The use of neutron scattering is particularly suited for the analysis of protein-nucleic acid complexes and membranes because of the relatively large difference in neutron scattering between hydrogen and deuterium. This difference makes it easy to distinguish deuterium labeled proteins from unlabeled proteins, lipids and nucleic acids. In protein crystallography, neutrons reveal the presence of hydrogen and/or deuterium atoms with their intricate hydrogen bonding. Hydrogen-deuterium exchange studies provide information on dynamic properties of protein structures and provide detailed description of specific charge transfer mechanisms. The Brookhaven Neutron Scattering Facilities provides three automatic data acquisition systems with 2D detectors for protein crystallography, membrane diffraction and small angle scattering for the use of biologists through the U.S. The facility also provides technical and scientific staff for efficient running and maintenance of the facilities, as well as provision of "biological neutron" expertise for users unfamiliar with neutron scattering techniques.