X rays from a free-electron laser resolve the structures of complex biomolecules

X-ray crystallography is remarkably successful at yielding atomic-resolution structures of proteins and other biological molecules. But that success has relied on growing macroscopic crystals. The countless identical molecules arrayed in a crystal share a radiation dose orders of magnitude higher than any one of them could tolerate alone. Moreover, the interference of x rays elastically scattered from the molecules concentrates the scattering intensity in a set of Bragg peaks. The larger the crystal, the better the signal-to-noise ratio.