Schwartz T L
Biophys J. 1971 Jul;11(7):596-602. doi: 10.1016/S0006-3495(71)86238-0.
Derivations of the Ussing flux ratio equation have, until now, required the membrane to be both bounded by parallel planes and homogeneous, except in the transmembrane direction. These constraints have been necessary for the theoretical demonstration that the equation is independent of membrane parameters in the absence of carriers, coupling, solvent drag, or "single-file" diffusion. In a new derivation, the flux ratio equation is shown to be valid in this kind of diffusion regime without regard to the three-dimensional structure of the membrane. Thus the constraints on both membrane homogeneity and membrane geometry are shown to be unnecessary. The general use of this equation to differentiate between simple, uncoupled diffusion and other membrane transport phenomena is thus placed on a firmer base. However, as in earlier derivations, it is necessary that isopotential, isobaric, constant concentration surfaces exist sufficiently close to the membrane on both of its sides.
到目前为止，乌斯通量比率方程的推导要求膜除了在跨膜方向外，要由平行平面界定且性质均匀。对于该方程在不存在载体、耦联、溶剂拖曳或“单通道”扩散时与膜参数无关的理论证明而言，这些限制是必要的。在一个新的推导中，通量比率方程在这种扩散状态下被证明是有效的，而无需考虑膜的三维结构。因此，对膜均匀性和膜几何形状的限制被证明是不必要的。这样，该方程在区分简单、非耦联扩散和其他膜转运现象方面的普遍应用就有了更坚实的基础。然而，与早期的推导一样，有必要使等势、等压、恒定浓度面在膜两侧足够靠近膜的位置存在。
