying a proton-coupled electron transfer occurring in film. Charge recombination was observed accompanied with change of electrochemical driving force. Electrochemical model assuming several classes of electroactive sites in the films on the electrode with a dispersion of standard potentials successfully fits SWV experimental data at different pulse height and frequency.
Background-subtraction techniques were applied to the voltammetry of nicotinamide adenine dinucleotide (NADH) at protein-modified carbon-fiber microelectrodes. The background currents at carbon-fiber electrodes were stable and voltammetric scans immediately before or after the analyte were effectively used for background subtraction. Digital step-potential waveforms were used to excite these carbon-fiber electrodes, where the resulting voltammetric analysis assessed the optimal switching and initial potentials and the electrochemical response time was determined. The initial potential was 0.0 V and the switching potential 1.1 V (versus Ag/AgCl) and the response time was approximately 300 ms. Some sensitivity to NADH was lost and voltammetric prescans were required at protein-modified electrodes to obtain a stable baseline. Current versus time was assessed by the average current of the faradaic region from each voltammogram and by differential current; the average current minus the current from a non-faradaic potential range. Differential current assessments discriminated against artifacts caused by pH (as high as 1.0 pH unit) and ionic strength flux (100 mM). These background-subtraction techniques allowed the faradaic information to be obtained quickly and conveniently while maximizing sensitivity and maintaining selectivity.
S-nitrosothiols (RSNO), such as SNAP, GSNO, and Glc-SNAP-1 exhibited a single, totally irreversible, diffusion controlled reduction peak at potentials of -0.97 V, -0.98 V and -0.91 V, respectively, vs. Ag/AgCl (3 M NaCl) reference electrode. This corresponded to the nitric oxide (NO) release from the S-nitrosothiols. A possible mechanism is proposed for the reduction process.