Supported Lipid Bilayers with Phosphatidylethanolamine as the Major Component

Abstract

Phosphatidylethanolamine (PE) is notoriously difficult to incorporate into model membrane systems, such as fluid supported lipid bilayers (SLBs), at high concentrations because of its intrinsic negative curvature. Using fluorescence-based techniques, we demonstrate that having fewer sites of unsaturation in the lipid tails leads to high-quality SLBs because these lipids help to minimize the curvature. Moreover, shorter saturated chains can help maintain the membranes in the fluid phase. Using these two guidelines, we find that up to 70 mol % PE can be incorporated into SLBs at room temperature and up to 90 mol % PE can be incorporated at 37 °C. Curiously, conditions under which three-dimensional tubules project outward from the planar surface as well as conditions under which domain formation occurs can be found. We have employed these model membrane systems to explore the ability of Ni to bind to PE. It was found that this transition metal ion binds 1000-fold tighter to PE than to phosphatidylcholine lipids. In the future, this platform could be exploited to monitor the binding of other transition metal ions or the binding of antimicrobial peptides. It could also be employed to explore the physical properties of PE-containing membranes, such as phase domain behavior and intermolecular hydrogen bonding.

A simple supported tubulated bilayer system for evaluating protein-mediated membrane remodeling

“…We observed tubule formation from every lipid composition tested, including zwitterionic DOPC and POPC as well as mixtures containing 25% DOPS or POPS. These lipids possess little intrinsic curvature and our SLBs are symmetric; thus, the tubule formation observed here is not likely driven by membrane asymmetry or intrinsic curvature effects as in some other systems (Sendecki et al, 2017, Kreutzberger et al, 2017). Rather, the presence of excess lipid in a confined substrate area appears to be the major driving force.…”

Formation and Characterization of Supported Lipid Bilayers Composed of Phosphatidylethanolamine and Phosphatidylglycerol by Vesicle Fusion, a Simple but Relevant Model for Bacterial Membranes

“…13−15 Recently, PE-rich SLBs were formed in mixtures with PC in an attempt to create more relevant model bacterial membranes. 9 As an alternative to vesicle fusion Langmuir–Blodgett/Langmuir–Schaefer deposition has been successfully applied to produce advanced models of bacterial membranes using PC and liposaccharides, 16−18 but this method is significantly more time-consuming and requires high technical skills to succeed. However, the membranes produced by the Langmuir–Blodgett/Langmuir–Schaefer method are asymmetric in nature and represent an accurate model of the outer membrane of Gram-negative bacteria.…”

Microtubule Binding Kinetics of Membrane-bound Kinesin Predicts High Motor Copy Numbers on Intracellular Cargo

“…Glass coverslips (#1.5, 24×30 mm, Corning) were cleaned as previously described (36). Coverslips were boiled in 7x detergent (MP Biomedicals) diluted 1:7 with 18.2 MΩ water for 2 h. Coverslips were then rinsed thoroughly with 18.2 MΩ water, blown dry with nitrogen, and annealed at 550 ℃ for 6 h. Coverslips were cleaned by a plasma cleaner (Harrick Plasma) immediately before formation of SLBs.…”

“…A 15 mW 561 nm laser (LU-N3 Laser Unit, Nikon) equipped with a Bruker Miniscanner was used to bleach Atto 647N DOPE at 50-80% output power for 3 s. The laser beam had an effectively cylindrical profile with a diameter of 30 μm. To minimize photobleaching during recovery, images were captured immediately after bleaching every 40-60 ms for 2 s, then every 500 ms for 10 s, followed by every 3 s for 2 min, and finally switched to every 30 s. Data analysis was carried out as previously described (36), using a correction factor of 1.…”