NAP-taurine

More recently it has become clear that NAP-taurine passes through other membranes more readily than those of erythrocytes. It has proved difficult, for instance, to prevent its penetration into other types of mammalian cells. This limits its use for labeling membranes from the external medium. An even more important problem is that the molecule appears to bind to cell membranes like a detergent (Dockter, 1979 Richards and Brunner, 1980) and it seems that a number of the minor proteins labeled in intact erythrocytes penetrate the membrane deeply from the cytoplasmic side but do not span it. These proteins are accessible to NAP-taurine molecules that reach down into the hydrocarbon region of the bilayer. 

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