MRI: Acquisition of a Small-Angle X-Ray Scattering Instrument

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

This proposal seeks the acquisition of a state-of-the art small-angle X-ray scattering instrument. The configuration of this instrument, combining a rotating anode source with two independent cameras, has been carefully designed around a diverse user community whose interests include protein aggregation, polymer science, zeolite nucleation, DNA electrophoresis, and colloidal science. A rotating anode source was chosen due to its high beam intensity, facilitating analysis of samples that scatter weakly. The dual all-angle/wide-angle (SA/WA) camera is a robust unit ideally suited for a multi-user instrument. This camera employs a line source exposing a larger sample volume to the incident beam subsequently reducing the time needed for data acquisition. The dual SA/WA camera can be used to study Bragg diffraction for analyzing crystallinity in polymers and the Kratky optics will allow us to characterize domains up to approximately 1000 nm in size. The dedicated small-angle camera, though more specialized, gives us the capability of two-dimensional imaging for samples that scatter anisotropically (e.g. semicrystalline polymers) and a wide range of sample-to-detector distances (100-1000 mm), making it possible to observe a wide range of scattering angles on one camera. The instrument will be located in the Crystal and Molecular Structure Laboratory (CMSL) in the Chemistry Department and maintained by the Materials Characterization Facility (MCF). The MCF is supported by the Colleges of Science and Engineering and the Office of the Vice President for Research, and both the CMSL and MCF have a well-developed infrastructure for student training and instrument maintenance. The user community for this instrument is inherently multidisciplinary, including faculty from Chemical Engineering, Mechanical Engineering, Chemistry, Biology, Biochemistry and Biophysics, and Medical Biochemistry and Genetics. The common need of these investigators is to understand structural issues that cannot be probed with methods such as diffraction or spectroscopy. Specific problems that will be addressed with this instrument include: 1. mechanisms of zeolite nucleation and the formation of other complex inorganic systems made in the presence of organic molecules 2. studies of core-shell particles and polymer-coated particles in concentrated systems 3. aggregation behavior of proteins and synthetic biomaterials in solution 4. in-vitro studies of biological membrane assemblies and macromolecules 5. determination of pore structures in gels used for DNA electrophoresis 6. processing-property relationships of amorphous and semi-crystalline polymers 7. non-destructive analysis of metal particle formation in dendritic materials This instrument will positively impact Texas A&M at several levels. It will be a focal point of several research programs and will give others a new tool for their current research. The proposed instrument would likely be one of the best laboratory SAXS instruments in the United States, so it will also enhance our ability to recruit leading faculty in the areas of polymeric and colloidal science. Finally, this instrument will positively impact education in two ways. Given the multi-user nature of this instrument it will be heavily utilized in student training of both graduates and undergraduates, with approximately 35 students initially performing research with the instrument. Second, this instrument will be integrated into a course one of us is developing (D. F. Shantz). As there is currently not a SAXS instrument on campus, this instrument will fill a large void in the infrastructure at Texas A&M, with research and education benefiting.