A magic triangle for experimental phasing of macromolecules
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
![[Magic triangle]](https://www.iucr.org/__data/assets/image/0016/19150/ActaD2.tif.gif)
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.
