A Calorimetric Study of Phospholipid Hydration. Simultaneous Monitoring of Enthalpy and Free Energy

Markova, Natalia; Sparr, Emma; Wadsö, Lars; Wennerström, Håkan

doi:10.1021/jp001020q

Cited by 71 publications

(103 citation statements)

References 38 publications

(80 reference statements)

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“…Such a crossover between enthalpic attraction and repulsion has been experimentally observed (27,28) for gel-phase DPPC bilayers at about n w ¼ 4-5. Based on our findings, this crossover arises from the competition between enthalpic direct attraction in Fig.…”

Section: Resultsmentioning

confidence: 64%

Hydration repulsion between biomembranes results from an interplay of dehydration and depolarization

Schneck

Sedlmeier

Netz

2012

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

151

169

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Hydration repulsion dominates the interaction between polar surfaces in water at nanometer separations and ultimately prevents the sticking together of biological matter. Although confirmed by a multitude of experimental methods for various systems, its mechanism remained unclear. A simulation technique is introduced that yields accurate pressures between solvated surfaces at prescribed water chemical potential and is applied to a stack of phospholipid bilayers. Experimental pressure data are quantitatively reproduced and the simulations unveil a rich microscopic picture: Direct membrane-membrane interactions are attractive but overwhelmed by repulsive indirect water contributions. Below about 17 water molecules per lipid, this indirect repulsion is of an energetic nature and due to desorption of hydration water; for larger hydration it is entropic and suggested to involve water depolarization. This antagonistic nature and the presence of various compensating contributions indicate that the hydration repulsion is less universal than previously assumed and rather involves finely tuned surface-water interactions.solvation | MD simulation | phospholipids H ydration repulsion (HR) universally acts between wellsolvated surfaces in water and balances the van der Waals attraction in the nanometer range. It ultimately prevents the collapse of biological matter and thereby provides macromolecular assemblies with the necessary lubrication for vital functioning, even in the congested cell environment. Although complex in its nature, it is rightfully considered a fundamental force in solution chemistry and structural biology (1). HR was first quantified experimentally for stacks of charge-neutral phospholipid bilayer membranes in terms of pressure-distance curves (2-4), confirmed for two individual bilayers by the surface force apparatus (SFA) (5, 6), and is now known to universally act between nucleic acids, proteins, and polysaccharides alike (7). It exhibits an exponential decay with a decay length of a few Ångstrom (4) and as a heuristic law is nowadays commonly used in modeling the forces between polar surfaces in water (8). Although several theoretical (9-11) and simulation (12-18) studies elucidated partial aspects of the HR, none treated the full complexity of the problem and could quantitatively reproduce and explain experimental pressure-distance curves, meaning that the HR mechanism remained essentially unclear. The reason for this is obvious: Theory typically only treats one part of the problem, be it the water-water interactions, the water-surface binding, or the configurational entropy of bilayer molecules, whereas current simulation strategies account for the constant water chemical potential either in the form of a large reservoir (13-15) or by grand-canonical simulations (16,17). Due to limitations in the numerical accuracy, however, both approaches do not enable quantitative comparison of the HR pressure with experimental data. We solve this problem by introducing the thermodynamic extrapolation method (TE...

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Section: Resultsmentioning

confidence: 64%

Hydration repulsion between biomembranes results from an interplay of dehydration and depolarization

Schneck

Sedlmeier

Netz

2012

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

151

169

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“…A detailed description of the instrument is given elsewhere. [6][7][8] Several applications of this new technique have been carried out, such as studies of phospholipid hydration 10,11 and hydration of single-chain alkylglucosides. 12 The instrument consists of a calorimetric cell constituted by two vessels connected by a stainless steel tube and an isothermal double-twin microcalorimeter placed in a thermostat.…”

Section: Methodsmentioning

confidence: 99%

The Hydration of a DNA−Amphiphile Complex

et al. 2004

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We present measurements of isothermal DNA-hexadecyltrimethylammonium (DNACTA) complex and pure DNA hydration at 25°C using a sorption microcalorimeter. This calorimeter provides simultaneous measurement of (i) water activity (sorption isotherms) and (ii) the partial molar enthalpy of water as a function of water uptake. For pure DNA, hydration is exothermic over the studied concentration range and we find an approximately linear relation between the partial molar enthalpy and the partial molar free energy. A kink in the isotherm appears at 20.0 ( 0.3 water molecules per base pair for a water activity of 0.80, consistent with A-B transition of the DNA. There is no detectable heat effect associated with this transition. At low water contents, the hydration of the DNACTA (1:1) complex is exothermic as for the pure DNA, but after incorporation of the first 7.0 ( 0.1 water molecules, the enthalpy changes sign. At 22 water molecules per base pair, the enthalpy levels off to 2.7 ( 0.2 kJ/mol. In a separate experiment, the swelling limit for the DNACTA complex was found to be 27 ( 1 waters per base pair. The DNACTA complex is arranged in a hexagonal structure. We propose a model for the DNACTA complex based on the packing of the components in an electroneutral way consisting of six DNA helices, presumably in an A configuration, placed around a central CTA + cylinder. The hydration of the complex is seen as a balance between the attractive electrostatic interaction causing the formation of the complex and a repulsive component arising from a hexagonal deformation of CTA + cylinders. An important contribution to the partial molar enthalpy of water comes, in this interpretation, from the release of conformational constraints of the CTA ion alkyl chains.

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“…18 In Figure 3 characterization of the binary OG-water and DMPC-water systems. [19][20][21] This can be used to illustrate the simplest scenario:…”

Section: Water -Octyl Glucoside -Phospholipidmentioning

confidence: 99%

Lipid phase behaviour under steady state conditions

2013

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12177), we here analyse the phenomenon for threecomponent systems. The relevant transport equations are derived, and explicit results are given for some limiting cases. Then the formalism is applied conceptually to four different aqueous lipid systems, which in addition to water and a phospholipid contain i) octyl glucoside, ii) urea, iii) heavy water, iv) sodium cholate as the third component. These four cases are chosen to illustrate i) a method to use a micelle 15 former to transport lipid to the interface where a multi-lamellar structure can form; ii) to use a co-solvent to inhibit the formation of a gel phase at the interface; iii) a method to form pure phospholipid multilamellar structures at the interface; iv) a method to form a sequence of phases in the interfacial region. These four cases all have the character of theoretically based conjectures and it remains to investigate experimentally whether or not the conditions can be realized in practice.

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A Calorimetric Study of Phospholipid Hydration. Simultaneous Monitoring of Enthalpy and Free Energy

Cited by 71 publications

References 38 publications

Hydration repulsion between biomembranes results from an interplay of dehydration and depolarization

Hydration repulsion between biomembranes results from an interplay of dehydration and depolarization

The Hydration of a DNA−Amphiphile Complex

Lipid phase behaviour under steady state conditions

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