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Open Access Research article

Fluorescence anisotropy of diphenylhexatriene and its cationic Trimethylamino derivative in liquid dipalmitoylphosphatidylcholine liposomes: opposing responses to isoflurane

Steven C Nelson13, Steven K Neeley14, Eric D Melonakos15, John D Bell16 and David D Busath2*

Author Affiliations

1 Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84602 USA

2 WIDB 574, Dept. of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84602, USA

3 The University of Toledo College of Medicine, 3045 Arlington Avenue, Mail Stop 1043, Toledo, OH 43614, USA

4 University of Texas Southwestern, 5323 Harry Hines Blvd., Dallas, TX 75390-9003, USA

5 Dept. of Bioengineering, Univ. of Utah, Salt Lake City, UT 84112, USA

6 Dean of Undergraduate Education, Brigham Young University, Provo, UT 84602, USA

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BMC Biophysics 2012, 5:5  doi:10.1186/2046-1682-5-5

Published: 24 March 2012

Abstract

Background

The mechanism of action of volatile general anesthetics has not yet been resolved. In order to identify the effects of isoflurane on the membrane, we measured the steady-state anisotropy of two fluorescent probes that reside at different depths. Incorporation of anesthetic was confirmed by shifting of the main phase transition temperature.

Results

In liquid crystalline dipalmitoylphosphatidylcholine liposomes, isoflurane (7-25 mM in the bath) increases trimethylammonium-diphenylhexatriene fluorescence anisotropy by ~0.02 units and decreases diphenylhexatriene anisotropy by the same amount.

Conclusions

The anisotropy data suggest that isoflurane decreases non-axial dye mobility in the headgroup region, while increasing it in the tail region. We propose that these results reflect changes in the lateral pressure profile of the membrane.