Source:http://linkedlifedata.com/resource/pubmed/id/20722430
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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
18
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| pubmed:dateCreated |
2010-9-14
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| pubmed:abstractText |
The temperature-dependent fluorescence quenching of an amphiphilic palmitoyl derivative of 2,3-diazabicyclo[2.2.2]oct-2-ene (Fluorazophore-L) by ?-tocopherol (?-Toc) has been determined in liposomes composed of a saturated lipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The mutual lateral diffusion coefficients (D(L)) were extracted according to a laterally diffusion-controlled dynamic quenching model. Three distinct temperature regimes were identified: one between 65 and 39 °C, where the lateral diffusion coefficients were in the range of 10(-7) cm(2) s(-1) and the lifetime of the probe was monoexponential in the absence of ?-Toc, a second one between 39 and 30 °C, where the lateral diffusion coefficients were in the range of 10(-8) cm(2) s(-1) and the lifetime of the probe was biexponential in the absence of ?-Toc, and a third one below 30 °C, in which no diffusion was detectable, suggesting D(L) < 10(-9) cm(2)s (-1). These temperature domains were assigned, supported by differential scanning calorimetry (DSC) measurements, to the liquid-crystalline, ripple, and solid-gel phases of DPPC liposomes in the presence of the two additives. The absolute values of the individual lateral diffusion coefficients (taken as (1)/(2) of the D(L) values) of the Fluorazophore-L/?-Toc (ca. 2.5 × 10(-7) cm(2) s(-1) at 52 °C) couple demonstrates that ?-Toc does not diffuse at an unexpectedly high rate in comparison to the self-diffusion of DPPC (1.5 × 10(-7) cm(2) s(-1) at 52 °C). However, diffusion in DPPC liposomes is distinctly slower than that in POPC ones (e.g., D(L) = 4.9 × 10(-7) cm(2) s(-1) versus 6.4 × 10(-7) cm(2) s(-1) at 50 °C), with an activation energy of 49 ± 5 kJ mol(-1) (value for POPC: 47 ± 5 kJ mol(-1)), in the temperature range of the liquid-crystalline phase. Diffusion in the ripple phase, that is, below the main phase transition temperature, was found to be non-negligible, with an apparent activation energy of 175 ± 50 kJ mol(-1).
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:citationSubset |
IM
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| pubmed:chemical | |
| pubmed:status |
MEDLINE
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| pubmed:month |
Sep
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| pubmed:issn |
1520-5827
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| pubmed:author | |
| pubmed:issnType |
Electronic
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| pubmed:day |
21
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| pubmed:volume |
26
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| pubmed:owner |
NLM
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| pubmed:authorsComplete |
Y
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| pubmed:pagination |
14723-9
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| pubmed:meshHeading |
pubmed-meshheading:20722430-1,2-Dipalmitoylphosphatidylcholine,
pubmed-meshheading:20722430-Diffusion,
pubmed-meshheading:20722430-Liposomes,
pubmed-meshheading:20722430-Liquid Crystals,
pubmed-meshheading:20722430-Phase Transition,
pubmed-meshheading:20722430-Spectrometry, Fluorescence,
pubmed-meshheading:20722430-Thermodynamics,
pubmed-meshheading:20722430-Transition Temperature,
pubmed-meshheading:20722430-alpha-Tocopherol
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| pubmed:year |
2010
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| pubmed:articleTitle |
Phase-dependent lateral diffusion of ?-tocopherol in DPPC liposomes monitored by fluorescence quenching.
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| pubmed:affiliation |
School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany.
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| pubmed:publicationType |
Journal Article
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