Molecular Dynamics Study on the Effect of Chain Branching on the Physical Properties of Lipid Bilayers:  Structural Stability

Abstract

In general, bilayers composed of branch-chained lipid molecules are known to have high stability and low ion permeability. To understand how chain branching affects bilayer properties on a molecular level, two molecular dynamics (MD) simulations of lipid bilayers have been undertaken in the isothermal−isobaric ensemble. The first MD simulation was carried out on the straight-chained DPPC bilayer, and the second was carried out on the branch-chained DPhPC bilayer. Chain branching reduced segmental order of the lipid chain. This would be closely related to a high gauche probability at the dihedrals in the vicinity of tert-carbons; these dihedrals brought about the chain bending at the branched segments. Due to the characteristic conformation of the branched chain, some different effects were observed: First, the probability of parallel orientation of the two chains in a lipid was reduced; second, a chain caught between the two chains of the neighboring lipid in the same leaflet of the bilayer was frequently observed. As a consequence, the branched chain showed a much lower overall rate of trans−gauche isomerization than its straight counterpart. In conclusion, the high structural stability of the branched DPhPC bilayer is attributable mainly to the slow conformational motion of the hydrophobic chain, which is clearly correlated with the observed chain “entrapment” between the lateral neighboring lipid molecules.

Mechanisms shaping cell membranes

“…Note that in our experiments we used liposomes formed of the lipids usually found in cell membranes (Folch liposomes spiked with 5% PIP2) rather than liposomes formed mostly of diphytanoyl phosphatidylcholine used in [44]. This branched-chain lipid is known to strongly promote membrane tubulation [47], more generally, has very unusual properties compared with common biological phospholipids [48,49]. …”

On the Electroporation Thresholds of Lipid Bilayers: Molecular Dynamics Simulation Investigations

“…Compared to simple phosphatidylcholine lipids, archaeal lipids have a special headgroup formed of sugar moieties but also methyl branches in the lipid tails and ether linkages instead of ester linkages between the headgroup and the carbonyl region (Ulrih et al 2009). Comparison between dipalmitoylphosphatidylcholine (DPPC)-, diphytanoyl-phosphocholine-ester (DPhPC-ester)-and diphytanoyl-phosphocholine-ether (DPhPC-ether)-based bilayers show, for instance, that branched chains increase the stability and decrease the permeability (Shinoda et al 2003(Shinoda et al , 2004b of the membrane, which are related to the slower conformational motion of the lipid tails. The difference in ester and ether linkage affects, on the other hand, the headgroup hydration and the membrane electrostatic potential.…”

Aggregation of Dodecyl 1‐Pyrenylmethyl Ether and Its Application in Structure‐Polarity Relations of Aggregates†

“…Generally, branched methyl groups will enhance the structure stability of bilayers. 18 The effect of 4a on the emission of 1 is similar to that of 3, except that the extent of enhancement of the excimer emission is more obvious (Figure 12). The influence of 4b on the emission of 1 is even more remarkable ( Figure 13).…”

“…Vitamin E acetate (4a) and benzyl phytyl ether (5) were also selected as the coaggregators to study the branch-group effect. 18 The emission of 1 was dramatically affected by cholesteryl octanoate (2a), as shown in Figure 8. The concentration of 1 was set to be 5.0 µmol/L at Φ＝0.40 dioxane-water solution (in aggregated state).…”