A high-throughput colourimetric method for the determination of pH in crystallization screens.

The crystallization of proteins is dependent on the careful control of numerous parameters, one of these being pH. The pH of crystallization is generally reported as that of the buffer; however, the true pH has been found to be as many as four pH units away. Measurement of pH with a meter is time-consuming and requires the reformatting of the crystallization solution. To overcome this, a high-throughput method for pH determination of buffered solutions has been developed with results comparable to those of a pH meter.