Crystallographic MAP phasing strategies explored using ELETTRA sincrotroneMnK-edge data to 2.1 angstrom and use of CHESS establishes the diffractionresolution limit as 0.92 angstrom for the protein Mn, Ca concanavalin A

Multiwavelength anomalous dispersion (MAD) data have been collected from a single crystal of the protein concanavalin A so as to evaluate different co mbinations of wavelengths for crystallographic structure determination. Dat a were recorded to 2.1 Angstrom resolution on a flash frozen crystal at thr ee wavelengths about the Mn K-edge (1.8951 Angstrom, 1.8940 Angstrom, 1.800 Angstrom) using synchrotron radiation at ELETTRA's Sincrotrone Trieste 'XR D' beamline. This is one of the longest wavelength K-edge MAD studies under taken to date. Anomalous and dispersive Patterson maps are seen to be of hi gh quality and indicate a high occupancy for the manganese binding site. Th is is confirmed also in the MAD phase determination and electron density ma ps. Finally 0.92 Angstrom data recorded at CHESS indicates the prospects av ailable for combined phasing strategies based on MAD to medium/high resolut ion along with ultra high resolution data.