Hicks, Matthew R., Dafforn, Tim, Damianoglou, Angeliki, Wormell, Paul, Rodger, Alison and Hoffmann, Søren V. (2009) Synchrotron radiation linear dichroism spectroscopy of the antibiotic peptide gramicidin in lipid membranes. Analyst, Vol.134 (No.8). pp. 1623-1628. doi:10.1039/b902523e

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Abstract

We have developed synchrotron radiation linear dichroism (SRLD) to measure the insertion of peptides into lipid bilayers, significantly improving both signal-to-noise and wavelength range over existing methods. Our wavelength cut-off is currently determined by the quality of quartz in the cell, rather than the light source, with signal quality still high at the cut-off. We demonstrate the use of a lipid probe to measure the orientation of the lipid bilayers under flow and describe the way in which this can be used to further interpret SRLD data. The antibiotic peptide gramicidin is shown to exhibit drastically different kinetic and equilibrium behaviour when interacting with lipid membranes with different properties. The charge on the membrane is of interest because of differences in charge between human and bacterial membranes. For this reason we increased the negative charge on the membrane by changing the lipid composition. Increasing negative charge in the gel phase stabilises the liposomes but changes the kinetics of peptide folding. In a gel phase with no negatively charged lipids, gramicidin does not fold well and gives a small signal that indicates a change in orientation of the tryptophan side chains over time. In the fluid phase with no negatively charged lipids, there is initially > 10-fold greater peptide signal relative to the gel phase indicating a highly folded and ordered gramicidin backbone. This is followed by liposome disruption. In the gel phase with negatively charged lipids the liposomes are resistant to disruption by gramicidin and exhibit different folding kinetics depending on membrane composition. In the fluid phase with negatively charged lipids there is little signal from either the peptide or the lipid probe indicating that the liposomes have been disrupted by the gramicidin in the time it takes to make the first measurement.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QH Natural history > QH301 Biology
Divisions:	Faculty of Science > Chemistry
Library of Congress Subject Headings (LCSH):	Linear dichroism, Synchrotron radiation, Peptide antibiotics, Lipid membranes, Gramicidins
Journal or Publication Title:	Analyst
Publisher:	Royal Society of Chemistry
ISSN:	0003-2654
Official Date:	August 2009
Dates:	Date Event August 2009 Published
Volume:	Vol.134
Number:	No.8
Number of Pages:	6
Page Range:	pp. 1623-1628
DOI:	10.1039/b902523e
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC), Statens naturvidenskabelige forskningsråd (Denmark) [Danish Natural Science Research Council]

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