Esin B. Sözer
Research Assistant Professor
Old Dominion University
Frank Reidy Research Center for Bioelectrics
Laboratory of Multiscale Bioelectrical Interactions
I acquired my Ph.D. in Electrical Engineering-Electrophysics at the University of Southern California (USC), Los Angeles, CA; my M.S. in Electrical Engineering from Auburn University, Auburn, AL; and my B.S. in Electronics Engineering from Hacettepe University in Ankara, Turkey. I spent two years (2012-2013) at the University of California Los Angeles (UCLA) as a postdoctoral researcher in Physics and Astronomy Department working on accelerator physics.
Below is a summary in NIH biosketch format of my scientific activities since I started my Ph.D..
1. Plasma physics applications for high power electrical switches and experimental dielectric laser accelerator physics. High power plasma switches that can handle very high currents (kiloamperes) were first developed in the 1940s for radar systems. Recent developments in semiconductor technology have made the use of these switches less common, however, could not replace them completely due to important applications that require high current handling in the kiloampere ranges such as in the powering of RF particle accelerators. My Ph.D. advisors and I aimed to develop a high voltage, high current, compact plasma switch with the capacity of traditional switches, but much smaller in size. I worked on the investigation of metal photocathodes as an electron source for a plasma switch called back-lighted thyratron. This completely new utilization of metal photocathodes was funded by an Air Force Office of Scientific Research Young Investigator Award to Dr. Chunqi Jiang. My experience as the main and sole experimentalist in this project, building experimental high vacuum setups, executing experiments, doing data analysis and preparing manuscripts, lead to my acquiring a post-doctoral position at UCLA in accelerator physics. Laser accelerators have been proposed to overcome the astronomical size and cost of traditional RF accelerators such as the monumental LHC at CERN. Dielectric laser accelerators (DLAs) were first proposed in 2001 but not experimentally demonstrated until 2013. During my postdoctoral stay at UCLA (2012-2013), we aimed to develop, build, and successfully test a DLA. During this time, I worked closely with the Stanford team who eventually lead the first successful experimental testing of a DLA. With my contribution in developing data analysis software for the huge amount of data that a typical experimental run generates, I was a part of this first successful experimental demonstration of acceleration of relativistic electrons with a DLA, whose results were published in the journal Nature.
a. Jiang C, Lane J, Song S, Pendelton S, Wu Y, Sozer E, Kuthi A, Gundersen M. Single-electrode He microplasma jets driven by nanosecond voltage pulses. Journal of Applied Physics. 2016 February 28; 119(8):083301-.
b. Peralta EA, Soong K, England RJ, Colby ER, Wu Z, Montazeri B, McGuinness C, McNeur J, Leedle KJ, Walz D, Sozer EB, Cowan B, Schwartz B, Travish G, Byer RL. Demonstration of electron acceleration in a laser-driven dielectric microstructure. Nature. 2013 Nov 7;503(7474):91-4. PubMed PMID: 24077116.
c. Sozer E, Gundersen M, Jiang C. Magnesium-Based Photocathodes for Back-Lighted Thyratrons. IEEE Transactions on Plasma Science. 2012 June; 40(6):1753-1758.
d. Sozer E, Jiang C, Gundersen M, Umstattd R. Quantum Efficiency Measurements of Photocathode Candidates for Back-Lighted Thyratrons. IEEE Transactions on Dielectrics and Electrical Insulation. 2009; 16(4):993-998.
2. Imaging tools for measuring quantitative molecular transport across cellular membranes after very short (<10 ns) pulses. The traditional explanation of small molecule transport across biological membranes after electropermeabilization is based on a single physical mechanism: passive diffusion through fixed-size cylindrical lipidic pores. These cylindrical pores are theorized to be formed due to the lowered energy barrier for reorganization of the lipid bilayer by the induced membrane potential during the pulse exposure. We did experiments that can measure the size of these pores after 5 ns exposures by using swelling of cells in isosmotic solutions of different compositions to determine average size of a permeabilization structure formed on the membrane. Typical experimental methods used in determining membrane integrity are based on only a few fluorescent molecules and reported in arbitrary fluorescence units dependent on imaging parameters, and as a result, are not easily comparable from one report to the other. I used and developed confocal microscopy methods to detect patterns of permeabilization in absolute concentration units for multiple molecules and showed that the diffusive movement of molecules is not sufficient to explain the different molecular transport patterns after electropermeabilization. I was responsible for building the experimental setups, collecting data, developing image analysis tools, and preparing manuscripts in these projects.
a. Sözer EB, Pocetti CF, Vernier PT. Asymmetric Patterns of Small Molecule Transport After Nanosecond and Microsecond Electropermeabilization. J Membr Biol. 2018 Apr;251(2):197-210. PubMed PMID: 28484798; PubMed Central PMCID: PMC5910485.
b. Sözer EB, Wu YH, Romeo S, Vernier PT. Nanometer-Scale Permeabilization and Osmotic Swelling Induced by 5-ns Pulsed Electric Fields. J Membr Biol. 2017 Feb;250(1):21-30. PubMed PMID: 27435216.
c. Sözer E, Vernier P. Handbook of Electroporation. Miklavcic D, editor. Cham: Springer International Publishing; 2017. Chapter 115-2, Measurement of Molecular Transport After Electropermeabilization. 1-18p.
d. Sözer EB, Vernier PT. Modulation of biological responses to 2 ns electrical stimuli by field reversal. Biochim Biophys Acta Biomembr. 2019 Apr 11;1861(6):1228-1239. PubMed PMID: 30981731.
3. Understanding molecular transport caused by minimal perturbations: combining quantitative experiments with molecular and analytical models. After establishing our quantitative methods with confocal microscopy, I also performed experiments with a single fluorescent dye, YO-PRO-1, after exposure to a single 6 ns pulse and showed that the transport of this molecule can continue for longer than 10 minutes. We compared the results to molecular dynamics simulations of the same dye and showed that the dye’s affinity to the membrane, neglected in theoretical models, is likely to play an important role in these transport dynamics. With the help of a graduate student, I also measured molecular transport of both anionic and cationic molecules in the same experimental system with absolute units for the first time. Through analytical models of transport, I discovered an effect of low, but non-zero, membrane potential after permeabilization. This role of membrane potential has been largely neglected in models of electropermeabilization since the theory suggests a highly conductive membrane cannot carry any potential. Our results contradicted this long-held notion repeated many times in the literature. I presented these results at BioEM 2016, where I received the first Arthur Pilla Young Scientist award. More recently my work with 2 ns permeabilization of the cell membrane with unipolar and bipolar pulses, connecting experiments to analytical modeling led to the discovery that different nonzero membrane potentials post-exposure can also directly affect cell volume regulation. I was responsible for executing the experiments together with the training and supervision of a graduate student, image analysis, analytical modeling, and preparing manuscripts in these projects. (https://arthurpilla.com/2017/03/14/meet-the-very-first-arthur-pilla-young-scientist-award-recipient/)
a. Sözer EB, Vernier PT. Modulation of biological responses to 2 ns electrical stimuli by field reversal. Biochim Biophys Acta Biomembr. 2019 Apr 11;1861(6):1228-1239. PubMed PMID: 30981731.
b. Sözer EB, Pocetti CF, Vernier PT. Transport of charged small molecules after electropermeabilization - drift and diffusion. BMC Biophys. 2018;11:4. PubMed PMID: 29581879; PubMed Central PMCID: PMC5861730.
c. Sözer EB, Levine ZA, Vernier PT. Quantitative Limits on Small Molecule Transport via the Electropermeome - Measuring and Modeling Single Nanosecond Perturbations. Sci Rep. 2017 Mar 3;7(1):57. PubMed PMID: 28246401; PubMed Central PMCID: PMC5428338.
d. Sözer EB, Haldar S, Blank PS, Castellani F, Vernier PT, Zimmerberg J. Ultra-fast electroporation of giant unilamellar vesicles — Experimental validation of a molecular model. bioRxiv [Internet]. 2020 Jan 1;2020.01.01.890137. Available from: bioRxiv 2020.01.01.890137; doi: https://doi.org/10.1101/2020.01.01.890137