## 3 Results  
Figure 2 displays typical AFM images of the mica surface with HRP macromolecules adsorbed from the tested solutions, and corresponding cross section profiles indicated by the blue lines in the images. Figure 3 displays the density function plots of the distribution of the imaged objects with height \(\rho(h)\) and the number of visualized particles normalized per 400 \(\upmu\)m\({}^{2}\) area plotted, based on AFM data summarized for each sample. Figure 2: Results of AFM analysis for HRP solutions: typical AFM images of the mica surface with adsorbed HRP particles (left) and corresponding cross section profiles indicated by the blue lines in the AFM images (right). The measuring cell (containing HRP solution) was placed either far away at a 10 m distance from the polymeric pipe coil (control experiment) (**a**) or within the experimental setup over the coil (**b**). The scan size of each AFM image is 2 \(\upmu\)m \(\times\) 2 \(\upmu\)m, and the \(Z\) scale is 1.1 nm (**a**) and 1.2 nm (**b**). As seen from Figure 2a, in the control experiment, when the cell containing HRP solution was placed far away from the polymeric pipe coil, the protein was adsorbed onto the mica surface in the form of compact objects. The \(\rho(h)\) plot (Figure 3, black line) indicates that the height of the objects goes up from 0.8 to 2.0 nm, and the maximum number of molecules have a height of 1.0 \(\pm\) 0.2 nm. This height value is comparable with that reported in our previous papers [16, 48, 53]. Thus, it can be concluded that the objects with a height of \(\sim\)1.0 nm, observed upon AFM scanning, can be attributed to HRP monomers. The height value obtained herein for HRP monomers, adsorbed from buffered solutions, is somewhat lower than that observed in our previously reported experiments with the use of salt-free HRP solutions in ultrapure deionized water [16, 48, 53]. In the latter case, the height of monomeric HRP was determined to be \(\sim\)1.6 nm. The decrease in the height of monomeric HRP adsorbed from the buffer solution--in comparison with that obtained upon the use of salt-free HRP solutions--is supposed to be connected with an influence of the buffer on an increased screening of the interaction between the AFM probe and the substrate's surface (both of which are charged negatively). This effect can cause an increased impact of the AFM probe on the protein molecules -- upon using similar parameters of AFM scanning mode. Figure 2b displays typical AFM images obtained in working experiments when the HRP solution in the cell was placed over the coil with flowing glycerol (Figure 1). The analysis of the \(\rho(h)\) function obtained for this sample (Figure 3, left panel, red line) indicates that the height of the objects goes up from 0.8 to 2.2 nm, and the distribution maximum is 1.0 \(\pm\) 0.2 nm, which coincides with the value obtained for the control sample (Figure 3, left panel, black line). However, a significant increase in the contribution to the right wing of the distribution (i.e., an increased number of objects with heights from 1.2 to 2.0 nm) was observed. The appearance of objects with increased heights on the mica surface indicates an increase in the protein aggregation rate in the analyzed solution. These data are in agreement with those reported in our previous study on the influence of water flow on HRP in a salt-free aqueous solution. Figure 3 (right panel) shows absolute numbers of objects (\(N_{400}\)) adsorbed on the mica surface. As seen from the distribution plot in Figure 3, an increase in the number of adsorbed objects was observed for the sample incubated in the experimental setup. That is, the number of objects adsorbed on a 400 \(\upmu\)m\({}^{2}\) area amounted to 3014, while in the control experiment this number was only 676.