Characterization of the interface of binary mixed DOPC:DOPS liposomes in water: The impact of charge condensation

Lütgebaucks, Cornelis; Macias-Romero, Carlos; Roke, Sylvie

doi:10.1063/1.4974084

Cited by 50 publications

(63 citation statements)

References 39 publications

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“…The retrieved values for

are plotted on the top axis, with the initial surface potential difference

around −50 mV. This value corresponds to 0.6% of ionized lipids ( Numerical Computations ) and is consistent with the theory of charge condensation ( 35 , 48 ). Fig.…”

Section: Resultssupporting

confidence: 67%

“…Candidates for the emission of SH photons are all noncentrosymmetrically structured molecular groups ( 30 , 33 ), that is, lipids or water. Taking into account the number density difference between water and lipids and previous nonresonant SH scattering studies of liposomes ( 34 , 35 ), it is likely that the dominant contribution to the SH intensity will be from water. To test this hypothesis, we added 0.5 mM KCl to the solution.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Label-free and charge-sensitive dynamic imaging of lipid membrane hydration on millisecond time scales

Tarun

Hannesschläger

Pohl

et al. 2018

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

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SignificanceLipid bilayer membranes are responsible for compartmentalization, signaling, transport, and flow of charge in living cells. Membranes self-assemble in aqueous solutions. Without a hydrating environment, membranes cannot exist. It is therefore surprising to note that the hydrating water is neglected in most membrane-related studies. We imaged membrane-bound oriented water by means of label-free second harmonic microscopy. We tracked, on millisecond time scales, membrane domain diffusion of condensed charged lipid domains, domain structure, and the spatial distribution of charge. Real-time electrostatic membrane potential maps were constructed using nonlinear optical theory. The spatiotemporal fluctuation in the membrane potential is surprisingly large and reveals the importance of charge fluctuations on membranes.

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“…The retrieved values for

are plotted on the top axis, with the initial surface potential difference

around −50 mV. This value corresponds to 0.6% of ionized lipids ( Numerical Computations ) and is consistent with the theory of charge condensation ( 35 , 48 ). Fig.…”

Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Label-free and charge-sensitive dynamic imaging of lipid membrane hydration on millisecond time scales

Tarun

Hannesschläger

Pohl

et al. 2018

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

Self Cite

View full text Add to dashboard Cite

show abstract

“…al. 33 32 , as well as different hydrated ion sizes emphasizing the importance of specific ion effects. 32,61 Finally, biological membranes are soft, fluid interfaces which can often regulate surface charges by reorganization or counterion penetration and binding to minimize the system free energy.…”

Section: Zeta Potential Measurementsmentioning

confidence: 99%

How Well Can You Tailor the Charge of Lipid Vesicles?

et al. 2019

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Knowledge and control of surface potential (or charge) is important for tailoring colloidal interactions. In this work we compare widely used zeta potential measurements of charged lipid vesicle surface potential to direct measurements using the surface force apparatus (SFA). Our measurements show good agreement between the two techniques. On varying the fraction of anionic lipids dimyristoylphosphatidylserine (DMPS) or dimyristoylphosphatidylglycerol (DMPG) mixed with zwitterionic dimyristoylphosphatidylcholine (DMPC) from 0 to 100 mol % we observed a near-linear increase in membrane surface charge/potential up to 20-30 mol % charged lipids beyond which charge saturation occurred in physiological salt conditions. Similarly, in low salt concentrations a linear increase in 1 charge/potential was found, but only up to ~ 5-10 mol% charged lipids beyond which the surface potential/charge leveled off. While a lower degree of ionization is expected due to the lower dielectric constant ( ~ 4) of the lipid acyl chain environment, increasing intra-membrane electrostatic repulsions between neighboring lipid head groups at higher charge loading contributes to charge suppression. Measured potentials in physiological (high) salt solutions were consistent with predictions using the Gouy-Chapman-Stern-Grahame (GCSG) model of the electrical double layer with Langmuir binding of counterions, but in low salt conditions, the model significantly overestimated the surface charge/potential. The much lower ionization in low salt (maximum fraction dissociated ~ 1-2 % of total lipids) instead was consistent with counterion condensation at the bilayer surface which limited the charge/potential that could be obtained. The strong interplay between membrane composition, lipid head group ionization, solution pH and electrolyte concentration complicates exact prediction and tuning of membrane surface charge or potential for applications. However, the theoretical frameworks used in the work can be used as guidelines to understand this interplay and establish a range of achievable potentials for a system to tune or predict the response to triggers like pH and salt concentration changes.

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“…The experimental value of 0.71 nm 2 for area per lipid of DOPC/DOPS (4:1) at 297 K was reported in Ref. [51] and the experimental value of thickness to be of 3.94 nm at 303 K was reported by Novakova et al [52]. As temperature increases, atoms in the lipid structure oscillate more perpendicularly to their bonds.…”

Section: Area Per Lipidmentioning

confidence: 74%

Influence of Cholesterol on the Orientation of the Farnesylated GTP-bound KRas-4B Binding with Anionic Model Membranes

Lu¹,

Martı́²

2020

Preprint

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The Ras family of proteins is tethered to the inner leaflet of the cell membranes which play an essential role in signal transduction pathways that promote cellular proliferation, survival, growth, and differentiation. KRas-4B, the most mutated Ras isoform in different cancers, has been under extensive study for more than two decades. Here we have focused our interest on the influence of cholesterol on the orientations that KRas-4B adopts with respect to the plane of the anionic model membranes. How cholesterol in the bilayer might modulate preferences for specific orientation states is far from clear. Herein, after analyzing data from in total 4000 ns-long MD simulations for four KRas-4B systems, properties such as the area per lipid and thickness of the membrane as well as selected radial distribution functions, penetration of different moieties of KRas-4B, and internal conformational fluctuations of flexible moieties in KRas-4B have been calculated. It has been shown that high cholesterol content in the PM favors OS1, exposing the effector-binding loop for signal transduction in the cell from the atomic level. We confirm that high cholesterol in the PM helps KRas-4B mutant stay in its constitutively active state, which suggests that high cholesterol intake can increase mortality and may promote cancer progression for cancer patients. We propose that during the treatment of KRas-4B-related cancers, reducing the cholesterol level in the PM and sustaining cancer progression by controlling the plasma cholesterol intake might be taken into account in anti-cancer therapies.

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Characterization of the interface of binary mixed DOPC:DOPS liposomes in water: The impact of charge condensation

Cited by 50 publications

References 39 publications

Label-free and charge-sensitive dynamic imaging of lipid membrane hydration on millisecond time scales

Label-free and charge-sensitive dynamic imaging of lipid membrane hydration on millisecond time scales

How Well Can You Tailor the Charge of Lipid Vesicles?

Influence of Cholesterol on the Orientation of the Farnesylated GTP-bound KRas-4B Binding with Anionic Model Membranes

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