IUCr journals

UV laser-excited fluorescence as a tool to visualize protein crystals mounted in loops

Acta Cryst. (2006). D62, 253–261 [doi: 10.1107/S0907444905041429]

[Protein crystal]Fluorescence images of a protein crystal (~20 μm long) under visible light (a) or UV light (b). Red points show the crystal centre as detected by automation software. The crystal is hardly detectable under visible light but easily identified under UV-laser illumination.
The automation of protein structure determination by crystallography encounters a serious bottleneck. Automated sample alignment along the synchrotron X-ray beam is often hampered by the difficult visualization of protein crystals. We have used the fluorescence from aromatic amino acids to identify reliably even tiny crystals. The use of a 266 nm UV laser in combination with an optimised illumination geometry and non-fluorescent sample holders provides an efficient solution to collect fluorescence images in milliseconds with standard camera optics. The low UV exposures do not generate detectable structural damage.

X. Vernede, B. Lavault, J. Ohana, D. Nurizzo, J. Joly, L. Jacquamet, F. Felisaz, F. Cipriani and D. Bourgeois