Chasan B, Solomon A K
Biochim Biophys Acta. 1985 Nov 21;821(1):56-62. doi: 10.1016/0005-2736(85)90152-x.
The reflection coefficient, sigma, is an irreversible thermodynamic parameter which measures the interaction between solute and solvent in passage across a membrane. The initial estimate of Goldstein and Solomon ((1960) J. Gen. Physiol. 44, 1-17) by the zero-time method gave sigma urea = 0.6 for the human red cell membrane and a more recent measurement by Levitt and Mlekoday ((1983) J. Gen. Physiol. 81, 239-253) using a different method gave sigma urea = 0.95. We have now developed a variant of the zero-time method which gives sigma urea = 0.70 +/- 0.02, which is significantly different from 1.0. There has been controversy as to whether urea permeates the human red cell by the same channel used by water or by a different route. The finding that sigma urea is significantly less than 1.0 (actually less than 0.95) makes it possible to discriminate between these two possibilities since completely independent transfer of urea and water mandates a value of sigma urea = 0.95. Values significantly lower than 0.95 can only be achieved if the transport of the solute, urea, is coupled to that of the solvent, water.
反射系数σ是一个不可逆的热力学参数，它衡量溶质和溶剂在跨膜转运过程中的相互作用。戈德斯坦和所罗门（（1960年）《普通生理学杂志》44卷，1 - 17页）通过零时间法初步估计人红细胞膜的σ尿素值为0.6，而莱维特和姆莱科代（（1983年）《普通生理学杂志》81卷，239 - 253页）使用不同方法进行的最新测量得出σ尿素值为0.95。我们现在开发了零时间法的一个变体，得出σ尿素 = 0.70 ± 0.02，这与1.0有显著差异。关于尿素是通过与水相同的通道还是通过不同途径渗透人红细胞，一直存在争议。σ尿素显著小于1.0（实际上小于0.95）这一发现使得能够区分这两种可能性，因为尿素和水完全独立转运时σ尿素值应为0.95。只有当溶质尿素的转运与溶剂水的转运耦合时，才能得到显著低于0.95的值。
