Ether- versus Ester-Linked Phospholipid Bilayers Containing either Linear or Branched Apolar Chains

Abstract

We studied the properties of bilayers formed by ether-and ester-containing phospholipids, whose hydrocarbon chains can be either linear or branched, using sn-1,2 dipalmitoyl, dihexadecyl, diphytanoyl, and diphytanyl phosphatidylcholines (DPPC, DHPC, DPhoPC, and DPhPC, respectively) either pure or in binary mixtures. Differential scanning calorimetry and confocal fluorescence microscopy of giant unilamellar vesicles concurred in showing that equimolar mixtures of linear and branched lipids gave rise to gel/fluid phase coexistence at room temperature. Mixtures containing DHPC evolved in time (0.5 h) from initial reticulated domains to extended solid ones when an equilibrium was achieved. The nanomechanical properties of supported planar bilayers formed by each of the four lipids studied by atomic force microscopy revealed average breakdown forces Fb decreasing in the order DHPC ≥ DPPC > DPhoPC >> DPhPC. Moreover, except for DPPC, two different Fb values were found for each lipid. Atomic force microscopy imaging of DHPC was peculiar in showing two coexisting phases of different heights, probably corresponding to an interdigitated gel phase that gradually transformed, over a period of 0.5 h, into a regular tilted gel phase. Permeability to nonelectrolytes showed that linear-chain phospholipids allowed a higher rate of solute + water diffusion than branched-chain phospholipids, yet the former supported a smaller extent of swelling of the corresponding vesicles. Ether or ester bonds appeared to have only a minor effect on permeability.

A statistical anomaly indicates symbiotic origins of eukaryotic membranes

“…It is also interesting that the appearance of oxygen (∼2 Ga) might have aided the introduction of unsaturation in the tails of membrane lipids as the presence of multiple bonds was seen in all domains only after ∼2 Ga (see Figure 4, A–C ). As a lipid's tail branching provides structural stability at high temperatures, resistance to oxidation, reduction of permeability to nonelectrolytes ( Balleza et al. , 2014 ), and promotion of tubulation/curvature formation in ether lipids ( Kozlov et al.…”

Physical properties of model biological lipid bilayers: insights from all-atom molecular dynamics simulations

“…As a result, many electrostatically driven phenomena, such as binding and permeation of charged or polar molecules, as well as dynamics and interactions of ligands and corresponding transmembrane proteins, may be affected by changes in dipole potential. Past studies have considered the effects of lipid composition on the dipole potential, with a focus on the headgroup type [55], ether or ester linkage type [56] and double bonds in the chain region [57]. An atomistic MD simulation study by Ding et al [50] focused on the effects of altering the lamellar vs. nonlamellar lipid composition.…”

Crude phosphorylation mixtures containing racemic lipid amphiphiles self-assemble to give stable primitive compartments

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