Experimental evidence of nonexponential relaxation near the critical point of a supramolecular liquid mixture

The problem of phase instability in a binary mixture of an associating component with an inert component is analyzed from the standpoint of the theory of association equilibria. It is demonstrated that conditions of the spinodal and critical point for such a binary system are equivalent to those of the spinodal and critical point of a multicomponent mixture consisting of complex species arising by association (including nonassociated molecules). These conditions are formulated so as if species in this mixture did not participate in association and dissociation processes; configurational terms expressing changes in the content of the individual complexes depending on changes in total composition are included implicitly.

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Phase separation of binary mixtures induced by soft centrifugal fields

Physical Chemistry Chemical Physics ◽

10.1039/d0cp01527j ◽

2021 ◽

Author(s):

Thomas Zemb ◽

Rose Rosenberg ◽

Stjepan Marčelja ◽

Dirk Haffke ◽

Jean-François Dufrêche ◽

...

Keyword(s):

Phase Separation ◽

Critical Point ◽

Binary Mixtures ◽

Liquid Mixture ◽

Model System ◽

Binary Liquid Mixture ◽

Miscibility Gap ◽

Critical Fluctuations ◽

Binary Liquid

We use the model system ethanol–dodecane to demonstrate that giant critical fluctuations induced by easily accessible weak centrifugal fields as low as 2000g can be observed above the miscibility gap even far from the critical point of a binary liquid mixture.

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Finite-size transitions in complex membranes

10.1101/2020.11.05.370189 ◽

2020 ◽

Author(s):

M. Girard ◽

T. Bereau

Keyword(s):

Experimental Evidence ◽

Critical Point ◽

Finite Size ◽

Underlying Mechanism ◽

Large Temperature ◽

Strong Argument ◽

Biological Regulation ◽

Critical Manifold ◽

Critical Composition ◽

Dynamics Simulations

ABSTRACTThe lipid raft hypothesis postulates that cell membranes possess some degree of lateral organization. The last decade has seen a large amount of experimental evidence for rafts. Yet, the underlying mechanism remains elusive. One hypothesis that supports rafts relies on the membrane to lie near a critical point. While supported by experimental evidence, the role of regulation is unclear. Using both a lattice model and molecular dynamics simulations, we show that lipid regulation of a many-component membrane can lead to critical behavior over a large temperature range. Across this range, the membrane displays a critical composition due to finite-size effects. This mechanism provides a rationale as to how cells tune their composition without the need for specific sensing mechanisms. It is robust and reproduces important experimentally verified biological trends: membrane-demixing temperature closely follows cell growth temperature, and the composition evolves along a critical manifold. The simplicity of the mechanism provides a strong argument in favor of the critical membrane hypothesis.SIGNIFICANCEWe show that biological regulation of a large amount of phospholipids in membranes naturally leads to a critical composition for finite-size systems. This suggests that regulating a system near a critical point is trivial for cells. These effects vanish logarithmically and therefore can be present in micron-sized systems.

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