Driving Force for Crystallization of Anionic Lipid Membranes Revealed by Atomistic Simulations

Qiao, Bao Fu; Cruz, Mónica Olvera de la

doi:10.1021/jp401767c

Cited by 16 publications

(21 citation statements)

References 66 publications

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“…The observed irregular faceted shapes arise only in hexagonal crystalline lattices, where crystalline domains are separated by soft interfaces that bend to release stress. Since ionic crystalline domains also arise upon the adsorption of multivalent ions on lipids, 27 our results suggest that spherical-to-faceted reversible transitions can be induced in cationic lipid vesicles by adding (or chelating) metallic multivalent ions.…”

Section: A(b) Imentioning

confidence: 66%

Mesoscale studies of ionic closed membranes with polyhedral geometries

Cruz

2016

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Section: A(b) Imentioning

confidence: 66%

Mesoscale studies of ionic closed membranes with polyhedral geometries

Cruz

2016

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“…The simulation results show that the amphiphiles pack in hexagonal lattice in both cases, with a reduction in the area per molecule from 0.207 nm 2 (C 14 ) to 0.200 nm 2 (C 16 ). The simulations also reveal an enhancement in the van der Waals interactions from -27 k B T to -33 k B T per hydrocarbon tail when the tail length n increases from 14 to 16, which suggests a gain of ∼2 k B T per hydrocarbon atom in the crystalline membrane structure (17). The hydration of lipid bilayers has been studied previously by MD simulations in systems with charged groups such as dimyristoylphosphatidylcholine (DMPC) lipid bilayers (37), which showed that the average number of hydrogen bonds per lipid oxygen atom varies depending on its position within the lipid.…”

Section: Resultsmentioning

confidence: 82%

“…The presence of polar and hydrophobic groups in their wall envelopes and the fact that they survive at low pH values and disintegrate or become spherical (the shape of closed liquid membranes) when divalent metal ions are chelated (11,13) suggest that their crystallization is triggered by electrostatic interactions. Divalent ion-induced crystallization of anionic membranes has been recently studied (16,17), but crystallization changes induced by pH variations in bilayers are unknown. Here, we study pH effects in crystalline membranes of coassembled amphiphiles with carboxylate and dilysine headgroups, whose pK a values are about 5.5 (18) and 10 (19), respectively.…”

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confidence: 99%

Crystalline polymorphism induced by charge regulation in ionic membranes

Leung

Palmer

Kewalramani

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The crystallization of molecules with polar and hydrophobic groups, such as ionic amphiphiles and proteins, is of paramount importance in biology and biotechnology. By coassembling dilysine (+2) and carboxylate (-1) amphiphiles of various tail lengths into bilayer membranes at different pH values, we show that the 2D crystallization process in amphiphile membranes can be controlled by modifying the competition of long-range and shortrange interactions among the polar and the hydrophobic groups. The pH and the hydrophobic tail length modify the intermolecular packing and the symmetry of their crystalline phase. For hydrophobic tail lengths of 14 carbons (C 14 ), we observe the coassembly into crystalline bilayers with hexagonal molecular ordering via in situ small-and wide-angle X-ray scattering. As the tail length increases, the hexagonal lattice spacing decreases due to an increase in van der Waals interactions, as demonstrated by atomistic molecular dynamics simulations. For C 16 and C 18 we observe a reentrant crystalline phase transition sequence, hexagonalrectangular-C-rectangular-P-rectangular-C-hexagonal, as the solution pH is increased from 3 to 10.5. The stability of the rectangular phases, which maximize tail packing, increases with increasing tail length. As a result, for very long tails (C 22 ), the possibility of observing packing symmetries other than rectangular-C phases diminishes. Our work demonstrates that it is possible to systematically exchange chemical and mechanical energy by changing the solution pH value within a range of physiological conditions at room temperature in bilayers of molecules with ionizable groups.amphiphilic membranes | self-assembly | hydrophobic interaction N ature uses electrostatic interactions among positively and negatively charged groups to induce the organization of biomolecules into highly complex structures that respond to ionic changes (1, 2). The structure of the aggregates at specific ionic conditions is intimately related to its function. Therefore, understanding the mechanisms that control the structure of molecules with hydrophobic and polar groups at physiological conditions is of great importance in molecular biology and biotechnology. In particular, amphiphilic molecules that have polar ionizable groups, such as proteins and lipids, can change their structures and functions in response to the pH and the concentration of ions in the solution (3), thereby affecting their physical properties and functions. For example, the structure of lipid membranes affects the structure and activity of membrane-bound proteins (4-6). Furthermore, the intermolecular packing density and structure are known to affect the molecular diffusion rates of water and ions across membranes (7,8). Changing the packing density of molecules within membranes could also be useful for controlling encapsulation and release efficiency of molecules inside a vesicle (9). Additionally the spacing between amphiphilic molecules within a membrane may control the capacity to encapsulate or release...

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“…The biologically most relevant phases of lipid bilayers are the liquid crystal (LC) and the gel (GL) phases [9,10]. In the presence of short-chain aliphatic alcohols, a third type of phase can appear, the interdigitated (ID) phase [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…In the Lˇ form of the GL phase, the tails are tilted with respect to the bilayer normal [9,10]. In the Lˇform, the tails are oriented perpendicularly to the bilayer midplane [16].…”

Section: Introductionmentioning

confidence: 99%