Asymmetric Membrane Distribution of Phosphatidylserine in Different Liposomal Preparations

Abstract We established a quantitative assay (fluorescamine-assay) to determine the distribution of phosphatidylserine (PS) in the outer and inner monolayer of mixed phosphatidylcholine/phosphatidylserine liposomes. Fluorescamine (a non-fluorescent compound) reacts with primary amino groups resultin...

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Bibliographic Details
Published in:Journal of liposome research 1999-01, Vol.9 (4), p.477-489
Main Authors: Wieland, Susanne, Schubert, Rolf, Süss, Regine Peschka
Format: Article
Language:English
Subjects:
Asymmetric liposomes
Flip-flop
Fluorescamine-assay
phosphatidylcholine
Phosphatidylserine
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Summary:Abstract We established a quantitative assay (fluorescamine-assay) to determine the distribution of phosphatidylserine (PS) in the outer and inner monolayer of mixed phosphatidylcholine/phosphatidylserine liposomes. Fluorescamine (a non-fluorescent compound) reacts with primary amino groups resulting in a fluorescent product. Fluorescamine is not able to penetrate through the liposomal membrane so only the amount of PS located in the outer monolayer is accessible for the reaction. This assay was used to study the influence of several factors in liposome preparation on liposome asymmetry. An increase in the amount of PS in the liposomal preparation leads to a decrease in the outer to inner PS ratio. This was also the case for unilamellar vesicles of decreasing size. The asymmetry of PS is only slightly influenced by the addition of phos-phatidylinositol or phosphatidylgycerol, whereas small amounts of phosphati-dylethanolamine-rhodamine-B induce a dramatic shift of PS to the inner monolayer. NBD-labeled PS shows a asymmetric distribution different from that of unlabeled PS.
ISSN:0898-2104
1532-2394
DOI:10.3109/08982109909035548