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Title:Improving Solution Exchange Using a Piezoeletric Micropositioning Stage to Study Ligand-Gated Ion Channels
Author(s):Saladi, Shyam
Contributor(s):Ravaioli, Umberto; Grosman, Claudio; Jakobsson, Eric
optimal inverse
piezoelectric actuator
ligand-gated ion channel
molecular evolution
Abstract:Electrophysiology constitutes one of the fundamental links between cellular biology, biophysics, and electrical engineering. Ion channels are the functional units that allow a cell to transmit and receive electrochemical stimuli, implicating them in most fundamental cellular processes. A technique known as patch clamping is used in the study of a channel’s physiology. With ligand-gate channels, the binding of a small-molecule ligand (e.g. acetylcholine for the nAChR) favors the channel transitioning into the open state. The channel activation occurs on the microsecond timescale though current measurements are limited by the solution exchange time. The state-of-the-art system applies a solution using a pizeoelectrically-controlled double lumen theta tube. Current ligand application protocols drive a piezoelectrically-controlled, double lumen theta tube via a first-order analog-filtered rectangular pulse. The resulting trajectory results in significant ringing (unwanted oscillation) in the theta tube as the pulse length is shortened. To attenuate the ringing artifacts, analog-filtering increases the rise time (exchange time of the theta tube) which again diminishes one’s ability to study the kinetics of a channel at an extreme precision. Instead, based on prior work, we use a characterized transfer function of the piezo- and theta-tube setup to generate an optimal-inverse trajectory to find the optimal output. In a second chapter, I describe and analyze, phylogenetically and structurally, a group of bacterial members of the HCN/CNG family that are more closely related to eukaryotic members than to other bacterial members – Eukaryotic-Like HCN/CNGs (ELHCN/CNGs). The ELHCN/CNGs share with the eukaryotic members a long C-linker between the permeation pathway and the cyclic-nucleotide binding domain, and features sites in the cyclic nucleotide-binding domain that are thought to give rise to cooperativity in cyclic nucleotide function. Conservation of the protein sequence coupled with major changes at the gene level suggest an important functional role for these proteins in these bacteria.
Issue Date:2014-08
Date Available in IDEALS:2014-12-19

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