Can anomalous signal of sulfur become a tool for solving protein crystal structures?

A general method for solving the phase problem from native crystals of macr omolecules has long eluded structural biology. For well diffracting crystal s this goal can now be achieved, as is shown here, thanks to modern data co llection techniques and new statistical phasing algorithms. Using solely a native crystal of tetragonal hen egg-white lysozyme, a protein of 14 kDa mo lecular mass, it was possible to detect the positions of the ten sulfur and seven chlorine atoms from their anomalous signal, and proceed from there t o obtain an electron-density map of very high quality. (C) 1999 Academic Pr ess.