Uvprobe 2

Diminazene solutions (20 μM) were prepared in 20 mM sodium phosphate buffered at pH 1–13. Spectrums were acquired with in an UV-1800 spectrophotometer (Shimadzu) with quartz cuvettes. The spectrophotometer was set to record a spectrum between wavelengths of 240–550 nm. Baseline was corrected with sodium phosphate solutions of corresponding pH. Data were analyzed with UVProbe 2.33 (Shimadzu).

Strains were either cultivated in BG11 medium which contains 17.6 mM nitrate or alternatively in BG110 medium without nitrate that was supplemented with 5 mM arginine. Notably, 10 mM glucose was added as indicated. DCMU was added at a concentration of 10 mM. For precultures, 50 ml of BG11 medium were inoculated with cells and antibiotics in the case of mutants in 100 ml Erlenmeyer flasks on a rotary at 28°C, 50 μE/m²/s, and 100 rpm. After several days of growth, cultures were pelleted and washed twice in the medium of choice without antibiotics for growth experiments. Cells were inoculated into 200 ml BG-11 at an OD750 of 0.05 and placed into glass tubes with a diameter of 3.5 cm bubbled with air at 50 μE/m²/s at 28°C, and growth was monitored every 24 h by measuring the optical density at 750 nm as described earlier (Makowka et al., 2020 (link)). The optical density (OD) of the culture was determined by photometrical analysis (UV 2501 PC Photometer, Shimadzu, Kyoto, Japan) at 750 nm, and its data were recorded and analyzed using the affiliated software UVProbe 2.33 (Shimadzu, Kyoto, Japan). Samples were diluted with BG11 medium by 1:10 when samples showed an OD₇₅₀ value above 0.5.

Sample preparation: Samples were analyzed in their original formulation.
UV equipment: A NanoDrop OneC (Thermo Fisher Scientific Inc., Waltham, MA, USA) high resolution UV–Vis spectrophotometer provided with a software capable of suppressing excipient interference was used for the analysis. M-cresol and acetate buffer UV spectra were used for the proper subtraction of the excipients’ contributions. Samples were measured as triplicates from 350 to 220 nm in intervals of 0.5 nm. One µL solution drops was directly applied to the pedestal, as recommended by the manufacturer. Second derivative spectra were calculated using the Savitzky–Golay algorithm with a five-point data filter with UVProbe 2.62 software (Shimadzu, Kyoto, Japan) application from 310 to 250 nm.