Recovering Fourier phase data from amplitude data alone in macromolecular X-ray crystallography

The ab initio phase problem is the rate-limiting step in X-ray crystallography and by extension is also a rate-limiting step in the determination of high-resolution 3-dimensional (3-D) structures of biological macromolecules. Thus it has dramatic repercussions for the emerging areas of rational drug-design and protein engineering. Simply stated, the problem is of recovering the real-space image of a biological macromolecule - represented in Cartesian 3-D coordinates-from partial Fourier information alone. Specifically, the available information in reciprocal space is that of the Fourier amplitudes; the complementary Fourier phase information is not available.