Pgstat128n potentiostat

During simulated tDCS measurement, an agar block was used as a skin phantom since the electrical properties are similar to real skin. In addition, 0.9% NaCl solution can simulate the subcutaneous tissue well [40 (link)]. The agar skin phantom was prepared as follows. Firstly, 1.0 g of agar powder was added into 50 mL of heated 0.9 wt.% NaCl solution, and was stirred until the agar was completely dissolved. Then, the mixture was cooled to room temperature to form an agar block [40 (link)]. A two-electrode configuration was used for simulated tDCS experiments, consisting of two CNT/Ag/AgCl-721 electrodes as the working and counter electrodes, respectively. These two electrodes were placed on the surface of the agar skin phantom, at the center-to-center distance of 5 cm, approximately. An amount of 1.5 mL of GT10 conductive gels were injected between the electrode and agar block. The constant anodal current of 2 mA was applied to the two electrodes by an Autolab PGSTAT128N potentiostat (Metrohm Autolab BV, Utrecht, the Netherlands), and the measurements were automatically terminated when the output voltage reached 10 V.

Nanostructured silver electrodes were prepared from 3 mm diameter planar silver electrodes (Metrohm Autolab) as described previously.51 RCLH1X, RCLH1 or RC proteins at a concentration of 30 μM were drop-casted onto the prepared electrodes in the dark at 4 °C for 15 minutes and unbound protein was removed by repeated mechanically-controlled dipping in 20 mM Tris (pH 8) at 4 °C. Protein-coated electrodes were mounted in a photoelectrochemical cell fitted with a platinum counter electrode and a Ag/AgCl/3 M KCl reference electrode, and immersed in an electrolyte solution comprising 20 mM Tris (pH 8) supplemented with 200 μM cyt c and 1.0 mM ubiquinone-0 (Q₀).51 Photocurrents were measured at room temperature and a bias potential of –100 mV vs. Ag/AgCl under the control of a PGSTAT128N potentiostat (Metrohm Autolab). Illumination was supplied by an 870 nm LED (Roithner Lasertechnik) with an irradiance of 46 mW cm^–2 at the electrode surface.

The ASV experiment was performed with live cells. Cells were cultivated in copper deficient conditions (YPD + 250 μM BCS) for 24h at 30°C to remove loosely bound copper on the surface of the Cn cells. Prior to analysis, cells were harvested and washed 3x with 25 mL PBS and resuspended in PBS. Cells were counted twice and normalized to either 10⁵ cells/ mL or 10⁷ cells/mL (in PBS) for analysis. Copper concentration between 250 nM to 1000nM were titrated stepwise into 20 mL cell suspensions and copper adsorption after each titration step was measured using a static mercury drop electrode (663VA Stand and PGSTAT 128N potentiostat, Metrohm-Autolab, drop size 2), an Ag/AgCl, KCl (3 M) reference electrode with a 3M KCl salt bridge, and a glassy carbon counter electrode. Samples were initially purged with highpurity N2 (5.0, Airgas) for 180 s. ASV stripping peak currents were measured after a deposition time of 90s at -1.2 V. After an equilibration time of 5 s, the potential was ramped from −1.2V to 0V using a square wave voltammetry (scan rate 0.12Vs−1; amplitude 0.02V; frequency 60Hz). For analysis the measured curve was smoothed and the peak height at E = -0.12V was determined. For each titration experiment, the peak height was plotted against titrated Cu concentration and a linear regression was performed to calculate the slope (measured current/ nM Cu).