Issue 33, 2012

Poly-ethylene glycol induced super-diffusivity in lipid bilayer membranes

Abstract

Fluorescence lifetime correlation spectroscopy (FLCS) has been used to probe the influence of PEG-8000 on the fluidity of fluorescently labeled planar supported lipid bilayers on ozone plasma treated glass. The lipid membrane compositions examined were; DOPC, DOPC/DOPS (80/20 mol/mol) and DMPC, with and without cholesterol. The lateral diffusion coefficients (D) for supported lipid bilayer films of these layers without cholesterol were 7.9 ± 0.2, 7.9 ± 0.4 and 5.5 ± 0.1 μm2 s−1 respectively. The high fluidity reflected the super-hydrophilicity (contact angle of 0) of the ozone treated plasma glass substrate. Using DOPE conjugated Atto 655 as a probe, exposure of the lipid bilayer to a 30% wt/wt aqueous solution of PEG, followed by washing, dramatically increased the diffusion coefficients of the probe within the film. For example, the diffusion coefficient for the DOPC bilayer increases by nearly an order of magnitude to 51.4 ± 2.6 μm2 s−1. The autocorrelation curves for DOPC/DOPS (80/20 mol/mol) and DMPC bilayers required a two-component model for adequate fit of their behaviour yielding both fast and slow components of the diffusion. In all cases, when hydrophilic DOPE–Atto 655 was used as the probe, treatment of the lipid bilayer with PEG resulted in non-Brownian diffusion. Importantly, the observed diffusion behavior observed depends on the identity of probe. In contrast, when a hydrophobic probe (DOPE–NapthBodipy) was employed PEG showed relatively little impact on the observed diffusion rates. This was attributed to orientation of the reporter probe in the lipid bilayer and its aqueous interface. Specifically, DOPE–Atto 655 is believed to associate strongly with PEG mesh at the aqueous interface of the lipid bilayer, its diffusion strongly influenced by the structure in this region, whereas DOPE–NapthBodipy remains in the interior of the bilayer where it is relatively uninfluenced by PEG.

Graphical abstract: Poly-ethylene glycol induced super-diffusivity in lipid bilayer membranes

Supplementary files

Article information

Article type
Paper
Submitted
30 Mar 2012
Accepted
02 Jul 2012
First published
13 Jul 2012

Soft Matter, 2012,8, 8743-8751

Poly-ethylene glycol induced super-diffusivity in lipid bilayer membranes

T. Tabarin, A. Martin, R. J. Forster and T. E. Keyes, Soft Matter, 2012, 8, 8743 DOI: 10.1039/C2SM25742D

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements