The phase transition in phospholipid vesicles probed by the positron annihilation lifetime technique

McMahon, Philip L.; Graf, George; Glass, J. Edward

doi:10.1016/0375-9601(79)90504-8

Cited by 6 publications

(15 citation statements)

References 12 publications

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“…This trend in lifetime agrees well with past studies [34][35][36]49 with a Dt oPs of 400 ps consistent with that reported by both McGrath et al 35 and Jean et al, 34 although the absolute lifetime values differ. Whilst these systems have previously been studied in the literature, interpretation and comparison of results is difficult, as the evolution of instrumentation and data analysis methods over the decades has made it difficult to directly compare the available data sets.…”

Section: Biomembrane Phase Transitions By Positron Annihilation Lifetsupporting

confidence: 92%

“…This bound state is referred to as a ''positronium'' that may exist in two ground states, i.e. [31][32][33][34][35][36][37] However studies of this nature have been sparse, with many of the observations conflicting due to differences in data analysis and experimental design, so that it is difficult to extract physicochemically-meaningful comparative information from these studies. 12 oPs is of the greatest interest as the primary mechanism of annihilation is via ''pick-off'' with electrons in low electron density regions.…”

Section: Introductionmentioning

confidence: 99%

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Packing and mobility of hydrocarbon chains in phospholipid lyotropic liquid crystalline lamellar phases and liposomes: characterisation by positron annihilation lifetime spectroscopy (PALS)

Dong

Fong

Waddington

et al. 2015

Phys. Chem. Chem. Phys.

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Lipid lamellar mesophases and their colloidal dispersions (liposomes) are increasingly being deployed in vivo as drug delivery vehicles, and also as models of biological membranes in fundamental biophysics studies. The permeability and diffusion of small molecules such as drugs is accommodated by a change in local curvature and molecular packing (mesophase behaviour) of the bilayer membrane molecules. Positron annihilation lifetime spectroscopy (PALS) is capable of providing in situ molecular level information on changes in free volume and void space arising from such changes in a non-perturbative manner. In this work PALS was used to systematically characterise the temperature-induced melting transitions (Tm) of saturated and unsaturated phospholipid-water systems while systematically varying lipid chain length, as both bulk lamellar mesophase and as aqueous colloidal dispersions (liposomes). A four-component fit of the data was used that provides separate PALS lifetimes for the aqueous (τ3) and organic domains (τ4). The oPs lifetime (τ4), for the lamellar phases of DSPC (C18:0), DPPC (C16:0), DMPC (C14:0) and DLPC (C12:0) was found to be independent of chain length, with characteristic lifetime value τ4 ∼ 3.4 ns. τ4 is consistently larger in the dispersed liposomes compared to the bulk mesophases, suggesting that the hydrocarbon chains are more mobile. The use of contemporary and consistent analytical approaches as described in this study is the key to future deployment of PALS to interrogate the in situ influence of drugs on membrane and cellular microenvironments.

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Section: Biomembrane Phase Transitions By Positron Annihilation Lifetsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Packing and mobility of hydrocarbon chains in phospholipid lyotropic liquid crystalline lamellar phases and liposomes: characterisation by positron annihilation lifetime spectroscopy (PALS)

Dong

Fong

Waddington

et al. 2015

Phys. Chem. Chem. Phys.

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“…19,20,22,57,85,86 The destructive effect of positrons on membranes is negligible and the degree of perturbation caused by the positron probe minimal, with the typical concentration of positron probes required, 10 À16 M, being several orders of magnitude less than conventional chemical probes. 19,20,22,57,85,86 The destructive effect of positrons on membranes is negligible and the degree of perturbation caused by the positron probe minimal, with the typical concentration of positron probes required, 10 À16 M, being several orders of magnitude less than conventional chemical probes.…”

Section: Application Of Pals To Biologically Relevant Systemsmentioning

confidence: 99%

Positron annihilation lifetime spectroscopy (PALS): a probe for molecular organisation in self-assembled biomimetic systems

Fong

Dong

Hill

et al. 2015

Phys. Chem. Chem. Phys.

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Positron annihilation lifetime spectroscopy (PALS) has been shown to be highly sensitive to conformational, structural and microenvironmental transformations arising from subtle geometric changes in molecular geometry in self-assembling biomimetic systems. The ortho-positronium (oPs) may be considered an active probe that can provide information on intrinsic packing and mobility within low molecular weight solids, viscous liquids, and soft matter systems. In this perspective we provide a critical overview of the literature in this field, including the evolution of analysis software and experimental protocols with commentary upon the practical utility of PALS. In particular, we discuss how PALS can provide unique insight into the macroscopic transport properties of several porous biomembrane-like nanostructures and suggest how this insight may provide information on the release of drugs from these matrices to aid in developing therapeutic interventions. We discuss the potentially exciting and fruitful application of this technique to membrane dynamics, diffusion and permeability. We propose that PALS can provide novel molecular level information that is complementary to conventional characterisation techniques.

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“…The experimental techniques used in characterizing this transition include x-ray diffraction, differential scanning calorimetry, fluorescent intensity measurements, electron spin resonance, and nuclear magnetic resonance. Recently, the positron probe method has also proven to be useful in studying the phospholipid phase transition (McMahon et al, 1979).…”

Section: Introductionmentioning

confidence: 99%

Gamma-gamma directional correlation study of model membranes

Withnell¹,

Glass²,

Graf³

1982

Biophysical Journal

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Measurements of the perturbed gamma-gamma directional correlation were made for the 173-247 keV cascade in 111Cd at the In ion site in dipalmitoylphosphatidylcholine liposomes. A time-dependent electric quadrupole interaction was observed. Below the order in equilibrium fluid phase transition temperature the exponential damping coefficient was lambda 2 = 0.033 +/- 0.007 ns-1. Above the transition temperature the coefficient was lambda 2 = 0.015 +/- 0.006 ns-1 indicating a twofold increase in molecular mobility in the disordered phase. Absolute values for the motional correlation time, tau c, were estimated to be on the order of a few nanoseconds. The presence of cholesterol was found to cause no significant difference in the molecular mobility of the phosphatidylcholine head groups in the ordered and fluid states.

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The phase transition in phospholipid vesicles probed by the positron annihilation lifetime technique

Cited by 6 publications

References 12 publications

Packing and mobility of hydrocarbon chains in phospholipid lyotropic liquid crystalline lamellar phases and liposomes: characterisation by positron annihilation lifetime spectroscopy (PALS)

Packing and mobility of hydrocarbon chains in phospholipid lyotropic liquid crystalline lamellar phases and liposomes: characterisation by positron annihilation lifetime spectroscopy (PALS)

Positron annihilation lifetime spectroscopy (PALS): a probe for molecular organisation in self-assembled biomimetic systems

Gamma-gamma directional correlation study of model membranes

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