Understanding the Hofmeister Effect in Interactions between Chaotropic Anions and Lipid Bilayers:  Molecular Dynamics Simulations

Sachs, Jonathan N.; Woolf, Thomas B.

doi:10.1021/ja0355729

Cited by 133 publications

(163 citation statements)

References 22 publications

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“…[39] A strong nonspecific penetration of anions into the lipid phases has been found in recent molecular dynamics simulations by Sachs and Woolf. [40] Adsorption through strong local binding or dispersion forces plays a role in the interaction of anions with lipid interfaces. [41] Our results, based on increasing area for the DPPC monolayer from left to right, show the order of the series as follows: SO 4 2À , Cl À , Br À , NO 3 À .…”

Section: Resultsmentioning

confidence: 99%

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

Wang

2017

Environ. Chem.

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Environmental context. Lipids released from lysis of phytoplankton cells are enriched in the sea surface microlayer. Such surface-active organics can be transferred through bursting bubbles to sea-spray aerosols where they can influence atmospheric chemistry. The results presented here suggest that phospholipids combine more readily with SO 4 2À than with Br À , leading to enrichment of organic-coated sulfate salts in marine aerosols.Abstract. Inorganic salts and organic matter are known to be present at higher levels in the sea surface microlayer and marine aerosols; however, the impact of common anions on their surface properties is not well understood. Here, a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer was enriched with the sodium and ammonium salts of different anions (Br À , Cl À , NO 3 À , SO 4 2À , CH 3 COO À , and HCO 3 À ), and the effects on the surface properties of the monolayer were investigated. The monolayer phase behaviour and the structure of the lipid phases were studied by surface pressure-area (p-A) isotherms and infrared reflection-absorption spectroscopy (IRRAS). The presence of salts in the subphase was found to increase the surface pressure of the DPPC monolayer at a fixed area per molecule. The effect of the anions follows the order of the Hofmeister series. The higher concentration of salt solution caused the p-A isotherm to shift to larger area. The IRRAS spectra demonstrate that the ordering of the DPPC molecules in the liquid condensed phase remains essentially unaffected, even at higher electrolyte concentrations. DPPC molecules combined with SO 4 2À could be transferred from the ocean to sea spray aerosol. The present study finds that the anions have significant influence on the surface organisation and, consequently, the interfacial properties, of the surface-active species at the air-water interface, a finding that has further implications for atmospheric aerosol nucleation.

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Section: Resultsmentioning

confidence: 99%

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

Wang

2017

Environ. Chem.

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“…Using the all-atom CHARMM (Chemistry at HARvard Molecular Mechanics) parameter set 27, no complexation of Na + with the lipid carbonyl oxygens has been reported. 43,45,57 In contrast, using the "Berger lipids", i.e., variants of united-atom force-fields based on refs 70, 96, and 97, tight binding of Na + ions to the lipid carbonyl oxygens is found. 33,42,46,[50][51][52][53]55,56,58,61 Due to the different nature of these two force-fields, simulations using CHARMM27 lipids need to be performed with the area of the bilayer fixed, whereas Berger lipids allow simulations in the NpT ensemble, such that the bilayer can adjust its area to agree with the thermodynamic parameters.…”

Section: Discussionmentioning

confidence: 99%

“…[28][29][30][31][32][33][34][35][36][37][38][39][40][41] As for molecular-level computational studies, the increase in computing power in the past few years has made it possible to extend computer simulations beyond the relatively long relaxation times of tens to hundreds of nanoseconds required for equilibration of ions in lipid/water systems. Although most computational studies by far have focused on the effects of salt ions on zwitterionic (neutral) lipid bilayers, 33,[42][43][44][45][46][47][48][49][50][51][52][53] there is also an increasing number of studies on anionic [54][55][56][57][58][59] and cationic 60,61 lipid bilayers. Most simulations have addressed the effect of ions on the structural and electrostatic properties of lipid membranes.…”

Section: Introductionmentioning

confidence: 99%

Ion Dynamics in Cationic Lipid Bilayer Systems in Saline Solutions

et al. 2009

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Positively charged lipid bilayer systems are a promising class of nonviral vectors for safe and efficient gene and drug delivery. Detailed understanding of these systems is therefore not only of fundamental but also of practical biomedical interest. Here, we study bilayers comprising a binary mixture of cationic dimyristoyltrimethylammoniumpropane (DMTAP) and zwitterionic (neutral) dimyristoylphosphatidylcholine (DMPC) lipids. Using atomistic molecular dynamics simulations, we address the effects of bilayer composition (cationic to zwitterionic lipid fraction) and of NaCl electrolyte concentration on the dynamical properties of these cationic lipid bilayer systems. We find that, despite the fact that DMPCs form complexes via Na + ions that bind to the lipid carbonyl oxygens, NaCl concentration has a rather minute effect on lipid diffusion. We also find the dynamics of Cl -and Na + ions at the water-membrane interface to differ qualitatively. Cl -ions have well-defined characteristic residence times of nanosecond scale. In contrast, the binding of Na + ions to the carbonyl region appears to lack a characteristic time scale, as the residence time distributions displayed power-law features. As to lateral dynamics, the diffusion of Na + ions within the water-membrane interface consists of two qualitatively different modes of motion: very slow diffusion when ions are bound to DMPC, punctuated by fast rapid jumps when detached from the lipids. Overall, the prolonged dynamics of the Na + ions are concluded to be interesting for the physics of the whole membrane, especially considering its interaction dynamics with charged macromolecular surfaces.

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“…Numerous examples for unspecific interactions of chaotropic anions with biological membranes are also known;7, 162, 168, 169, 170, 171, 172, 173, 174 in particular, their membrane‐disrupting properties are noteworthy 171, 172. Gabel and co‐workers investigated the interaction between dodecaborate cluster dianions and lipid bilayers;34, 35, 36, 175 at high salt concentrations they observed changes in the morphology of liposomes as well as bilayer leakage (see Figure 8 for an example).…”

Section: Examplesmentioning

confidence: 99%

The Chaotropic Effect as an Assembly Motif in Chemistry

2018

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Following up on scattered reports on interactions of conventional chaotropic ions (for example, I−, SCN−, ClO4 −) with macrocyclic host molecules, biomolecules, and hydrophobic neutral surfaces in aqueous solution, the chaotropic effect has recently emerged as a generic driving force for supramolecular assembly, orthogonal to the hydrophobic effect. The chaotropic effect becomes most effective for very large ions that extend beyond the classical Hofmeister scale and that can be referred to as superchaotropic ions (for example, borate clusters and polyoxometalates). In this Minireview, we present a continuous scale of water–solute interactions that includes the solvation of kosmotropic, chaotropic, and hydrophobic solutes, as well as the creation of void space (cavitation). Recent examples for the association of chaotropic anions to hydrophobic synthetic and biological binding sites, lipid bilayers, and surfaces are discussed.

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Understanding the Hofmeister Effect in Interactions between Chaotropic Anions and Lipid Bilayers: Molecular Dynamics Simulations

Cited by 133 publications

References 22 publications

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

Ion Dynamics in Cationic Lipid Bilayer Systems in Saline Solutions

The Chaotropic Effect as an Assembly Motif in Chemistry

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