Concentration dependence of lipopolymer self-diffusion in supported bilayer membranes
| Autor: | Huaiying Zhang, Reghan J. Hill |
|---|---|
| Rok vydání: | 2010 |
| Předmět: |
Self-diffusion
Friction Diffusion Lipid Bilayers Biomedical Engineering Biophysics Analytical chemistry Bioengineering Mole fraction Models Biological Biochemistry Polyethylene Glycols Biomaterials chemistry.chemical_compound Particle Size Lipid bilayer Research Articles Chemistry Phosphatidylethanolamines Bilayer Radius Fluoresceins Excluded volume Phosphatidylcholines Ethylene glycol Fluorescence Recovery After Photobleaching Biotechnology |
| Zdroj: | Journal of The Royal Society Interface. 8:127-143 |
| ISSN: | 1742-5662 1742-5689 |
| Popis: | Self-diffusion coefficients of poly(ethylene glycol)2k-derivatized lipids (DSPE-PEG2k-CF) in glass-supported DOPC phospholipid bilayers are ascertained from quantitative fluorescence recovery after photobleaching (FRAP). We developed a first-order reaction–diffusion model to ascertain the bleaching constant, mobile fraction and lipopolymer self-diffusion coefficientDsat concentrations in the rangec≈ 0.5–5 mol%. In contrast to control experiments with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (ammonium salt) (DOPE-NBD) in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), the lipopolymer self-diffusion coefficient decreases monotonically with increasing concentration, without a distinguishing mushroom-to-brush transition. Our data yield a correlationDs=D0/(1 +αc), whereD0≈ 3.36 µm2s−1andα≈ 0.56 (withcexpressed as a mole percent). Interpreting the dilute limit with the Scalettar–Abney–Owicki statistical mechanical theory for transmembrane proteins yields an effective disc radiusae≈ 2.41 nm. On the other hand, the Bussell–Koch–Hammer theory, which includes hydrodynamic interactions, yieldsae≈ 2.92 nm. As expected, both measures are smaller than the Flory radius of the 2 kDa poly(ethylene glycol) (PEG) chains,RF≈ 3.83 nm, and significantly larger than the nominal radius of the phospholipid heads,al≈ 0.46 nm. The diffusion coefficient at infinite dilutionD0was interpreted using the Evans–Sackmann theory, furnishing an inter-leaflet frictional drag coefficientbs≈ 1.33 × 108N s m−3. Our results suggest that lipopolymer interactions are dominated by the excluded volume of the PEG-chain segments, with frictional drag dominated by the two-dimensional bilayer hydrodynamics. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|