1: Biochemistry  1981 Jul 21;20(15):4270-7 

Dynamic structure of biological membranes as probed by
1,6-diphenyl-1,3,5-hexatriene: a nanosecond fluorescence depolarization study.

Kinosita K Jr, Kataoka R, Kimura Y, Gotoh O, Ikegami A.

A fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene, was incorporated in four
different biological membranes, the purple membrane of Halobacterium halobium,
human erythrocyte membrane, rabbit sarcoplasmic reticulum membrane, and rat
liver mitochondrial membrane. Time-resolved fluorescence depolarization of the
probe suggested that the rotational Brownian motion of the probe in the
membranes was restricted in the angular range. The motion of the rod-shaped,
lipophilic probe molecule, expected to reflect closely the motion of neighboring
lipid hydrocarbon chains, was analyzed in terms of the wobbling-in-cone model in
which the major axis of the probe was assumed to wobble freely in a cone of
semiangle theta c with a wobbling diffusion constant Dw. At 35 degrees C, Dw in
the four membranes, in the above order, ranged between 0.048 and 0.15 ns-1 and
theta c between 31 and 53 degrees. From the rotational rate Dw, the viscosity
against the wobbling motion was calculated to be 0.9-0.3 P. When the temperature
was raised from 10 to 35 degrees C, Dw in all membranes increased approximately
3-fold, corresponding to activation energies of 7-8 kcal/mol, and theta c
increased by about 10 degrees, except for the purple membrane in which the
angular range remained narrow. The same characteristic temperature dependence
has been found in many model membrane systems that contain unsaturated
lecithins, suggesting an important role of unsaturated phospholipids in the
dynamic structure of the lipid hydrocarbon chain region of biological membranes
at physiological temperatures. Comparison with model systems suggests that
proteins and cholesterol act mainly as barriers that narrow the angular range.

PMID: 7284326 [PubMed - indexed for MEDLINE]