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Biological Sciences
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May 2006

Researchers develop improved protein affinity probe

Figure 1. CrAsH (left) is a tetracysteine-binding probe, which is insensitive to hydrophobic moieties, resulting in improved fluorescence properties. Full Image.

PNNL scientists have developed a multi-use affinity probe for proteins that has improved properties compared to the parent compound. The new probe, CrAsH, which stands for carboxy-FlAsH (CrAsH-EDT2), is a tetracysteine-binding probe used to identify and validate protein interaction networks. CrAsH is cell permeable and, upon association with a specific tag encoded into a protein of interest, becomes highly fluorescent, enabling researchers to track cellular location and binding interactions.

The parent compound, FlAsH (for Fluorescein Arsenical Helix binder) bound nonspecifically to "greasy" structures, such as membranes and hydrophobic pockets of proteins, and gave a large background signal that made it unusable for most cells. The new CrAsH probe has minimal sensitivity to such structures and is therefore useful for live-cell imaging.

The work was done by Haishi Cao, Baowei Chen, Tom Squier, and Uljana Mayer for the U.S. Department of Energy's Office of Biological and Environmental Research's Genomics: GTL program. The results appeared as an advance article in Chemical Communications, a publication of the Royal Society of Chemistry.


Cao H, B Chen, TC Squier, and MU Mayer. 2006. "CrAsH: a biarsenical multi-use affinity probe with low non-specific fluorescence." Chemical Communications 24:2601-2603 (DOI: 10.1039/b602699k).

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