HIGH PERFORMANCE NEUTRON DETECTOR FOR PROTEIN CRYSTALLOGRAPHY

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DESCRIPTION (provided by applicant): Recently, with the increase in number of new neutron sources, stationary as well as portable, there has been growing utilization of neutrons in a similar manner. Contrary to X- and ?-rays, the probability of interaction of neutrons with matter does not depend on the atomic number but is rather irregular across the periodic table and depends on the nuclear structure of the absorber. Unlike X-rays, neutrons can easily penetrate many heavy elements, but are readily absorbed or scattered by various light isotopes, like hydrogen, deuterium, or lithium. Consequently, neutrons can provide information that would otherwise escape detection by conventional radiography. In biomedical and pharmaceutical research, neutrons are used in macromolecular crystallography to investigate the structure of molecules and proteins, which consist mostly of light elements. Neutron scattering experiments can resolve not only the atomic positions (elastic scattering) but also their dynamics (inelastic scattering). Due to the huge difference in scattering cross-section of hydrogen and deuterium, neutrons make it possible to resolve hydrogen exchange processes that are well beyond the capabilities of X-rays. While the benefits of neutron studies in biomedical sciences are obvious, the scope of such studies is limited at present by the available neutron detectors. The goal of the proposed project is to explore a new detector for neutron imaging studies based on a bright Gadolinium (Gd) compound. Advantage of Gd-based detectors is that this element has the highest cross-section for absorption of thermal neutrons. It means that only very thin layers of this material (200 microns or less) are required for nearly 100% absorption of thermal neutrons. This is important for three reasons. First, it improves utilization of the neutron beam. Second, it will provide better spatial resolution (less 1 mm) thus it will improve the resolving power of the instrumentation. Since the biological samples are usually on the order of millimeter in size it is important parameter. Third, thin layers will have small cross-section for gamma absorption, reducing gamma background and improving signal to noise ratio. The macromolecular (e.g. protein) structure strongly relates to its function and properties. Neutron crystallography can precisely pinpoint location of hydrogen atoms and help to define molecule's structure. Advancements in neutron detector instrumentation will provide better capabilities define these structures and help to recognize the molecule's purpose.