## 2 Materials and Methods
### Charge Measurements  
Schematic representation of the experimental setup, used to measure the amount of charge in the measuring cell, is shown in Figure 1.  
The charge measurements were carried out with a highly sensitive electrometer connected to a flow-based sample injection system for atomic force microscopy (AFM)-based fishing. The flow-based system was based on polymeric communications [32] (see Figure 1). The main elements of the sample supply system were: a peristaltic pump; a pipe with a tip for water supply; and a measuring cell. In the course of measurements, water was continuously pumped from a 50-mL polypropylene reservoir (1) into the cell (6) through the tip (5) with an Ismatech (IDEX) peristaltic pump (3). A sterile silicone pipe (4) (40 cm length, 2 mm i.d.) with a polypropylene tip (5) (a standard disposable Eppendorf-type pipette tip with a nominal capacity of 10 \(\upmu\)l and nozzle diameter \(\mathcal{O}\) = 0.4 mm) was used to supply water into the cell. The volume flow rate was varied from 0.9 to 7.2 mL/min, which corresponds to the linear velocity of the flow through the nozzle from 0.12 to 0.96 m/s. To maintain a constant level of the potential in the reservoir (1) with water, from which water was supplied into the supply pipe, a grounding electrode (Eg) was inserted into the pipe. The distance between the electrode in the pipe and the tip nozzle orifice was 15 cm. The stainless steel cell (6) served as an inner cylinder in the system, connected with the electrometer (7). In general, the measurement system was analogous to that used in [32]. The charge was registered in the cell by means of an electric system (7) based on an electrometer developed in Institute of Biomedical Chemistry (IBMC). The charge measurement accuracy was 0.1 nC. Water temperature was set and maintained constant with a thermostat, into which the reservoir was placed (1). Experiments were carried out at 38 \({}^{\circ}\)C. The duration of the preliminary equilibration of the system under the experimental conditions was no less than two hours. The duration of one measurement was seven minutes. The experimental series for each set of conditions comprised at least three repetitions.  
The experiment technique was as follows. The system was filled with water from the reservoir (1), and flushed with \(\sim\)10 mL of water. After the flush, the supplying system remained filled with water. Water was removed from the measuring cell with a pipette. Firstly, control measurements of the signal baseline for an empty cell were performed (three repetitions). Then, the pump was turned on, and water was supplied into the cell. From the moment the pump is turned on, the experiment time counting and recording the readings of the measuring system from the electrometer display started. Recording was performed with a 15-s interval during 7 min. After finishing the measurements in one experiment, the readings were reset. The so-obtained data were present in the form of time dependencies of the amount of charge entering the measuring cell \(\Delta q(t)\). The measuring cell was empty. After each measurement, the cell was emptied, and the charge was drained to prepare the next measurement in a series.