Biotechnology

Crystals on a Chip

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Science  03 Mar 2006:
Vol. 311, Issue 5765, pp. 1214
DOI: 10.1126/science.311.5765.1214c

Protein crystallization is a complex and often unpredictable process, which depends critically on buffer conditions and dehydration rates. Recently, microfluidic reactors have proven useful for screening a range of crystallization conditions with little material. However, these systems have rarely produced crystals large enough for analysis, nor has it been possible to preserve the crystals that do form for diffraction studies at cryogenic temperatures.

Hansen et al. have built a microfluidic device consisting of five parallel chambers, separated by a semipermeable membrane from a larger fluid reservoir. The osmotic strength of each chamber is equilibrated through internal diffusion among the chambers, as well as by a slow influx of vapor through the membrane. This motif can be repeated multiple times on a chip, with mixing times precisely controlled by modification of the channel lengths and chamber volumes. For lysozyme, ferritin, insulin, and catalase, they found that modulation of the mixing kinetics offered control over crystal quality, size, and even morphology. Moreover, crystals grown in these chambers could be preserved and studied in situ by x-ray diffraction to <2 Å resolution. — MSL

J. Am. Chem. Soc. 128, 10.1021/ja0576637 (2006).

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