H. Richard Leuchtag is the recipient of a National Academy of Sciences travel grant to Kyoto, Japan, in 1978 and a University of Texas Intramural grant in 1982.
KERRVILLE, TX, October 23, 2018 /24-7PressRelease/ -- Marquis Who's Who, the world's premier publisher of biographical profiles, is proud to present H. Richard Leuchtag, Ph.D., with the Albert Nelson Marquis Lifetime Achievement Award. An accomplished listee, Dr. Leuchtag celebrates many years' experience in his professional network, and has been noted for achievements, leadership qualities, and the credentials and successes he has accrued in his field. As in all Marquis Who's Who biographical volumes, individuals profiled are selected on the basis of current reference value. Factors such as position, noteworthy accomplishments, visibility, and prominence in a field are all taken into account during the selection process.
A retired biophysics researcher and biology educator, Dr. Leuchtag taught at Texas Southern University, beginning in 1982 as an assistant professor and concluding his career in 1997 as a professor. A former researcher at the University of Texas Medical Branch and instructor at Indiana University-Purdue University Indianapolis, Dr. Leuchtag also served as an associate editor for "Physics Today" in New York City and as a research associate in the biophysics research laboratory at New York University (NYU).
In his work on the biophysical problem of ion conduction across excitable membranes, Leuchtag rejected approaches based on questionable assumptions. With James Swihart, he focused on classical electrodiffusion theory based on electrodynamics and the Nernst–Planck equation. He developed a family of ordinary differential equations for stationary multi-ion electrodiffusion systems and found approximate solutions for time-varying ion currents across membranes. With Harvey M. Fishman and L. E. Moore, he measured spectral admittance and fluctuations of squid-axon membrane, demonstrating that the membrane–ion system is nonlinear.
The exact solutions Leuchtag computed for the two-ion stationary case of classical electrodiffusion proved inadequate to explain experimental data. Suspecting that this was due to the assumption of a constant parameter to characterize the electrical properties of the membrane–ion system, he replaced the constant with an equation that makes the dielectric coefficient, epsilon, a function of the electric field. Leuchtag borrowed this equation from the theory of ferroelectrics. These materials, which possess a switchable polar structure, exhibit similarities to excitable membranes, including critical temperatures, hysteresis and surface charges. Leuchtag's quantitative fit of the temperature variation of membrane capacitance with the Curie–Weiss law of ferroelectrics helps support his hypothesis of the field dependence of epsilon.
When structural studies of the voltage-sensitive ion channels responsible for membrane excitability revealed that these molecules possess positively charged amino acids in their voltage-sensing domains, Leuchtag realized that these like charges must repel one another. The electrostatic repulsions in S4 segments must depend on the channel's epsilon. In the model of channel activation by bioferroelectricity that Leuchtag developed with Vladimir S. Bystrov, epsilon depends on the voltage across the membrane.
Since epsilon is a spatial average of electric dipole moments, the question arose, "Where in the ion channel are these dipoles located?" Data on ferroelectric liquid crystals containing branched-chain amino acids, aromatics and chiral centers, like those in voltage-sensitive ion channels, provides an answer, as these materials exhibit large and variable dielectric coefficients. Leuchtag reasoned that the branched tails of these numerous amino acid groups would diverge and sprout induced dipole moments when the membrane is under the resting electric field of about ten million volts per meter, making epsilon large. When an approaching impulse discharges this field to a value below threshold, the branched chains will collapse and lose their induced dipole moments. Epsilon would thus drop on depolarization and, as Leuchtag calculated from Coulomb's law, cause repulsion energies to greatly increase. These repulsions must expand the S4 segments, consistent with reports of their outward motions.
Leuchtag hypothesized that expansion of the voltage sensors drives a shape change in the ion channel as a whole, creating ion vacancies in the pore domain that enable selective ion percolation. By accounting for the observed stochastic ion currents, this model explains gating at the molecular level. With Hervé Duclohier and others, Leuchtag found that replacement of branched residues with unbranched ones changes the membrane currents, confirming their role in voltage sensing and activation. Leuchtag's 2008 book, Voltage-Sensitive Ion Channels: Biophysics of Molecular Excitability, summarizes progress in this field.
A former consultant in the biophysics department at NYU during 1978 and summer investigator in the Marine Biological Laboratory in Woods Hole, MA, during much of the 1980s, Dr. Leuchtag has long been a member of the American Physical Society, the Biophysical Society, The Scientific Research Society—Sigma Xi, and ResearchGate. Locally involved, he has served as a member of the Progressive Book Club in Kerrville, TX, and is a member, treasurer and newsletter editor for the Unitarian Universalist Fellowship of Kerrville.
The recipient of a National Academy of Sciences travel grant to Kyoto, Japan, in 1978, a University of Texas Intramural grant in 1982, and a five-year National Institutes of Health-RCMI grant from 1986 to 1991, Dr. Leuchtag has been included in the first edition of Who's Who in Science and Engineering and the 23rd edition of Who's Who in the South and Southwest.
Born in Breslau, Germany, Dr. Leuchtag emigrated to Panama in 1938 and settled in the United States in 1940, later acquiring a Bachelor of Arts and Master of Arts at the University of California, Los Angeles, in 1950 and 1954, respectively, followed by graduate coursework at UCLA Medical Center from 1955 to 1957. Dr. Leuchtag served in the U.S. Army between 1951 and 1953 as a corporal at Army Field Forces Board #4 in Fort Bliss, TX. He then worked as a Physicist—Acoustic Homing Specialist at the U.S. Naval Ordnance Test Station in Pasadena, California. In 1954 he took a leave of absence to obtain an advanced degree at UCLA. There he met Alice Kathleen (Kesner) Leuchtag, who would become his wife, and they decided to work together as a team. She would switch from Sociology to Experimental Psychology and he, from Physics to Biophysics. He later earned a Doctor of Philosophy at Indiana University in 1974.
Dr. Leuchtag has one son who is an attorney, as well as five grandchildren and two great-grandchildren. In his free time, he loves to cook and practice photography.
In recognition of outstanding contributions to his profession and the Marquis Who's Who community, H. Richard Leuchtag, Ph.D., has been featured on the Albert Nelson Marquis Lifetime Achievement website. Please visit www.ltachievers.com for more information about this honor.
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