Synthesis, location, and lateral mobility of fluorescently labeled ubiquinone 10 in mitochondrial and artificial membranes

Krishna Rajarathnam, J. Hochman, M. Schindler, S. Ferguson-Miller

Research output: Contribution to journalArticle

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Abstract

To explore the influence of the long isoprene chain of ubiquinone 10 (UQ) on the mobility of the molecule in a phospholipid bilayer, we have synthesized a fluorescent derivative of the head-group moiety of UQ and measured its lateral diffusion in inner membranes of giant mitochondria and in large unilamellar vesicles. The diffusion coefficients, determined by the technique of fluorescence redistribution after photobleaching, were 3.1 × 10-9 cm2 s-1 in mitochondria and 1.1 × 10-8 cm2 s-1 in vesicles. Similar diffusion rates were observed for fluorescently labeled phosphatidylethanolamine (PE) with the same moiety attached to its head group (4-nitro-2,1,3-benzooxadiazole: NBD). Fluorescence emission studies carried out in organic solvents of different dielectric constants, and in vesicles and mitochondrial membranes, indicate that NBDUQ is located in a more hydrophobic environment than NBDPE or the starting material IANBD (4-[N-[(iodoacetoxy)ethyl]-N-methylamino]-7-nitro-2,1,3-benzoxadiazole). Fluorescence quenching studies carried out with CuSO4, a water-soluble quenching agent, also indicate that NBDUQ is located deeper in the membrane than NBDPE. These results suggest that ubiquinone and PE are oriented differently in a membrane, even though their diffusion rates are similar. Conclusions regarding whether or not diffusion of UQ is a rate-limiting step in electron transfer must await a more detailed knowledge of the structural organization and properties of the electron transfer components.

Original languageEnglish (US)
Pages (from-to)3168-3176
Number of pages9
JournalBiochemistry
Volume28
Issue number8
StatePublished - 1989
Externally publishedYes

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Artificial Membranes
Mitochondrial Membranes
Membranes
Mitochondria
Fluorescence
Quenching
Electrons
Photobleaching
Unilamellar Liposomes
Ubiquinone
Organic solvents
Phospholipids
Permittivity
Ubiquinone Q2
Derivatives
Molecules
Water

ASJC Scopus subject areas

  • Biochemistry

Cite this

Synthesis, location, and lateral mobility of fluorescently labeled ubiquinone 10 in mitochondrial and artificial membranes. / Rajarathnam, Krishna; Hochman, J.; Schindler, M.; Ferguson-Miller, S.

In: Biochemistry, Vol. 28, No. 8, 1989, p. 3168-3176.

Research output: Contribution to journalArticle

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