Mechanics of lipid bilayer junctions affecting the size of a connecting lipid nanotube.
Bottom Line:
An electrochemical method monitoring diffusion of electroactive molecules through the nanotube has been used to determine the radius of the nanotube R as a function of nanotube length L for the two configurations.The data show that the LNT connected in the TVC constricts to a smaller radius in comparison to the tube-only mode and that tube radius shrinks at shorter tube lengths.In particular, this model allows us to estimate the surface tension coefficients from R(L) measurements.
Affiliation: BioNano Systems Laboratory, Institute for Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg, Sweden. marina.voinova@chalmers.se.
ABSTRACT
In this study we report a physical analysis of the membrane mechanics affecting the size of the highly curved region of a lipid nanotube (LNT) that is either connected between a lipid bilayer vesicle and the tip of a glass microinjection pipette (tube-only) or between a lipid bilayer vesicle and a vesicle that is attached to the tip of a glass microinjection pipette (two-vesicle). For the tube-only configuration (TOC), a micropipette is used to pull a LNT into the interior of a surface-immobilized vesicle, where the length of the tube L is determined by the distance of the micropipette to the vesicle wall. For the two-vesicle configuration (TVC), a small vesicle is inflated at the tip of the micropipette tip and the length of the tube L is in this case determined by the distance between the two interconnected vesicles. An electrochemical method monitoring diffusion of electroactive molecules through the nanotube has been used to determine the radius of the nanotube R as a function of nanotube length L for the two configurations. The data show that the LNT connected in the TVC constricts to a smaller radius in comparison to the tube-only mode and that tube radius shrinks at shorter tube lengths. To explain these electrochemical data, we developed a theoretical model taking into account the free energy of the membrane regions of the vesicles, the LNT and the high curvature junctions. In particular, this model allows us to estimate the surface tension coefficients from R(L) measurements. No MeSH data available. Related in: MedlinePlus |
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Mentions: When fitting the curve (7) to the dataset for the TVC, the parameter values are r ≈ 1.7 nm and σ/k ≈ 89 μm-2. The corresponding values for the dataset in the case of TOC are r ≈ 1.2 nm and σ/k ≈ 54 μm-2. The relation L(R) with fitted parameters are plotted on Figure 3 (blue curves) together with measured experimental data. As expected, the parameter r is much smaller than the radius R: r/R <0.06. Therefore, the simplified form (8) and its inverse (9) can be used for the given range of values of R. Fitting the relation (9) to the measurements by minimizing (11) yields σ/k ≈ 98 μm-2, r ≈ 1.9 nm and σ/k ≈ 72 μm-2, r ≈ 1.7 nm for TVC and TOC, respectively. The corresponding curves are plotted in Figure 3 in red. The model exhibits good agreement with the empirical data. A rather large scattering of measurement points at high R values in the TOC case is reflected as about 20% difference in parameter values when using different approaches to find the best fit. In this case, the values obtained through fitting (9), namely σ/k ≈ 72 μm-2, r ≈ 1.7 nm have higher reliability. |
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Affiliation: BioNano Systems Laboratory, Institute for Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg, Sweden. marina.voinova@chalmers.se.
No MeSH data available.