Journal of Fluorescence

, Volume 2, Issue 3, pp 167–174

Packing of phospholipid vesicles studied by oxygen quenching of Laurdan fluorescence

  • Tiziana Parasassi
  • Enrico Gratton
Article

Abstract

Steady-state fluorescence oxygen quenching experiments were performed on phospholipid vesicles where 2-dimethylamino-6-lauroylnaphthalene (Laurdan) was inserted. The quenching efficiency was found to be much higher in vesicles in the liquid-crystalline phase with respect to the gel phase, by a factor of about 50. Since the oxygen solubility in the two phospholipid phases can differ at most by a factor of 4 based on literature values, we concluded that oxygen diffusion must be responsible for the great difference in the quenching efficiency. A relatively high quenching efficiency was also found in vesicles composed of equimolar gel and liquid-crystalline phospholipids. Simulations were performed using the linear superposition of the properties of the pure phases to demonstrate that, in the case of vesicles composed of coexisting phases, the diffusional properties of oxygen in each phase are largely modified by the presence of the other. The addition of 10 mol% cholesterol to the gel phase rendered Laurdan fluorescence approximately as quenchable as in the equimolar mixture of the two phases. This result points out that molecules such as cholesterol, which introduce packing defects in the bilayer, favor oxygen diffusion. From the oxygen quenching experiments and using the properties of generalized polarization, the rate of Laurdan dipolar relaxation can be estimated.

Key Words

Generalized polarization Laurdan oxygen phospholipids quenching 

Abbreviations used

Laudran

2-dimethylamino-6-lauroylnapthalene

DLPC

dilauroylphosphatidylcholine

DMPC

dimyristoylphosphatidylcholine

DPH

1,6-diphenyl-1,3,5-hexatriene

DPPC

dipalmitoylphosphatidylcholine

TNS

p-tofuidinyl-6-naphthalene sulfonic acid

PBS

phosphate-buffered saline solution

GP

generalized polarization

NMR

nuclear magnetic resonance

EPR

electron paramagnetic resonance

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Copyright information

© Plenum Publishing Corporation 1992

Authors and Affiliations

  • Tiziana Parasassi
    • 1
  • Enrico Gratton
    • 2
  1. 1.Istituto di Medicina SperimentaleCNRRomaItalia
  2. 2.Laboratory for Fluorescence DynamicsUniversity of Illinois at Urbana-ChampaignUrbana

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