Designing interfaces for biological applications
How do proteins adjust to interfacial pressure changes ?
Reference: Meyers, N. L.; Larsson, M.; Olivecrona, G.; Small, D. M., A pressure-dependent model for the regulation of lipoprotein lipase by apolipoprotein C-II. Journal of Biological Chemistry 2015, 290 (29), 18029-18044.
In order to understand how Apolipoprotein C-II (apoC-II) adapts to pressure changes, the behavior of apoC-II at multiple lipid/water interfaces was characterized. Using an automatic drop tensiometer (TRACKER™ by TECLIS), the authors showed that ApoC-II adsorption to a triacylglycerol/water interface resulted in a large increase in surface pressure. ApoC-II was exchangeable at this interface and desorbed under interfacial compressions. Analysis of gradual compressions showed that apoC-II undergoes a two-step desorption. At phospholipid/triacylglycerol/water interfaces, ApoC-II had a large exclusion pressure, similar to that of apoC-I and apoC-III. However, apoC-II desorbed at retention pressures higher than those seen with the other apoCs. This suggests that it is unlikely that apoC-I and apoC-III inhibit LPL via displacement of apoC-II from the lipoprotein surface. Upon rapid compressions and re-expansions, re-adsorption of apoC-II increased the pressure with a smaller amplitude than the initial adsorption. This indicates that apoC-II removed phospholipids from the interface upon desorption.
TECLIS product: TRACKER™ automatic drop tensiometer with bulk phase exchange.
Key words: oil water interface, phospholipids.
How is the adsorption of DSPE-PEG2000-Ma at an oil/water interface affected by the presence of lipoid/solutol ?
Reference: Arnaud Béduneau, P. S., François Hindré, Anne Clavreul,; Jean-Christophe Leroux, J.-P. B., Design of targeted lipid nanocapsules by conjugation of whole antibodies and antibody Fab’ fragments. Biomaterials 2007, 28.
In this paper, the authors characterized the impact of solutol and lipoid on the doping of an oil-water interface with DSPE-PEG2000-Mal using an automatic drop tensiometer (TRACKER™ by TECLIS). Lipoïd and solutol were first dissolved in the oil and aqueous phases respectively prior to drop formation. After a first adsorption step of solutol and/or lipoid at the oil/water interface, a second molecule DSPE-PEG2000-Mal was added to the water phase in order to dope the interface already enriched with Lipoïd and solutol molecules. Surface tension measurements showed that DSPE-PEG2000-Mal can indeed be inserted in an oil water interface already containing solutol/Lipoid.
TECLIS product: TRACKER™ automatic drop tensiometer.
Key words: surface tension, interactions
What are the contributions of the oscillating frequency and the presence of vesicles on the behavior of an adsorbed phospholipid monolayer?
Reference: Nguyen, P. N., Waton, G., Vandamme, T., & Krafft, M. P. (2013). Behavior of an adsorbed phospholipid monolayer submitted to prolonged periodical surface density variations. Angewandte Chemie International Edition, 52(25), 6404-6408.
In this paper, the authors probe the behavior of DPPC, the main component of the native lung surfactant, at the air water interface in conditions close to human respiration: 37°C, oscillations with a period varying from 3 to 100s, a surface area amplitude between 5 an 20% and in the presence of vesicles. The experiments were performed with an automatic drop tensiometer (TRACKER™ by TECLIS) and consisted in generating an air bubble in an aqueous dispersion of phospholipid vesicles and submitting it to surface area oscillations while monitoring the value of surface tension. The results showed that the oscillations speed up the adsorption of DPPC, that they allow to reach much lower surface tension values and that the surface tension value remains at its minimum after the oscillation has been removed. Moreover, the oscillation period was found to have a great impact on the adsorption kinetics of DPPC . This behavior is assigned to a coupling between the periodical variation of the surface density of the phospholipid at the air/ water interface and its liquid expended/liquid condensed transition.
TECLIS product: TRACKER™ automatic drop tensiometer
Key words: interfaces, phospholipids, respiration, tensiometry.