| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1271019 | Bioelectrochemistry | 2014 | 9 Pages |
•Protonophoric activity of alkylamino-NBD derivatives was found in lipid membranes.•NBD-based fluorescent uncouplers of oxidative phosphorylation were screened.•n-Octylamino-NBD proved to be an uncoupler in mitochondria.•Half-maximal uncoupling concentration of n-octylamino-NBD was 5 μM.•NBD-based uncouplers showed a bell-shaped dependence on the alkyl chain length.
The environmentally sensitive fluorescent probe 7-nitrobenz-2-oxa-1,3-diazole (NBD) is generally utilized to monitor dynamic properties of membrane lipids and proteins. Here we studied the behavior of a homologous series of 4-n-alkylamino-substituted NBD derivatives (NBD-Cn; n = 4, 6, 8, 9, 10, 12) in planar lipid bilayers, liposomes and isolated mitochondria. NBD-C10 induced proton conductivity in planar lipid membranes, while NBD-C4 was ineffective. The NBD-Cn compounds readily provoked proton permeability of neutral liposomes being less effective in negatively charged liposomes. NBD-Cn increased the respiration rate and reduced the membrane potential of isolated rat liver mitochondria. Remarkably, the bell-shaped dependence of the uncoupling activity of NBD-Cn on the alkyl chain length was found in mitochondria in contrast to the monotonous dependence in liposomes. The effect of NBD-Cn on the respiration correlated with that on proton permeability of the inner mitochondrial membrane, as measured by mitochondria swelling. Binding of NBD-Cn to mitochondria increased with n, as shown by fluorescence correlation spectroscopy. It was concluded that despite a pKa value of the amino group in NBD-Cn being about 10, i.e. far from the physiological pH range, the expected hindering of the uncoupling activity could be overcome by inserting the alkyl chain of a certain length.
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