## 1 Introduction
[32] discussed the influence of isopropanol on enzyme-enzyme and enzyme-surface interactions on the adsorption of lipase (isolated from _Bacillus megaterium_ CCOC P2637) on polypropylene and silicon substrates. These authors have demonstrated that the addition of isopropanol to a buffered aqueous solution of the lipase promotes its disaggregation, forcing its adsorption onto hydrophilic surfaces. With the example of glutamate dehydrogenase, [PERSON] et al. [33] and [PERSON] and [PERSON] [34] demonstrated the applications of AFM for the characterization of enzyme-functionalized surfaces. Horseradish peroxidase (HRP) represents a \(\sim\)44 kDa [36] enzyme glycoprotein, whose structure is stabilized by carbohydrate chains [37; 38]. Since this enzyme is comprehensively characterized in the literature [39], many authors have used it as a model object for studying the effect of electric [40], magnetic [41; 42; 43; 44] and electromagnetic [15; 16; 17; 45; 46; 47; 48] fields on enzymes. Previously, we reported the successful use of AFM for the revelation of HRP aggregation under the influence of flow-induced electromagnetic fields [15; 16; 17]. [PERSON] et al. [43; 44] employed AFM for the investigation of the influence of alternating magnetic fields on HRP adsorption onto mica, and revealed that the action of the field on the enzyme forces it to form complex extended structures on the substrate surface. [PERSON] et al. [41] studied the effect of low-frequency rotating magnetic fields on HRP. These authors have found an increase in the enzymatic activity of HRP against o-dianisidine at 1 Hz and 20 Hz magnetic field frequencies (at which the activity increased by 8% and 12%, respectively), while the action of the field of other frequencies studied (2; 5; 10; 30; 40 and 50 Hz) were found to deactivate the enzyme. [PERSON] et al. [42] observed a very significant enhancement in the enzymatic activity of HRP against pyrogallol after its 30 min incubation in a 52 mT static magnetic field. Regarding radio frequency electromagnetic fields, [PERSON] et al. [45] have observed no nonthermal effect on HRP after the action of either a 13.56 MHz, 915 MHz or 2.45 GHz frequency. Of note, [PERSON] et al. [46] have recently reported very interesting results regarding the activation of HRP by its radio frequency (27.12 MHz) heating at 50 \({}^{\circ}\)C.  
Our present research is aimed at studying the indirect effect of glycerol flow through a cylindrical coil heat exchanger on HRP. With this purpose, we have employed the well-established approach based on AFM and spectrophotometry [15; 17; 28] for studying the effect of glycerol flow in a shielded coil on HRP. While AFM has allowed us to reveal an increase in the aggregation of HRP on the surface of mica substrates, an increase in its enzymatic activity against its substrate 2,2\({}^{\prime}\)-azino-bis(3-ethylbenzothazoline-6-sulfonate) (ABTS) in solution has also been observed. The data reported can be of interest for scientists studying the interaction of biological macromolecules with electromagnetic fields. It is to be emphasized that HRP has found numerous applications in biotechnology as a catalyst [49], and in diagnostics as a reporter enzyme [50]. Accordingly, our results can also find application in the development of water purification systems [51; 52], food treatment methods [46] and biomarker detection systems [53], considering the development of enzyme-based biosensors [53] and bioreactors with surface-immobilized enzymes [52].