Merkler I, Stournaras C, Faulstich H
Biochem Biophys Res Commun. 1987 May 29;145(1):46-51. doi: 10.1016/0006-291x(87)91285-x.
Discrepancies were observed when the polymerization of rabbit muscle actin was monitored by delta OD235 and viscometry (eta). For example, in the presence of (beta,gamma)-methyleno ATP, the delta OD signal was as large as with ATP although polymerization was very poor (eta 1.1, compared with eta = 1.7 in the presence of ATP). Furthermore, when monomeric actin, kept for 1 h in the presence of a stoichiometric equivalent of ADP, was exposed to conditions favoring polymerization (addition of MgCl2), a considerable delta OD235 signal appeared, although the actin had completely lost its polymerizability (eta = 1.0). We conclude that the observed changes in OD235 cannot reflect polymerization itself, but must be caused by another reaction preceding the assembly. Under normal conditions, this reaction is supposed to be the slowest step of filament formation and so to determine the velocity of the whole process. In conclusion, monitoring of actin polymerization by delta OD235 is a valid method only when polymerization has been assessed by another, independent method.
当通过ΔOD235和粘度测定法（η）监测兔肌肉肌动蛋白的聚合时，观察到了差异。例如，在存在（β，γ）-亚甲基ATP的情况下，尽管聚合非常差（η = 1.1，而在ATP存在下η = 1.7），但ΔOD信号与ATP存在时一样大。此外，当在化学计量当量的ADP存在下保存1小时的单体肌动蛋白暴露于有利于聚合的条件下（添加MgCl2）时，尽管肌动蛋白已经完全失去了其聚合能力（η = 1.0），但仍出现了相当大的ΔOD235信号。我们得出结论，观察到的OD235变化不能反映聚合本身，而必须由组装之前的另一个反应引起。在正常情况下，该反应被认为是细丝形成的最慢步骤，因此决定了整个过程的速度。总之，只有当通过另一种独立方法评估了聚合时，通过ΔOD235监测肌动蛋白聚合才是一种有效的方法。
