Meditation - Road to a Calm Mind , by G. Medovoy, September 24, 1970

Article about Dr. Rhoda LeCocq, daughter of Ralph LeCocq, who would teach a class on mysticism, meditation, and world philosophies and religions.https://nwcommons.nwciowa.edu/lecocqnewspaper/1008/thumbnail.jp

Direct knock-on of desolvated ions governs strict ion selectivity in K+ channels

The seeming contradiction that K+ channels conduct K+ ions at maximal throughput rates while not permeating slightly smaller Na+ ions has perplexed scientists for decades. Although numerous models have addressed selective permeation in K+ channels, the combination of conduction efficiency and ion selectivity has not yet been linked through a unified functional model. Here, we investigate the mechanism of ion selectivity through atomistic simulations totalling more than 400 μs in length, which include over 7,000 permeation events. Together with free-energy calculations, our simulations show that both rapid permeation of K+ and ion selectivity are ultimately based on a single principle: the direct knock-on of completely desolvated ions in the channels' selectivity filter. Herein, the strong interactions between multiple 'naked' ions in the four filter binding sites give rise to a natural exclusion of any competing ions. Our results are in excellent agreement with experimental selectivity data, measured ion interaction energies and recent two-dimensional infrared spectra of filter ion configurations

Theater of the Community

(Statement of Responsibility) by Arkady Medovoy(Thesis) Thesis (B.A.) -- New College of Florida, 1999(Supplements) Accompanying materials: Videocassette included.(Electronic Access) RESTRICTED TO NCF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE(Bibliography) Includes bibliographical references.(Source of Description) This bibliographic record is available under the Creative Commons CC0 public domain dedication. The New College of Florida, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.(Local) Faculty Sponsor: McDiarmid, Joh

Structural mechanism of voltage-dependent gating in an isolated voltage-sensing domain

The voltage-sensing domain (VSD) is a common scaffold responsible for the transduction of transmembrane electric fields into protein motion. They play an essential role in the generation and propagation of cellular signals driven by voltage gated ion channels, voltage sensitive enzymes and proton channels. All available VSD structures are thought to represent the activated conformation of the sensor due to the overall structural similarities and the mid-point of the voltage dependence of activation curves. Yet, in the absence of a resting state structure, the mechanistic details of voltage sensing remain controversial. The voltage dependence of the VSD from Ci-VSP (Ci-VSD) is dramatically right shifted, so that at 0 mV it presumably populates the putative resting state. We have determined crystal structures of the Ci-VSP voltage sensor in both active (Up) and resting (Down) conformations, between which the S4 undergoes a ∼5 Å displacement along its main axis with an accompanying 55-90o rotation resembling the basic helix-screw mechanism of gating. In the process, the gating charges change position relative to a “hydrophobic gasket” that electrically separates intra and extracellular compartments. This movement is stabilized by an exchange in countercharge partners in helices S1 and S3, for an estimated net charge movement of ∼1 eo. EPR spectroscopic measurements confirm the limited nature of S4 movement in a membrane environment. These results provide an explicit mechanism of voltage sensing in diverse voltage dependent cellular responses