小中大5. Write up and try to publish the first purification that gives any product.
There is a tendency for readers, especially inexperienced readers, to assume that a published purification is the result of many cycles of improvement and optimization, and represents the best way to purify the protein. This is very often not true. Many times, it is just a series of steps, often chosen arbitrarily that happens to result in some product. One should look very carefully at a purification to assess if it is a procedure that is worth trying to follow if one wants to purify some of the target protein. This is why a proper purification summary table is so valuable. If huge losses occur at a particular fractionation step, if the overall yield is very low, if the final purity is not high, or if similar fractionation steps are used several times, then perhaps the procedure should merely be used as a beginning point in designing a better, more effective purification.
试图复制已发表的纯化方案
对文献的读者来说,特别是那些纯化新手,倾向认为已经发表的纯化方案是多次改进和优化的结果,是纯化这种蛋白的最佳方案。不幸这常常是错的。很多时候,这一方案仅仅是一系列偶然选择的步骤组合,碰巧可以纯化出一些目标蛋白。如果你想纯化出同样的目标蛋白,那么你应该仔细地研究一下这个纯化方案,看看它是否值得去尝试。这也是为什么一个恰当的总结表是如此重要。如果在某个特定的纯化步骤有巨大的目标损失;如果最终产品的纯度不是足够高;如果相似的纯化步骤用了好几次,那么也许这个纯化方案只能作为一个起始点,用以设计一个更好更有效的纯化方案。
我也常说这些话,甚至更甚。我认为绝大多数关于蛋白质纯化的文献都不是你该去复制方案的,也很难、很难复制出来,体系的影响因素太多了。看纯化文献的精髓在于得到一个关于目标蛋白性质的描述,而这些性质在我们用computer work是得不到,或是补充的。细节不可复制,策略可以参考。另外,看文献非常重要的一点是得到目标蛋白的检测方法,干扰因素,可能是活性测定方法,也可能是纯度检测方法等。