A differential vapor-pressure equipment for investigations of biopolymer interactions

Andersen, Kim B.; Koga, Yoshikata; Westh, Peter

doi:10.1016/s0165-022x(01)00238-x

Cited by 9 publications

(10 citation statements)

References 41 publications

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“…It may be argued, however, that the present system consists of two dispersed phases (respectively water þ glycerol and lipid þ glycerol þ water). This interpretation, which is supported by the observation (@m 1 =@m 1 ) m 3 ' 0 in water-rich suspensions of DMPC (Andersen et al, 2002), allows a simpler access to the DG trans . Thus, at equilibrium the perturbation induced by the lipid can be balanced out by a concentration change in the aqueous phase, Dm 3 , specified in Eq.…”

Section: Appendixmentioning

confidence: 53%

“…The net (free energy) effect of glycerol-DMPC interactions was measured in homemade vapor-pressure equipment, which has recently been described in detail (Andersen et al, 2002). In this setup, the vapor pressure difference between a cell and a reference is determined with high resolution (0.5 mbar at best).…”

Section: Vapor Pressure Measurementsmentioning

confidence: 99%

“…Solutions for the cell (DMPC-glycerol-water) and reference (glycerolwater) were prepared gravimetrically and '4-ml weighed aliquots were transferred to the vapor pressure equipment so that the amounts of glycerol and water in the cell and reference were approximately equal. The cell and reference were hermetically sealed and after removal of atmospheric air by repeated exposures to a previously evacuated 0.5-L flask (Andersen et al, 2002) and adjustment of the water content to yield equal glycerol:water mole ratios, DP and P ref were recorded until a constant (equilibrium) value was obtained. Details of the relevant procedures are described elsewhere (Andersen et al, 2002).…”

Section: Vapor Pressure Measurementsmentioning

confidence: 99%

“…The cell and reference were hermetically sealed and after removal of atmospheric air by repeated exposures to a previously evacuated 0.5-L flask (Andersen et al, 2002) and adjustment of the water content to yield equal glycerol:water mole ratios, DP and P ref were recorded until a constant (equilibrium) value was obtained. Details of the relevant procedures are described elsewhere (Andersen et al, 2002).…”

Section: Vapor Pressure Measurementsmentioning

confidence: 99%

“…To address this experimentally we have utilized a recently developed vapor pressure instrument (Andersen et al, 2002), along with more established calorimetric techniques, to the study of preferential interactions of glycerol and unilamellar vesicles of dimyristoyl phosphatidylcholine (DMPC). The former equipment is capable of resolving lipid-induced changes well below 0.01% of the total vapor pressure, and thus to quantify preferential interactions with satisfactory precision.…”

Section: Introductionmentioning

confidence: 99%

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Unilamellar DMPC Vesicles in Aqueous Glycerol: Preferential Interactions and Thermochemistry

Westh

2003

Biophysical Journal

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Glycerol is accumulated in response to environmental stresses in a diverse range of organisms. Understanding of favorable in vivo effects of this solute requires insight into its interactions with biological macromolecules, and one access to this information is the quantification of so-called preferential interactions in glycerol-biopolymer solutions. For model membrane systems, preferential interactions have been discussed, but not directly measured. Hence, we have applied a new differential vapor pressure equipment to quantify the isoosmotic preferential binding parameter, Gamma( micro 1), for systems of unilamellar vesicles of DMPC in aqueous glycerol. It is found that Gamma( micro 1) decreases linearly with the glycerol concentration with a slope of -0.14 +/- 0.014 per molal. This implies that glycerol is preferentially excluded from the membrane-solvent interface. Calorimetric investigations of the same systems showed that the glycerol-DMPC interactions are weakly endothermic, and the temperature of the main phase transition increases slightly (0.16 degrees C per molal) with the glycerol concentration. The results are discussed with respect to a molecular picture which takes into account both the partitioning of glycerol into the membrane and the preferential exclusion from the hydration layer, and it is concluded that the latter effect contributes about four times stronger than the former to the net interaction.

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Section: Appendixmentioning

confidence: 53%

Section: Vapor Pressure Measurementsmentioning

confidence: 99%

Section: Vapor Pressure Measurementsmentioning

confidence: 99%

Section: Vapor Pressure Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Unilamellar DMPC Vesicles in Aqueous Glycerol: Preferential Interactions and Thermochemistry

Westh

2003

Biophysical Journal

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Preferential interaction of dimethyl sulfoxide and phosphatidyl choline membranes

Westh

2004

Biochimica et Biophysica Acta (BBA) - Biomembranes

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The interaction free energy of dimethyl sulfoxide (DMSO) and two types phospholipid membranes has been assessed from measurements of vapor pressure. The lipids were phosphatidyl cholines with respectively (14:0/14:0) (DMPC) and (16:0/18:1) (POPC) fatty acid chains. The results were expressed in terms of the iso-osmolal preferential interaction parameter, Gamma(mu1), which remained negative under all experimental conditions investigated here. This shows that water-membrane interactions are more favorable than DMSO-membrane interactions. This condition is known as preferential exclusion of DMSO (or preferential hydration of the membrane), and implies that the local (interfacial) concentration of the solute is reduced compared to the bulk. At room temperature and 1 m DMSO, Gamma(mu1) was -0.3 to -0.4 for both lipids. This corresponds to a sizable reduction in the DMSO concentration in a zone including at least the first two hydration layers of the membrane. Possible origins of the preferential exclusion are discussed. As a direct consequence of the pronounced preferential exclusion, DMSO generates an osmotic stress at the membrane interface. This tends to stabilize lipid phases of low surface areas and to withdraw water from multilamellar stacks of membranes. Based on this, we suggest that the preferential exclusion of DMSO explains both the modulation of phase behavior and the constriction of multilamellar aggregates induced by this solute.

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The vapour pressure of water as a function of solute concentration above aqueous solutions of fructose, sucrose, raffinose, erythritol, xylitol, and sorbitol

Cooke¹,

Jónsdóttir²,

Westh³

2002

The Journal of Chemical Thermodynamics

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A differential vapor-pressure equipment for investigations of biopolymer interactions

Cited by 9 publications

References 41 publications

Unilamellar DMPC Vesicles in Aqueous Glycerol: Preferential Interactions and Thermochemistry

Unilamellar DMPC Vesicles in Aqueous Glycerol: Preferential Interactions and Thermochemistry

Preferential interaction of dimethyl sulfoxide and phosphatidyl choline membranes

The vapour pressure of water as a function of solute concentration above aqueous solutions of fructose, sucrose, raffinose, erythritol, xylitol, and sorbitol

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