SET-UP AND EXPERIMENTAL PARAMETERS OF THE PROTEIN CRYSTALLOGRAPHY BEAMLINE AT THE BRAZILIAN-NATIONAL-SYNCHROTRON-LABORATORY

The Brazilian National Synchrotron Light Laboratory (LNLS) has a dedic ated protein crystallography beamline. The optical elements of the bea mline include an elastically bent cylindrical mirror and a triangular bent-crystal monochromator, which focus synchrotron radiation at the p osition of the sample in the vertical and horizontal planes, respectiv ely. The monochromatic radiation is tunable between 2.0 and 1.2 Angstr om with the optimum wavelengths from 1.3 to 1.6 Angstrom, chosen to ma ximize the photon flux from the bending magnets of the storage ring (1 .37 GeV). Diffraction images are recorded on a 345 mm-diameter MarRese arch image-plate detector system with on-line readout. The experimenta l parameters of the beamline, such as the integral monochromatic flux and focus size, have been measured. The size of the beam at the positi on of the focal point is 0.5 x 0.5 mm(2). The flux density is between 4.4 x 10(10) and 8 x 10(10) photons s(-1) mm(-2) for wavelengths from 1.28 to 1.6 Angstrom. The energy resolution is sufficient to measure a bsorption edges of elements between 1.28 and 2 Angstrom. The facility, intended to serve the national and international community, has been commissioned and is available for users.