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Membrane lateral mobility obstructed by polymer-tethered lipids studied at the single molecule level.
M A Deverall1, E Gindl, E-K Sinner
1Department of Chemistry, Indiana University-Purdue University Indianapolis, 402 N. Blackford St., Indianapolis, IN 46202, USA.
Biophysical Journal
|December 23, 2004
Summary
This study reveals how small obstacles impede the movement of lipids and proteins in model cell membranes. Increased obstacle concentration shifts diffusion from normal to anomalous, impacting membrane dynamics.
Area of Science:
- Biophysics
- Materials Science
- Cell Biology
Background:
- Lateral diffusion of membrane components is crucial for cellular functions.
- Understanding diffusion obstruction is key to comprehending membrane organization and dynamics.
Purpose of the Study:
- To investigate the obstructed lateral diffusion of phospholipids and proteins in a polymer-tethered lipid bilayer.
- To characterize the impact of varying concentrations of lipid-mimicking obstacles on diffusion behavior.
Main Methods:
- Wide-field single molecule fluorescence microscopy was employed to track diffusion.
- Analysis included percolation theory, free area model, and Monte Carlo lattice calculations.
- A novel procedure for identifying anomalous subdiffusion from tracking data was developed.
Main Results:
- Diffusion of both lipids (TRITC-DHPE) and proteins (bacteriorhodopsin) followed a percolating system model.
- Phospholipids and tethered lipids exhibit hard-core repulsion.
- Normal diffusion transitioned to anomalous diffusion with increasing obstacle concentration.
Conclusions:
- Tethered lipids act as randomly distributed, immobile obstacles at low to moderate concentrations.
- Small, molecular-scale obstacles significantly influence lipid and protein mobility in model membranes.
- This work enhances understanding of diffusion obstruction in biological membranes.