IUCr journals

A magic triangle for experimental phasing of macromolecules

Acta Cryst. (2008). D64, 1179-1182 (doi.org/10.1107/S0907444908030266)

[Magic triangle] The magic triangle 5-amino-2,4,6-triiodoisophthalic acid (I3C) with three iodine atoms for anomalous scattering, arranged in an equilateral triangle (distances in Å), and three functional groups for hydrogen bonding.
Obtaining phase information for the solution of macromolecular structures is still one of the bottlenecks in X-ray crystallography. The compound 5-amino-2,4,6-triiodoisophthalic acid (I3C) is a representative of a novel class of compounds for heavy-atom derivatization that combines heavy atoms with functional groups for binding to proteins. I3C was incorporated into proteins in order to obtain phases by single-wavelength anomalous dispersion (SAD). An improved binding capability compared with simple heavy-metal ions, improved recognition of potential heavy-atom sites and low toxicity make I3C particularly suitable for experimental phasing.

T. Beck, A. Krasauskas, T. Gruene and G.M. Sheldrick