X-ray micro-diffraction studies on biological samples at the BioCAT Beamline 18-ID at the Advanced Photon Source

Abstract

The small source sizes of third-generation synchrotron sources are ideal for the production of microbeams for diffraction studies of crystalline and noncrystalline materials. While several such facilities have been available around the world for some time now, few have been optimized for the handling of delicate soft-tissue specimens under cryogenic conditions. Here the development of a new X-ray micro-diffraction instrument at the Biophysics Collaborative Access Team beamline 18-ID at the Advanced Photon Source, and its use with newly developed cryo-diffraction techniques for soft-tissue studies, are described. The combination of the small beam sizes delivered by this instrument, the high delivered flux and successful cryo-freezing of rat-tail tendon has enabled us to record data to better than 4 Å resolution. The ability to quickly raster scan samples in the beam allows selection of ordered regions in fibrous samples for markedly improved data quality. Examples of results of experiments obtainable using this instrument are presented.

Molecular and ultrastructural studies of a fibrillar collagen from octocoral (Cnidaria)

“…XRD on dry collagen fibers from S. ehrenbergi was performed at the Biophysics Collaborative Access Team (BioCAT, ID18) and the Biology Center for Advanced Radiation Sources (BioCARS, ID14) at the Advanced Photon Source, Argonne National Laboratory, Chicago, IL, USA (Barrea et al, 2014). Similar diffraction data from native, hydrated rat tail tendon and lamprey notochord were obtained from previous studies (Orgel et al, 2000(Orgel et al, , 2006Antipova and Orgel, 2010) and from linked RCSB codes (3HR2 and/or 3HQV).…”

X-ray diffraction from nonuniformly stretched helical molecules

“…Nucleic acids, especially DNA, either naturally adopt or can be induced to form helical structures as well (Mahendrasingam et al, 1986;Franklin & Gosling, 1953). While such macromolecular assemblies are generally intractable to conventional crystallographic approaches, X-ray fiber diffraction can be the method of choice to extract structural information from such molecular assemblies that have been induced to form aligned sols or gels by flow or magnetic fields (Chandrasekaran & Stubbs, 2012;Stubbs, 1999) and also, in many cases, from in situ measurements of protein assemblies in tissue or even living organisms Barrea et al, 2014). All such systems are characterized by helical symmetry of varying complexity (Vainshtein, 1966;Fraser & MacRae, 1973).…”