Calorimetric Studies of Dilute Aqueous Suspensions of Bilayers Formed from Synthetic l-α-Lecithins

Hinz, Hans‐Jürgen; Sturtevant, Julian M.

doi:10.1016/s0021-9258(19)44765-0

Cited by 493 publications

(139 citation statements)

References 14 publications

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“…The specific heat anomaly calculated from AKm is shown in Fig. 5 together with the similar calculation from Aap (30) and the direct measurement of ACp by a differential scanning calorimeter (DSC) (1,30). In the calculation of Aap and ACp from the data of Wilkinson and Nagle (30), the anomalous part was determined assuming that the temperature dependence above 600C is the base line free from the transition anomaly.…”

Section: Discussionmentioning

confidence: 97%

Thermodynamic properties of the lipid bilayer transition. Pseudocritical phenomena

Mitaku¹,

Jippo²,

Kataoka³

1983

Biophysical Journal

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Ultrasonic relaxation of multilamellar liposomes formed from dipalmitoylphosphatidylcholine was measured near the gel-to-liquid crystal transition by a differential ultrasonic resonator. The relaxation time and strength increased remarkably near the transition temperature, indicating a pseudocritical phenomenon. A quantitative analysis of the relaxation in terms of thermodynamic relationships between specific heat, thermal-expansion coefficient, and compressibility showed that more than 90% of the total endothermic heat of the transition arises from the latent heat. The temperature dependence of the ultrasonic relaxation parameters was also analyzed by the Landau theory; we obtain a small but finite difference, 0.6 degree C, between the pseudocritical temperature and the transition temperature. These results provide a quantitative description of both the first-order and second-order characters of the gel-to-liquid crystal transition.

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Section: Discussionmentioning

confidence: 97%

Thermodynamic properties of the lipid bilayer transition. Pseudocritical phenomena

Mitaku¹,

Jippo²,

Kataoka³

1983

Biophysical Journal

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“…There appears to be a second structural change at 5-10°C. This may be due to a pre-transition of the type observed about 10°C below the main transition in lecithin-water mixtures (Hinz and Sturtevant, 1972). Alternatively, and more likely, the two changes may represent the beginning and end of a single broad transition or be the result of a complex phase diagram originating from the properties of a two-component mixture.…”

Section: Discussionmentioning

confidence: 99%

“…As the temperature of the lipids is raised above the transition temperature, a gel-to-liquid crystalline phase change occurs which can affect transport processes (Overath et al, 1971) and enzyme activity (Eletr et al, 1973). Phase transitions have been studied extensively in model systems of membrane lipids dispersed in an aqueous phase (e.g., Ladbrooke and Chapman, 1969;Melchior and Morowitz, 1972;Hinz and Sturtevant, 1972;Tardieu et al, 1973). Few studies, however, have been made of phase transitions in planar bilayer membranes of the type first described by Mueller et al (1962).…”

Section: Introductionmentioning

confidence: 99%

Phase transitions in planar bilayer membranes

White¹

1975

Biophysical Journal

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Temperature-dependent structural changes in planar bilayer membranes formed from glycerol monooleate (GMO) dispersed in various n-alkane solvents (C12-C17) have been studied using precise measurements of specific geometric capacitance (Cg). Cg generally increases as temperature (T) decreases. A change in the slope of Cg(T) occurs between 15 and 18 degrees C for all solvent systems examined. Measurements of the interfacial tension (gamma) of the bulk GMO-alkane dispersions against 0.1 M NaCl show that gamma generally decreases with decreasing temperature. The data can be fitted with two straight lines of different slope which intersect on the average at 17 degrees C. Pagano et al. (1973, Science (Wash. D.C.). 181:557) have shown using calorimetry that GMO has a phase transition at about 15 degrees C. Thus, the changes in Cg and gamma with temperature are likely to result from a GMO phase transition. A second structural change is observed to occur between 5 and 10 degrees C which has not been detected calorimetrically. Calculations of Cg based on various estimates of the hydrocarbon dielectric coefficient (epsilon-b) and/or hydrocarbon thickness (delta-b) leads to models for the structure of the bilayer above and below the phase transition temperature.

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“…A current and popular hypothesis is that cell membranes contain dynamic submicrometer "lipid raft" domains that are enriched in certain kinds of lipids and protein species and phase separated from the rest of the membrane [2]. Since the earliest studies of phase separation on membranes, binary mixtures of lipids having long saturated acyl chains together with lipids having short or unsaturated chains have proven to be important model systems [3,4]. Upon cooling these binary systems from a state in which the two lipid components are uniformly mixed in a fluid phase, two phases emerge.…”

Section: Introductionmentioning

confidence: 99%

Atomic Force Microscopy of Phase Separation on Ruptured, Giant Unilamellar Vesicles, and a Mechanical Pathway for the Co-Existence of Lipid Gel Phases

Jiang

Pryse

Singamaneni

et al. 2019

Journal of Biomechanical Engineering

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Phase separation of lipid species is believed to underlie formation of lipid rafts that enable the concentration of certain surface receptors. However, the dynamics and stabilization of the resulting surface domains are unclear. We developed a methodology for collapsing giant unilamellar vesicles (GUVs) into supported bilayers in a way that keeps membrane nanodomains stable and enables their imaging. We used a combination of fluorescence and atomic force microscopy (AFM) of this system to uncover how a surprising phase separation occurs on lipid vesicles, in which two different gel phases of the same lipid co-exist. This unusual phase behavior was evident in binary GUVs containing 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) and either 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). The approach showed that one of the phases is stabilized by lipid patches that become ejected from the membrane, thereby enabling the stabilization of what would otherwise be a thermodynamically impossible coexistence. These results show the utility of AFM on collapsed GUVs, and suggest a possible mechanical mechanism for stabilization of lipid domains.

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Calorimetric Studies of Dilute Aqueous Suspensions of Bilayers Formed from Synthetic l-α-Lecithins

Cited by 493 publications

References 14 publications

Thermodynamic properties of the lipid bilayer transition. Pseudocritical phenomena

Thermodynamic properties of the lipid bilayer transition. Pseudocritical phenomena

Phase transitions in planar bilayer membranes

Atomic Force Microscopy of Phase Separation on Ruptured, Giant Unilamellar Vesicles, and a Mechanical Pathway for the Co-Existence of Lipid Gel Phases

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