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An optical approach to structure-fun...

Asamoah, Osei Kwame.

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An optical approach to structure-function relationships in voltage-gated ion channels.

Record Type:	Electronic resources : Monograph/item
Title/Author:	An optical approach to structure-function relationships in voltage-gated ion channels./
Author:	Asamoah, Osei Kwame.
Description:	155 p.
Notes:	Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5028.
Contained By:	Dissertation Abstracts International65-10B.
Subject:	Biophysics, General. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3149813
ISBN:	0496090682

An optical approach to structure-function relationships in voltage-gated ion channels.
Asamoah, Osei Kwame.

An optical approach to structure-function relationships in voltage-gated ion channels. - 155 p.

Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5028.

Thesis (Ph.D.)--University of California, Los Angeles, 2004.

Cellular excitability is mediated by a diverse collection of integral membrane proteins that facilitate ionic flux with distinctive kinetics and in a voltage-dependent manner. In all cases, the voltage-sensitive phenotype is endowed by a positively charged alpha helical structure---the fourth transmembrane segment (S4). While molecular genetics combined with electrophysiological and optical techniques have identified the voltage-sensing residues and correlated their exposure and displacement to voltage sensor movement, details regarding the electrical environment and dynamics of the S4 remain elusive.

ISBN: 0496090682Subjects--Topical Terms:

1019105
Biophysics, General.

An optical approach to structure-function relationships in voltage-gated ion channels.
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040 $a UnM $c UnM
100 1 $a Asamoah, Osei Kwame. $3 1927995
245 1 3 $a An optical approach to structure-function relationships in voltage-gated ion channels.
300 $a 155 p.
500 $a Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5028.
500 $a Chair: Francisco Bezanilla.
502 $a Thesis (Ph.D.)--University of California, Los Angeles, 2004.
520 $a Cellular excitability is mediated by a diverse collection of integral membrane proteins that facilitate ionic flux with distinctive kinetics and in a voltage-dependent manner. In all cases, the voltage-sensitive phenotype is endowed by a positively charged alpha helical structure---the fourth transmembrane segment (S4). While molecular genetics combined with electrophysiological and optical techniques have identified the voltage-sensing residues and correlated their exposure and displacement to voltage sensor movement, details regarding the electrical environment and dynamics of the S4 remain elusive.
520 $a Here, I describe a novel optical technique to construct an electrostatic field profile in the Shaker K channel. A thiol-reactive electrochromic probe was covalently linked to different regions of the protein. By quantifying the voltage-dependence of a fast fluorescence signal, a direct measure of the local potential gradient was obtained. This method reveals that an electric field gradient exists near the fourth transmembrane segment with the greatest field strength in the vicinity of the second gating charge. Moreover, changes in extracellular calcium and hydrogen ion concentration modulates the electric field detected by the S4.
520 $a The dielectric environment and extent of S4 movement during Shaker K activation was also studied using spectroscopy. We employed emission spectra measurements in conjunction with quencher accessibility to show that the voltage sensor migrates into a more polar environment as it activates but does not shift between the lipid and aqueous phase. In addition, we show using FRET that the S4 does not migrate across the entire bilayer width as it moves from the closed to open state.
520 $a Cooperative interactions between individual S4 segments in the voltage-gated sodium channel was also investigated using site-specific fluorescence. By utilizing a probe that reports changes in the local environment, we evaluated the steady state fluorescence-voltage relationships of a particular S4 in the presence and absence of a distal [domain] gating perturbation. We found that all four voltage sensors in the sodium channel are coupled to varying extent with the largest apparent interaction between domain I and domain IV.
590 $a School code: 0031.
650 4 $a Biophysics, General. $3 1019105
690 $a 0786
710 2 0 $a University of California, Los Angeles. $3 626622
773 0 $t Dissertation Abstracts International $g 65-10B.
790 1 0 $a Bezanilla, Francisco, $e advisor
790 $a 0031
791 $a Ph.D.
792 $a 2004
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3149813