Wieland D C F, Schroer M A, Gruzinov A Yu, Blanchet C E, Jeffries C M, Svergun D I
Institute for Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck Strasse 1, Geesthacht, 21502, Germany.
European Molecular Biology Laboratory, c/o DESY, Notkestrasse 85, Hamburg, 22607, Germany.
J Appl Crystallogr. 2021 May 25;54(Pt 3):830-838. doi: 10.1107/S1600576721003034. eCollection 2021 Jun 1.
Small-angle X-ray scattering is widely utilized to study biological macromol-ecules in solution. For samples containing specific ( metal) atoms, additional information can be obtained using anomalous scattering. Here, measuring samples at different energies close to the absorption edges of relevant elements provides specific structural details. However, anomalous small-angle X-ray scattering (ASAXS) applications to dilute macromolecular solutions are challenging owing to the overall low anomalous scattering effect. Here, pilot ASAXS experiments from dilute solutions of ferritin and cobalt-loaded apoferritin are reported. These samples were investigated near the resonance X-ray edges of Fe and Co, respectively, at the EMBL P12 bioSAXS beamline at PETRA III, DESY. Thanks to the high brilliance of the P12 beamline, ASAXS experiments are feasible on dilute protein solutions, allowing one to extract the Fe- or Co-specific anomalous dispersion terms from the ASAXS data. The data were subsequently used to determine the spatial distribution of either iron or cobalt atoms incorporated into the ferritin/apoferritin protein cages.
小角X射线散射被广泛用于研究溶液中的生物大分子。对于含有特定（金属）原子的样品，可以利用反常散射获得额外信息。在此，在接近相关元素吸收边的不同能量下测量样品可提供特定的结构细节。然而，由于整体反常散射效应较低，反常小角X射线散射（ASAXS）应用于稀大分子溶液具有挑战性。本文报道了来自铁蛋白和钴负载脱铁铁蛋白稀溶液的初步ASAXS实验。这些样品分别在德国电子同步加速器研究所（DESY）的佩特拉III的欧洲分子生物学实验室（EMBL）P12生物小角X射线散射光束线，在铁和钴的共振X射线边附近进行了研究。得益于P12光束线的高亮度，ASAXS实验对于稀蛋白质溶液是可行的，从而能够从ASAXS数据中提取铁或钴特异性反常色散项。随后，这些数据被用于确定掺入铁蛋白/脱铁铁蛋白蛋白笼中的铁或钴原子的空间分布。
