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BP: Fachverband Biologische Physik

BP 20: Protein Structure and Dynamics

BP 20.8: Vortrag

Mittwoch, 11. März 2026, 17:15–17:30, BAR/0106

ASAXS Based Absolute Intra-Molecular Distance Measurements for Proteins — •Samuel Stubhan¹, Anna Baptist¹, Caroline Körösy¹, Alessandra Narducci², Gustavo Gabriel Moya Munoz², Nicolas Wendler², Aidin Lak¹, Michael Sztucki³, Thorben Cordes², and Jan Lipfert¹ — ¹Department of Physics and Center for NanoScience, LMU Munich, Amalienstr. 54, 80799 Munich, Germany — ²Physical and Synthetic Biology, Faculty of Biology, LMU Munich, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany — ³ESRF, 71 Avenue des Martyrs, 38043 Grenoble, France

Intramolecular distance measurements are key to understanding macromolecular structure and dynamics. Anomalous Small-Angle X-ray Scattering (ASAXS) interferometry enables such measurements by attaching small (~1 nm) gold nanoparticles to target molecules and using X-ray scattering to extract distance distributions. ASAXS provides absolute distances over >10 nm, full ensemble distributions, and minimal sensitivity to label orientation, offering advantages over FRET and NMR.

We demonstrate ASAXS on proteins for the first time using two cysteine variants of maltose binding protein in apo and holo states, directly revealing ligand-induced conformational changes. The resulting distance distributions agree with single-molecule FRET measurements. Requiring only a double-labeled sample and accommodating diverse solution conditions, ASAXS offers a robust, broadly applicable tool for probing protein conformational ensembles.

Keywords: ASAXS; intramolecular distances; Maltose-Binding Protein; molecular ruler; gold NPs