Electro-optical measurements were performed on membrane fragments containing (Na+ + K+)-ATPase. Data showed that these disk-shaped membrane fragments have a permanent electric dipole moment. Taking into account the size distribution of the membranes determined by electron microscopy, the value of the dipole moment is (5.5 ± 0.5) × 10-23 C m for a membrane of 1 μm2 area. This value does not depend on the conformational state of the (Na+ + K+)-ATPase (E1 and E2), however, if an uncleavable ATP analogue is added to the enzyme a significant increase in the permanent dipole moment is observed. The polarizability of the membrane fragments is less than 10-29 F m2.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry