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JAMES E. HALL, RAMON
LATORRE
Biophys J. 1976
Jan;16(1):99-103
NONACTIN-K+ COMPLEX AS A PROBE FOR MEMBRANE
ASYMMETRY
From the Department of Physiology and Pharmacology,
Duke University, Durham,
North Carolina 27710. Dr. Latorre's present address
is the Department of Pharmacological and Physiological Sciences,
The University ofChicago, Chicago, Illinois 60637.
Since the introduction of artificial lipid bilayers
(Mueller et al., 1962), several molecules have been used as
probes of membrane structure. In particular, the nonactin-K+
complex has been used to probe membrane surface charge
(McLaughlin et al., 1970) and the shape of the electrochemical
barrier to transport inside the membrane (Hall et al., 1973).
More recently phospholipid bilayer membranes have been made with
negative lipids forming one monolayer and neutral lipids forming
the other (Montal, 1973). Such membranes are of considerable
interest because similar asymmetry may exist in biological
membranes (McLaughlin and Harary, 1974). The barrier shape for a
membrane with a neutral lipid on one side and a negative lipid
on the other should be skewed by the surface potential of the
negative lipid. We ask first if this is reflected in the
current-voltage curve. We find that the nonactin-K+
current-voltage curve shows a pronounced asymmetry in the
expected manner and consequently provides a direct measure of
the difference in the surface potential of a neutral and a
negatively charged lipid. We ask next how the observed membrane
asymmetry changes with time. |
