Enantiomorph determination using inverse reference-beam diffraction images

It is shown that enantiomorph structures of a noncentrosymmetric crystal ca n be determined, in the absence of anomalous diffraction signals, by measur ing two series of reference-beam oscillation diffraction patterns related b y an inverse-beam geometry. The corresponding intensities of the Friedel pa irs recorded on the two sets of images exhibit the characteristic three-bea m interference effects that provide the unambiguous phase information. The experimental arrangement and the data-analysis procedure are demonstrated t hrough an experimental example on tetragonal lysozyme.