Assembly of gap junction intercellular communication channels.

788 with a lipidlprotein molar ratio of 100:1, a value close to that found in most biological membranes [21]. The data show that the calculation of distances between sites within the monomer of a membrane protein of a cross-sectional diameter of 5 nm based only from FET efficiency measurements is largely speculative in most cases in native biological membranes. Because the contribution of FET to acceptors bound to neighbour protein monomers is highly dependent upon the lipid/protein molar ratio because of dilution of proteins in the lipid bilayer, reliable estimations of distances between functional sites in a protein monomer could a priori be obtained for any donor/acceptor pair with membrane proteins reconstituted with high lipid/protein molar ratios. In practice, however, the determination of the aggregation state of a protein in the membrane (native or reconstituted) is technically difficult, and the increase of light scattering of samples prevents one from working far beyond a lipidlprotein molar ratio of 1OOO:l. Therefore, the uncertainty in calculations of distances between functional sites in a protein monomer from measurements of FET efficiency remains high, unless the aggregation state of the membrane protein can be demonstrated to be monomeric in the samples used for fluorescence measurements.