Minimal Effect of Lipid Charge on Membrane Miscibility Phase Behavior in Three Ternary Systems

Blosser, Matthew C.; Starr, Jordan B.; Turtle, Cameron W.; Ashcraft, J. Nathan; Keller, Sarah L.

doi:10.1016/j.bpj.2013.04.055

Cited by 49 publications

(69 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As mentioned above, it was reported in the past experiments 19,21,22,23 that phase separation of other mixtures containing negatively charged unsaturated lipids was suppressed similarly to our DOPG (-) /DPPC result.…”

Section: Discussionsupporting

confidence: 88%

Charge-induced phase separation in lipid membranes

et al. 2014

View full text Add to dashboard Cite

The phase separation in lipid bilayers that include negatively charged lipids is examined experimentally. We observed phase-separated structures and determined the membrane miscibility temperatures in several binary and ternary lipid mixtures of unsaturated neutral lipid, dioleoylphosphatidylcholine (DOPC), saturated neutral lipid, dipalmitoylphosphatidylcholine (DPPC), unsaturated charged lipid, dioleoylphosphatidylglycerol (DOPG (-) ), saturated charged lipid, dipalmitoylphosphatidylglycerol (DPPG (-) ), and cholesterol. In binary mixtures of saturated and unsaturated charged lipids, the combination of the charged head with the saturation of hydrocarbon tail is a dominant factor for the stability of membrane phase separation. DPPG (-) enhances phase separation, while DOPG (-) suppresses it. Furthermore, the addition of DPPG (-) to a binary mixture of DPPC/cholesterol induces phase separation between DPPG (-) -rich and cholesterol-rich phases. This indicates that cholesterol localization depends strongly on the electric charge on the hydrophilic head group rather than on the ordering of the hydrocarbon tails. Finally, when DPPG (-) was added to a neutral ternary system of DOPC/DPPC/Cholesterol (a conventional model of membrane rafts), a three-phase coexistence was produced. We conclude by discussing some qualitative features of the phase behaviour in charged membranes using a free energy approach.

show abstract

Section: Discussionsupporting

confidence: 88%

Charge-induced phase separation in lipid membranes

et al. 2014

View full text Add to dashboard Cite

show abstract

“…[1][2][3][4][5][6] These membrane systems are widely considered as model systems that mimic the composition of the general mammalian cell plasma membrane. Observations of the same macroscopic miscibility transitions in cell membrane blebs provide compelling confirmation that this is an inherent property of cell membrane lipids.…”

Section: Introductionmentioning

confidence: 99%

Live Cell Plasma Membranes Do Not Exhibit a Miscibility Phase Transition over a Wide Range of Temperatures

et al. 2015

View full text Add to dashboard Cite

Lipid:cholesterol mixtures derived from cell membranes, as well as their synthetic reconstitutions, exhibit well defined miscibility phase transitions and critical phenomena near physiological temperatures. This suggests that lipid:cholesterol-mediated phase separation plays a role in the organization of live cell membranes. However, macroscopic lipid phase separation is not generally observed in cell membranes and the degree to which properties of isolated lipid mixtures are preserved in the cell membrane remain unknown. A fundamental property of phase transitions is that the variation of tagged particle diffusion with temperature exhibits an abrupt change as the system passes through the transition, even when the two phases are distributed in a nanometer-scale emulsion. We support this using a variety of Monte-Carlo and atomistic simulations on model lipid membrane systems. However, temperature dependent fluorescence correlation spectroscopy of labeled lipids and membrane-anchored proteins in live cell membranes show a consistently smooth increase of the diffusion coefficient as a function of temperature. We find no evidence of a discrete miscibility phase transition throughout a wide range of temperatures: 14 -37 °C. This contrasts the behavior of giant plasma membrane vesicles (GPMVs) blebbed from the same cells, which do exhibit phase transitions and macroscopic phase separation. Fluorescence lifetime analysis of a DiI probe in both cases reveals a significant environmental difference between the live cell and the GPMV. Taken together, these data suggest the live cell membrane may avoid the miscibility phase transition inherent to its lipid constituents by actively regulating physical paramters, such as tension, in the membrane.

show abstract

“…Flip-flop rates could be controlled by electroporation [46,47], topological defects [7], or even synthetic scramblase enzymes [14], while an external field can be provided by a substrate or, for charged lipid mixtures, an electric field. Charge may have minimal side effects on miscibility [48], perhaps most closely approximating our idealised symmetry-breaking field (Eq. 9).…”

Section: Discussionmentioning

confidence: 99%

Effects of passive phospholipid flip-flop and asymmetric external fields on bilayer phase equilibria

Williamson

Olmsted

2018

Preprint

View full text Add to dashboard Cite

Compositional asymmetry between the leaflets of bilayer membranes is known to couple strongly to their phase behaviour, in addition to having important effects on, e.g., mechanical properties and protein activity. We address how phase behaviour is affected by passive phospholipid flip-flop, such that the compositional asymmetry is not fixed. We predict transitions from "pre flip-flop" behaviour to a restricted set of phase equilibria that can persist in the presence of passive flipflop. Surprisingly, such states are not necessarily symmetric. We further account for external symmetry-breaking, such as a preferential substrate interaction, and show how this can stabilise strongly asymmetric equilibrium states. Our theory explains several experimental observations of flip-flop mediated changes in phase behaviour, and shows how domain formation and compositional asymmetry can be controlled in concert, by manipulating passive flip-flop rates and applying external fields.

show abstract

Minimal Effect of Lipid Charge on Membrane Miscibility Phase Behavior in Three Ternary Systems

Cited by 49 publications

References 62 publications

Charge-induced phase separation in lipid membranes

Charge-induced phase separation in lipid membranes

Live Cell Plasma Membranes Do Not Exhibit a Miscibility Phase Transition over a Wide Range of Temperatures

Effects of passive phospholipid flip-flop and asymmetric external fields on bilayer phase equilibria

Contact Info

Product

Resources

About