Dilatometry of dipalmitoyllecithin-cholesterol bilayers

Melchior, Donald L.; Scavitto, Francis J.; Steim, Joseph M.

doi:10.1021/bi00562a018

Cited by 112 publications

(79 citation statements)

References 39 publications

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“…Our Fig. 5 shows a somewhat narrow phase coexistence region between gel and liquid ordered phases that reflects the volumetric results of Melchior et al (1980), reproduced for T = 25 °C in our Figs. 1 and 2, that strongly indicate a transition region 0.20 < x < 0.29 for DPPC for all temperatures below T M .…”

Section: Phase Behavior Of Cholesterol Mixturessupporting

confidence: 86%

“…The data for DPPC(50) includes our data (solid symbols) and also data (open symbols) taken from Fig. 3 of Melchior et al (1980). The latter data are clearly noisier than our data, but the numerical values are in good agreement and they exhibit the same trend with x.…”

Section: Discussionsupporting

confidence: 68%

“…In yet additional contrast, the gel phase data for DPPC(25) in the bottom panel that were taken from Fig. 3 of Melchior et al (1980) clearly exhibit three regions that are even more obvious from their Fig. 3.…”

Section: Discussionmentioning

confidence: 92%

“…An extensive set of volumetric data for mixtures of cholesterol and DPPC was presented by Melchior et al (1980) as a function of cholesterol concentration and over a wide temperature range that included the gel phase. These data clearly showed the main chain melting phase transition as well as a region of likely phase coexistence for temperatures below the main transition.…”

Section: Introductionmentioning

confidence: 99%

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Partial molecular volumes of lipids and cholesterol

Greenwood

Tristram-Nagle

Nagle

2006

Chemistry and Physics of Lipids

212

193

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Volumetric measurements are reported for fully hydrated lipid/cholesterol bilayer mixtures using the neutral flotation method. Apparent specific volume data were obtained with the lipids DOPC, POPC and DMPC at T = 30 °C, DPPC at 50 °C, and brain sphingomyelin (BSM) at 45 and 24 °C for mole fractions of cholesterol x from 0 to 0.5. Unlike previous cholesterol mixture studies, we converted our raw data to partial molecular volume V L of the lipid and V C of the cholesterol. The partial molecular volumes were constant for POPC and DOPC as x was varied, but had sharp breaks for the other lipids at values of x C near 0.25 ± 0.05. Results for x < x C clearly exhibit the condensation effect of cholesterol on DPPC, DMPC and BSM when measured at temperatures above their main transition temperatures T M . The break points at x C are compared to phase diagrams in the literature. For x > x C the values of the partial molecular volumes of cholesterol clustered near 630 ± 10 Å 3 in all the lipids when measured for T > T M ; we suggest that this is the most appropriate measure of the bare volume of cholesterol in lipid bilayers.

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Section: Phase Behavior Of Cholesterol Mixturessupporting

confidence: 86%

Section: Discussionsupporting

confidence: 68%

Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Partial molecular volumes of lipids and cholesterol

Greenwood

Tristram-Nagle

Nagle

2006

Chemistry and Physics of Lipids

212

193

View full text Add to dashboard Cite

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“…Several spectroscopic studies reported a strong modification of phase properties of phospholipids due to the presence of cholesterol [40][41][42][43][44][45][46][47][48][49][50][51]. Depending on their relative concentration and on temperature, the phase properties of vesicles composed of binary mixtures of cholesterol and phospholipids have been described by the solid-ordered, liquid-disordered and liquid-ordered phases [52,53].…”

Section: The Homogenizing Effect Of Cholesterolmentioning

confidence: 99%

Membrane lipid domains and dynamics as detected by Laurdan fluorescence

1995

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(Laurdan) is a membrane probe of recent characterization, which shows high sensitivity to the polarity of its environment. Steady-state Laurdan excitation and emission spectra have different maxima and shape in the two phospholipid phases, due to differences in the polarity and in the amount of dipolar relaxation, ha bilayers composed of a mixture of gel and liquid-crystalline phases, the properties of Laurdan excitation and emission spectra are intermediate between those obtained in the pure phases. These spectral properties are analyzed using the generalized polarization (GP). The GP value can be used for the quantitation of each phase. The wavelength dependence of the GP value is used to ascertain the coexistence of different phase domains in the bilayer. Moreover, by following the evolution of Laurdan emission vs. time after excitation, the kinetics of phase fluctuation in phospholipid vesicles composed of coexisting gel and liquid-crystalline phases was determined. GP measurements performed in several cell lines did not give indications of coexistence of phase domains in their membranes. In natural membranes, Laurdan parameters indicate a homogeneously fluid environment, with restricted molecular motion in comparison with the phospholipid liquid-crystalline phase. The influence of cholesterol on the phase properties of the two phospholipid phases is proposed to be the cause of the phase behavior observed in na~u'al membranes. In bilayers composed of different phospholipids and various cholesterol concentrations, Laurdan response is very similar to that arising from cell membranes. In the absence of cholesterol, from the steady-state and time-resolved measurements of Laurdan in phospholipid vesicles, the condition for the occurrence of separate coexisting domains in the bilayer has been determined: the molecular ratio between the two phases must be in the range between 30% and 70%. Below and above this range, a single homogeneous phase is observed, with the properties of the more concentrated phase, slightly modified by the presence of the other. Moreover, in this concentration range, the calculated dimension of the domains is very small, between 20 and 50 A.

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Influence of Cholesterol and β‐Sitosterol on the Dynamic Behaviour of DPPC as Detected by TMA‐DPH and PyrPC Fluorescence: A Fluorescence Lifetime Distribution and Time‐Resolved Anisotropy Study

Bernsdorff

Winter

Hazlett

et al. 1995

Ber Bunsenges Phys Chem

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Fluorescence lifetime and time‐resolved anisotropy measurements on 1‐(4‐trimethylammonium‐phenyl)‐6‐phenyl‐1,3,5‐hexatriene (TMA‐DPH) and 1‐palmitoyl‐2‐[10‐(1‐pyrenyl)decanoyl]‐phosphatidylcholine (PyrPC) in lipid vesicles of 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphatidylcholine (DPPC) with and without cholesterol and β‐sitosterol, using multifrequency cross‐correlation phase fluorometry, are presented. We used TMA‐DPH and PyrPC as fluorescence probe for detecting rotational dynamics. Contrary to TMA‐DPH, which is tethered to the bilayer interface and therefore detects wobbling rotational dynamics in the interfacial and headgroup region, PyrPC senses the deeper acyl chain dynamics of the lipid bilayer. We have investigated the influence of sterol structure on the lipid dynamics. The experiments were carried out at two temperatures, one below and one above the main phase transition temperature of DPPC. Data were analyzed in terms of Lorentzian distribution functions for the fluorescence lifetime results and in terms of hindered rotation for the time‐resolved anisotropy results. We noticed, that addition of cholesterol and β‐sitosterol results in a distinct increase in average fluorescence lifetime of TMA‐DPH in both lipid phases. The rotational rates of TMA‐DPH depolarizing motions are only modestly increased in going from the gel to the liquid‐crystalline phase of DPPC. However, a marked increase in the contribution of fast rotational motions of TMA‐DPH is found as the temperature is increased through the main transition. No significant differences in rotational rates of TMA‐DPH exist between samples with embedded cholesterol or β‐sitosterol at T = 55°C. The rotational rate of TMA‐DPH in the gel state of the lipid bilayer at T = 35°C is slightly larger in the case of β‐sitosterol, however. Cholesterol and β‐sitosterol, then, have a similar effect on the contribution of fast rotational dynamics in the interfacial region of the bilayer. It decreases about 40% upon addition of 50 mol‐% sterol. The incorporation of either sterol into DPPC vesicles leads to an increase in fluorescence lifetime of PyrPC in both lipid phases. The rotational rates of PyrPC in the bilayer are an order of magnitude smaller than those of TMA‐DPH. Also the contributions of fast rotational motions significantly differ for the two fluorophores. The motional freedom in the deeper acyl chain region of DPPC in its fluid‐like state at T = 55°C is scarcely affected by addition of either sterol. However, differences in the rotational rates of the two sterols are observed for high sterol concentrations.

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Dilatometry of dipalmitoyllecithin-cholesterol bilayers

Cited by 112 publications

References 39 publications

Partial molecular volumes of lipids and cholesterol

Partial molecular volumes of lipids and cholesterol

Membrane lipid domains and dynamics as detected by Laurdan fluorescence

Influence of Cholesterol and β‐Sitosterol on the Dynamic Behaviour of DPPC as Detected by TMA‐DPH and PyrPC Fluorescence: A Fluorescence Lifetime Distribution and Time‐Resolved Anisotropy Study

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