Viscosity of Two-Dimensional Suspensions

Ding, Junqi; Warriner, Heidi E.; Zasadzinski, Joseph A.

doi:10.1103/physrevlett.88.168102

Cited by 77 publications

(134 citation statements)

References 18 publications

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“…8,[28][29][30][31][32][33][34] The distinction is important for understanding how the percolation threshold affects the kinetics of collapse. The change in viscosity of the entire film that results from a solid network 15 should affect the formation of extended folds. For the local collapse observed here, only changes of the LE domains within the solid network should be important.…”

Section: Discussionmentioning

confidence: 99%

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Distribution of Coexisting Solid and Fluid Phases Alters the Kinetics of Collapse from Phospholipid Monolayers

Yan

Hall

2006

J. Phys. Chem. B

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To determine how coexistence of liquid-expanded (LE) and tilted-condensed (TC) phases in phospholipid monolayers affects collapse from the air/water interface, we studied binary films containing dioleoyl phosphatidylcholine-dipalmitoyl phosphatidylcholine (DPPC) mixtures between 10 and 100% DPPC. Previously published results established that this range of compositions represents the LE-TC coexistence region at the equilibrium spreading pressure of 47 mN/m. When held at 49.5 mN/m on a captive bubble, the extent of total collapse fit with the LE area predicted by the phase diagram. The kinetics of collapse, however, when normalized for changes in the LE area, slowed with increasing mole fraction of DPPC. Surface area expressed as stretched exponential functions of time yielded an Avrami exponent that decreased from 1 for the homogeneously LE film to 0.3 for DPPC ≥ 70%. Microscopic studies showed that the largest changes in kinetics occurred when either alterations of the initial composition or the process of collapse induced the films to cross the percolation threshold, so that the LE phase became divided into isolated domains. Our results show that although coexisting solid and fluid phases collapse to extents that are independent, the kinetics of collapse, corrected for differences in LE area, depend on the distribution of the two phases.

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Section: Discussionmentioning

confidence: 99%

“…Although the importance of phase separation for native pulmonary surfactant is therefore uncertain, we agree that the dispersion of coexisting phases might affect the behavior of therapeutic surfactants containing simpler mixtures. 15 …”

Section: Discussionmentioning

confidence: 99%

Distribution of Coexisting Solid and Fluid Phases Alters the Kinetics of Collapse from Phospholipid Monolayers

Yan

Hall

2006

J. Phys. Chem. B

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“…6B). The similar saturated alkyl chains of both PA and hexadecanol drive cocrystallization with DPPC, and therefore greater surface viscosities (27,30,31). By contrast, the sterol ring of cholesterol cannot pack into the alkane lattice of DPPC and thus degrades the DPPC crystal, leading to disordered, low-viscosity nanodomains, which lowers the surface viscosity of the mixed films as ln η s ∝ ϕ DPPC ln η DPPC .…”

Section: (Details In Supporting Information)mentioning

confidence: 99%

“…Previous investigations of lipid mixtures with larger-scale needle viscometers have shown rapid increases in surface viscosity at higher surface pressures consistent with Eqs. 2 and 7 (26,27).…”

Section: (Details In Supporting Information)mentioning

confidence: 99%

Effect of cholesterol nanodomains on monolayer morphology and dynamics

Kim

Choi

Zell

et al. 2013

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

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At low mole fractions, cholesterol segregates into 10-to 100-nmdiameter nanodomains dispersed throughout primarily dipalmitoylphosphatidylcholine (DPPC) domains in mixed DPPC:cholesterol monolayers. The nanodomains consist of 6:1 DPPC:cholesterol "complexes" that decorate and lengthen DPPC domain boundaries, consistent with a reduced line tension, λ. The surface viscosity of the monolayer, η s , decreases exponentially with the area fraction of the nanodomains at fixed surface pressure over the 0.1-to 10-Hz range of frequencies common to respiration. At fixed cholesterol fraction, the surface viscosity increases exponentially with surface pressure in similar ways for all cholesterol fractions. This increase can be explained with a free-area model that relates η s to the pure DPPC monolayer compressibility and collapse pressure. The elastic modulus, G′, initially decreases with cholesterol fraction, consistent with the decrease in λ expected from the line-active nanodomains, in analogy to 3D emulsions. However, increasing cholesterol further causes a sharp increase in G′ between 4 and 5 mol% cholesterol owing to an evolution in the domain morphology, so that the monolayer is elastic rather than viscous over 0.1-10 Hz. Understanding the effects of small mole fractions of cholesterol should help resolve the controversial role cholesterol plays in human lung surfactants and may give clues as to how cholesterol influences raft formation in cell membranes.surface rheology | isotherms | free-volume model | AFM M inute fractions of cholesterol lead to dramatic changes in dipalmitoylphosphatidylcholine (DPPC) monolayer morphology (Figs. 1-3) (1, 2) and have equally dramatic effects on monolayer dynamic properties. One weight percent cholesterol reduces the surface viscosity, η s , of DPPC monolayers by an order of magnitude, and 2 wt% reduces η s by two orders of magnitude . Atomic force microscopy (AFM) images and microrheological data show that the cholesterol is segregated to lineactive, locally disordered nanodomains that are dispersed in and separate ordered, primarily DPPC domains. As a result, the monolayer retains many of the features of pure DPPC monolayers including a high collapse pressure, high compressibility, and so on, while having significantly lower surface viscosity. This surface viscosity effect suggests a role for cholesterol in lung surfactant (LS), a lipid-protein monolayer necessary to reduce the surface tension in the lung alveoli during respiration (Fig. S1) (3, 4). At present, even the existence of cholesterol in native LS is questioned, because the lung lavage required to harvest LS inevitably causes blood and cell debris to be coextracted, potentially contaminating LS with cholesterol (5). This lack of consensus over the role of cholesterol is reflected in the composition of replacement lung surfactants for neonatal respiratory distress syndrome (NRDS), which occurs in 20,000-30,000 premature births each year (6). Survanta and Curosurf, two clinically approved animalextract replacement surfact...

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“…3b; from Wilke et al 2010). Furthermore, Ding et al (2002) determined η S using a different technique and found that its variation with the percentage of condensed area was analogous to that of the three-dimensional dispersion of spheres in solvent with long-range repulsive interactions. Nassoy et al (1996) showed that a partially ionized latex particle inserted into a surfactant monolayer is attracted to the border of domains composed of neutral molecules in a liquid-condensed phase due to dipolar interactions.…”

Section: Effect Of Electrostatics On Membrane Rheologymentioning

confidence: 99%

Electrostatic field effects on membrane domain segregation and on lateral diffusion

Wilke

Maggio

2011

Biophys Rev

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Natural membranes are organized structures of neutral and charged molecules bearing dipole moments which generate local non-homogeneous electric fields. When subjected to such fields, the molecules experience net forces that can modify the lipid and protein organization, thus modulating cell activities and influencing (or even dominating) the biological functions. The energetics of electrostatic interactions in membranes is a long-range effect which can vary over distance within r −1 to r −3 . In the case of a dipole interacting with a plane of dipoles, e.g. a protein interacting with a lipid domain, the interaction is stronger than two punctual dipoles and depends on the size of the domain. In this article, we review several contributions on how electrostatic interactions in the membrane plane can modulate the phase behavior, surface topography and mechanical properties in monolayers and bilayers.

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Viscosity of Two-Dimensional Suspensions

Cited by 77 publications

References 18 publications

Distribution of Coexisting Solid and Fluid Phases Alters the Kinetics of Collapse from Phospholipid Monolayers

Distribution of Coexisting Solid and Fluid Phases Alters the Kinetics of Collapse from Phospholipid Monolayers

Effect of cholesterol nanodomains on monolayer morphology and dynamics

Electrostatic field effects on membrane domain segregation and on lateral diffusion

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