Laboratories of The Rockefeller Institute for Medical Research, Princeton, New Jersey.
J Gen Physiol. 1939 Nov 20;23(2):247-61. doi: 10.1085/jgp.23.2.247.
The following facts have been established experimentally. 1. In the presence of the synthetic detergent, Duponol PC, there is a definite reaction between dilute ferricyanide and denatured egg albumin. 0.001 mM of ferrocyanide is formed by the oxidation of 10 mg. of denatured egg albumin despite considerable variation in the time, temperature, and pH of the reaction and in the concentration of ferricyanide. 2. If the concentration of ferricyanide is sufficiently high, then the reaction between ferricyanide and denatured egg albumin in Duponol solution is indefinite. More ferrocyanide is formed the longer the time of reaction, the higher the temperature, the more alkaline the solution, and the higher the concentration of ferricyanide. 3. Denatured egg albumin which has been treated with formaldehyde or iodoacetamide, both of which abolish the SH groups of cysteine, does not reduce dilute ferricyanide in Duponol PC solution. 4. Cysteine is the only amino acid which is known to have a definite reaction with ferricyanide or which is known to react with dilute ferricyanide at all. The cysteine-free proteins which have been tried do not reduce dilute ferricyanide in Duponol PC solution. 5. Concentrated ferricyanide oxidizes cystine, tyrosine, and tryptophane and proteins which contain these amino acids but not cysteine. The reactions are indefinite, more ferrocyanide being formed, the higher the temperature and the concentration of ferricyanide. 6. The amount of ferrocyanide formed from denatured egg albumin and a given amount of ferricyanide is less in the absence than in the presence of Duponol PC. 7. The amount of ferrocyanide formed when denatured egg albumin reacts with ferricyanide in the absence of Duponol PC depends on the temperature and ferricyanide concentration throughout the whole range of ferricyanide concentrations, even in the low range of ferricyanide concentrations in which ferricyanide does not react with amino adds other than cysteine. The foregoing results have led to the following conclusions which, however, have not been definitely proven. 1. The definite reaction between denatured egg albumin in Duponol PC solution and dilute ferricyanide is a reaction with SH groups whereas the indefinite reactions with concentrated ferricyanide involve other groups. 2. The SH groups of denatured egg albumin in the absence of Duponol PC react with iodoacetamide and concentrated ferricyanide but they do not all react rapidly with dilute ferricyanide. 3. Duponol PC lowers the ferricyanide concentration at which the SH groups of denatured egg albumin react with ferricyanide. The SH groups of denatured egg albumin, however, are free and accessible even in the absence of Duponol PC.
以下事实已通过实验得到证实。
在合成洗涤剂 Duponol PC 的存在下，稀铁氰化物与变性卵清蛋白之间确实存在反应。氧化 10mg 变性卵清蛋白可形成 0.001mM 的亚铁氰化物，尽管反应的时间、温度、pH 值以及铁氰化物的浓度都有很大的变化。
如果铁氰化物的浓度足够高，那么 Duponol 溶液中，铁氰化物与变性卵清蛋白之间的反应是无限的。反应时间越长、温度越高、溶液越碱性、铁氰化物的浓度越高，形成的亚铁氰化物就越多。
用甲醛或碘乙酰胺处理的变性卵清蛋白，这两种物质都会使半胱氨酸的 SH 基团失活，在 Duponol PC 溶液中不能还原稀铁氰化物。
半胱氨酸是唯一已知与铁氰化物有确定反应或与稀铁氰化物反应的氨基酸。尝试过的不含半胱氨酸的蛋白质在 Duponol PC 溶液中不能还原稀铁氰化物。
浓铁氰化物氧化半胱氨酸、酪氨酸和色氨酸以及含有这些氨基酸但不含半胱氨酸的蛋白质。反应是无限的，形成的亚铁氰化物越多，温度和铁氰化物的浓度就越高。
在没有 Duponol PC 的情况下，变性卵清蛋白与给定量的铁氰化物反应形成的亚铁氰化物的量比有 Duponol PC 的情况下少。
在没有 Duponol PC 的情况下，变性卵清蛋白与铁氰化物反应形成的亚铁氰化物的量取决于温度和铁氰化物浓度，在整个铁氰化物浓度范围内都是如此，即使在铁氰化物浓度较低的范围内，铁氰化物也不会与除半胱氨酸以外的氨基酸发生反应。
上述结果得出以下结论，然而，这些结论尚未得到明确证明。
Duponol PC 溶液中变性卵清蛋白与稀铁氰化物的确定反应是与 SH 基团的反应，而与浓铁氰化物的不定反应则涉及其他基团。
没有 Duponol PC 的情况下，变性卵清蛋白的 SH 基团与碘乙酰胺和浓铁氰化物反应，但它们并非都与稀铁氰化物迅速反应。
Duponol PC 降低了变性卵清蛋白的 SH 基团与铁氰化物反应的铁氰化物浓度。然而，即使在没有 Duponol PC 的情况下，变性卵清蛋白的 SH 基团也是自由的且易于接近的。
