Experimental system for real‐time assessment of potential changes in protein conformation induced by electromagnetic fields

Abstract

A novel experimental system to distinguish between potential thermal and non-thermal effects of electromagnetic fields (EMFs) on the conformational equilibrium and folding kinetics of proteins is presented. The system comprises an exposure chamber installed within the measurement compartment of a spectropolarimeter and allows real-time observation of the circular dichroism (CD) signal of the protein during EMF exposure. An optical temperature probe monitors the temperature of the protein solution at the site of irradiation. The electromagnetic, thermal, and fluid-dynamic behavior of the system is characterized by numerical and experimental means. The number of repeated EMF on/off cycles needed for achieving a certain detection limit is determined on the basis of the experimentally assessed precision of the CD measurements. The isolated thermosensor protein GrpE of the Hsp70 chaperone system of Eschericha coli serves as the test protein. Long-term experiments show high thermal reproducibility as well as thermal stability of the experimental setup.

Off-axis electron holography of bacterial cells and magnetic nanoparticles in liquid

“…Electric and magnetic fields have been shown to play a significant role at the cellular and subcellular level, for example in plasma membranes and actin filaments [3,4], as well as in processes such as biomineralization, magnetotaxis [5,6] and magnetoreception [7]. A key example is the influence of electric fields on protein conformation, which has been described using theoretical models [8][9][10] and observed experimentally [11][12][13][14]. Charge redistribution and localization in proteins, which can be inferred using spectroscopic and computational approaches, is crucial to understanding the dynamics of protein self-assembly, aggregation and folding [3,8,[15][16][17][18].…”

Real‐time assessment of possible electromagnetic‐field‐induced changes in protein conformation and thermal stability

“…The RF EMF experimental unit (Fig. ) was described, characterized and tested previously [Beyer et al, ]. The setup supported all commonly used RF EMF irradiation protocols and allowed for pulsed exposure with user‐defined signals up to 2.5 GHz including Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) signals.…”

“…The temperature of the protein solution was continuously controlled by a FS 25 thermostat (Julabo Labortechnik, Seelbach, Germany). The whole system featured high thermal stability and repeatability within ±0.2 °C for long‐term experiments [Beyer et al, ]. The experimental unit fit into the measurement compartment of the spectropolarimeter and was connected to the electronic devices and the thermostat through light‐tight feeds.…”

“…Thus, all statistical analyses were performed with ANOVA methods. For the case of increasing temperature during RF EMF exposure, the temperature was non‐uniformly distributed within the volume of interaction due to RF EMF‐induced convection [Beyer et al, ]. The CD signal was accordingly corrected (Fig.…”

“…This study utilizes the thermal melting curve of proteins to investigate possible RF EMF‐induced effects on protein conformation. We have constructed a RF EMF exposure unit to assess in real‐time such possible concomitant effects under strictly controlled temperature conditions [Beyer et al, ]. Far‐ultraviolet (UV) circular dichroism spectroscopy (CDS) was used to observe the conformational transition of the test protein [Kelly et al, ].…”