Surface Potential of Lipid Monolayers with Grafted Polyethylene Glycols

Bürner, Hans; Winterhalter, Mathias; Benz, Roland

doi:10.1006/jcis.1994.1407

Cited by 19 publications

(32 citation statements)

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“…The plate vibrated at ϳ416 Hz and the signal was measured with a laboratory-built lock-in amplifier (Bürner et al, 1994). The surface potential was referenced to an Ag/AgCl electrode in the water phase.…”

Section: Measurements Of Monolayer Surface Potentialsmentioning

confidence: 99%

Interaction of Phloretin with Lipid Monolayers: Relationship between Structural Changes and Dipole Potential Change

Cseh

Benz

1999

Biophysical Journal

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Phloretin is known to adsorb to lipid surfaces and alters the dipole potential of lipid monolayers and bilayers. Its adsorption to biological and artificial membranes results in a change of the membrane permeability for a variety of charged and neutral compounds. In this respect phloretin represents a model substance to study the effect of dipole potentials on membrane permeability. In this investigation we studied the interaction of phloretin with monolayers formed of different lipids in the liquid-expanded and the condensed state. Phloretin integrated into the monolayers as a function of the aqueous concentration of its neutral form, indicated by an increase of the surface pressure in the presence of phloretin. Simultaneous recording of the surface potential of the monolayers allowed us to correlate the degree of phloretin integration and the phloretin-induced dipole potential change. Increasing the surface pressure decreased the phloretin-induced shift of the isotherms, but did not influence the phloretin-induced surface potential change. This means that phloretin adsorption to the lipid surface can occur without affecting the lipid packing. The surface potential effect of phloretin is accompanied by a change of the lipid dipole moment vector dependent on the lipid packing. This means that the relation between the surface potential change and the lipid packing cannot be described by a static model alone. Taking into account the deviations of the surface potential change versus molecular area isotherms of the experimental data to the theoretically predicted course, we propose a model that relates the area change to the dipole moment in a dynamic manner. By using this model the experimental data can be described much better than with a static model.

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Section: Measurements Of Monolayer Surface Potentialsmentioning

confidence: 99%

Interaction of Phloretin with Lipid Monolayers: Relationship between Structural Changes and Dipole Potential Change

Cseh

Benz

1999

Biophysical Journal

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“…The area per molecule for curve 1 (PEG film only) corresponds to the nominal area per PEG monomer, whereas for curves 2-5 it represents the nominal area per lipid. Curve 2 shows that the surface pressure of a pure DPhPC monolayer starts to increase at A -1.2 nm2/lipid and the collapse pressure, P -48 mN/m, occurs at -0.68 nm2/lipid (Burner et al, 1994). Curves 3-5 illustrate the P-A isotherms that result by adding 5, 10, or 20 ,g of PEG 35,000 onto the surface with an initial area 720 cm2 (i.e., before compression).…”

Section: Peg535000mentioning

confidence: 99%

Interaction of poly(ethylene-glycols) with air-water interfaces and lipid monolayers: investigations on surface pressure and surface potential

Winterhalter

Bürner

Marzinka

et al. 1995

Biophysical Journal

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We have characterized the surface activity of different-sized poly(ethylene-glycols) (PEG; M(r) 200-100,000 Da) in the presence or absence of lipid monolayers and over a wide range of bulk PEG concentrations (10(-8)-10% w/v). Measurements of the surface potential and surface pressure demonstrate that PEGs interact with the air-water and lipid-water interfaces. Without lipid, PEG added either to the subphase or to the air-water interface forms relatively stable monolayers. Except for very low molecular weight polymers (PEGs < 1000 Da), low concentrations of PEG in the subphase (between 10(-5) and 10(-4)% w/v) increase the surface potential from zero (with respect to the potential of a pure air-water interface) to a plateau value of approximately 440 mV. At much higher polymer concentrations, > 10(-1)% (w/v), depending on the molecular weight of the PEG and corresponding to the concentration at which the polymers in solution are likely to overlap, the surface potential decreases. High concentrations of PEG in the subphase cause a similar decrease in the surface potential of densely packed lipid monolayers spread from either diphytanoyl phosphatidylcholine (DPhPC), dipalmitoyl phosphatidylcholine (DPPC), or dioleoyl phosphatidylserine (DOPS). Adding PEG as a monolayer at the air-water interface also affects the surface activity of DPhPC or DPPC monolayers. At low lipid concentration, the surface pressure and potential are determined by the polymer. For intermediate lipid concentrations, the surface pressure-area and surface potential-area isotherms show that the effects due to lipid and PEG are not always additive and that the polymer's effect is distinct for the two lipids. When PEG-lipid-mixed monolayers are compressed to surface pressures greater than the collapse pressure for a PEG monolayer, the surface pressure-area and surface potential-area isotherms approach that of the lipid alone, suggesting that for this experimental condition PEG is expelled from the interface.

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“…Small unilamellar vesicles (SUVs) were prepared by drying the lipid film by blowing N 2 or in a Savant Speedvac containing the radiolabel (Ͻ0.08 mol%, giving approximately 25,000 cpm/assay) and swelling in 50 mM buffer (Tris-Cl, pH 7.4, for PLC, pH 8 for PLA 2 , and acetate buffer at pH 5.4 for PLD). Hydrated lipid was sonicated to clarity with a microtip probe fitted to a Branson sonifier (B30).…”

Section: Methodsmentioning

confidence: 99%

“…Unique interactions of PEGs with macromolecular assemblies such as biological membranes and proteins have led to several important biotechnological applications such as cell fusion and protein purification (1). Interaction of PEGs with lipid membranes is complex and the considerable phenomenology of this interaction has been reported; however, a complete description remains elusive (1)(2)(3). Precise definition of PEG-membrane interactions is complicated by the multiple effects of PEGs, viz., dehydration, osmosis, polarity, and viscosity, on several properties of membranes (1).…”

Section: Introductionmentioning

confidence: 99%