Electromagnetic and thermal characterization of an UHF-applicator for concurrent irradiation and high resolution non-perturbing optical microscopy of cells

To permit trans-illuminated, high-resolution optical microscopy during unperturbed ultrahigh frequency (UHF) irradiation, a novel new class of applicator has been designed based upon a shielded-pair transmission line. As constructed and tested with water-immersion optics and air cooling, the applicator works most robustly over 700-1100 MHz and permits SARs at the cell layer as high as 50 W/kg before the steady state temperature rise at the cell-layer exceeds 0.5 K.     

An optical and non‐invasive method to detect the accumulation of ubiquitin chains

The accumulations of excess amounts of polyubiquitinated proteins are cytotoxic and frequently observed in pathologic tissue from patients of neurodegenerative diseases. Therefore, optical and non‐invasive methods to detect the increase of the amounts of polyubiquitinated proteins in living cells is a promising strategy to find out symptoms and environmental cause of neurodegenerative diseases, also for identifying compounds that could inhibit gathering of polyubiquitinated proteins. Therefore, we generated a pair of fluorescent protein [Az amig reen (Azg) and Ku sabirao range (Kuo)] tagged ubiquitin on its N‐terminus (Azg‐Ub and Kuo‐Ub) and developed an Azg/Kuo‐based F luorescence R esonance E nergy T ransfer (FRET) assay to estimate the amount of polyubiquitin chains in vitro and in vivo. The FRET intensity was attenuated in the presence of ubiquitin‐activating enzyme inhibitor, PYR‐41, indicating that both fluorescent ubiquitin is incorporated into ubiquitin chains likewise normal ubiquitin. The FRET intensity was enhanced by the addition of the proteasome inhibitor, MG‐132, and was reduced in the presence of the autophagy activator Rapamycin, designating that ubiquitin chains with fluorescent ubiquitin act as the degradation signal equally with normal ubiquitin chains. In summary, the above optical methods provide powerful research tools to estimate the amounts of polyubiquitin chains in vitro and in vivo, especially non‐invasively in living cells.     

A multi‐resolution model to capture both global fluctuations of an enzyme and molecular recognition in the ligand‐binding site

In multi‐resolution simulations, different system components are simultaneously modeled at different levels of resolution, these being smoothly coupled together. In the case of enzyme systems, computationally expensive atomistic detail is needed in the active site to capture the chemistry of ligand binding. Global properties of the rest of the protein also play an essential role, determining the structure and fluctuations of the binding site; however, these can be modeled on a coarser level. Similarly, in the most computationally efficient scheme only the solvent hydrating the active site requires atomistic detail. We present a methodology to couple atomistic and coarse‐grained protein models, while solvating the atomistic part of the protein in atomistic water. This allows a free choice of which protein and solvent degrees of freedom to include atomistically. This multi‐resolution methodology can successfully model stable ligand binding, and we further confirm its validity by exploring the reproduction of system properties relevant to enzymatic function. In addition to a computational speedup, such an approach can allow the identification of the essential degrees of freedom playing a role in a given process, potentially yielding new insights into biomolecular function. Proteins 2016; 84:1902–1913. © 2016 Wiley Periodicals, Inc.     

Design,implementation, and dosimetry analysis of an S‐band waveguide in vitro system for the exposure of cell culture samples to pulsed fields

The interaction between electromagnetic fields and biological media, particularly regarding very high power, short pulses as in radar signals, is not a fully understood phenomenon. In the past few years, many in vitro, cellular communications‐oriented exposure studies have been carried out. This article presents a high‐power waveguide exposure system capable of dealing with monochromatic, multicarrier or pulsed signals between 1.8 and 3.2 GHz (L‐ and S‐band) with a pulse duration as low as 90 ns, minimum pulse repetition of 100 Hz, and maximum instantaneous power of 100 W. The setup is currently being used with a 2.2 GHz carrier modulated by 5 µs pulses with a 100 Hz repetition period and approximately 30 W of instantaneous power. After a worst‐case temperature analysis, which does not account for conduction and convection thermal effects, the experiment's exposure is considered sub‐thermal. Evaluation of the results through the specific absorption rate distribution is not considered sufficient enough in these cases. An electromagnetic field distribution analysis is needed. For monochromatic signals, the representation of the modulus of the electric and magnetic field components is proposed as a suitable method of assessment. Bioelectromagnetics 31:479–487, 2010. © 2010 Wiley‐Liss, Inc.