Figure 8.

Crystal size and homogeneity estimation using a Neubauer counting chamber. Xylose isomerase microcrystals are shown before and after optimization of the batch crystallization process for improved size homogeneity. Before optimization (a),(b) the sample shows high crystal size heterogeneity. While one of the strengths of the chip technology lies in its tolerance of variable crystal sizes, a homogeneous crystal size distribution is advantageous for both homogeneous reaction initiation in time-resolved experiments and for stability of scaling during data processing. (a) Overview of xylose isomerase microcrystals in a Neubauer cell-counting chamber (the scale bar is 500 µm). (b) Close-up view of the indicated area (the scale bar is 50 µm). (c) Xylose isomerase sample after optimization of the crystal size homogeneity (the scale bar is 100 µm). This crystal concentration (∼2.88 × 10⁶ ml⁻¹) should be diluted by a factor of two for TR-SSX experiments with the vacuum loading approach (described below), to avoid overloading the chip.