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Distance Distribution between Two Iodine Atoms Derived from Small-Angle X‑ray Scattering Interferometry for Analyzing a Conformational Ensemble of Heavy Atom-Labeled Small Molecules

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posted on 25.06.2020, 20:34 by Yuya Taguchi, Tomohide Saio, Daisuke Kohda
To obtain unbiased information about the dynamic conformational ensemble of a molecule in solution, one promising approach is small-angle X-ray scattering (SAXS). Conventionally, SAXS data are converted to a pair distribution function, which describes the distance distribution between all pairs of atoms within a molecule. If two strong X-ray scatterers are introduced and the background contributions from the other atoms are suppressed, then the distance distribution between the two scatterers provides spatial information about a flexible molecule. Gold nanocrystals can provide such information for distances of >50 Å. Here, we synthesized a chemical compound containing two iodine atoms attached to the ends of a flexible polyethylene glycol chain and used the relevant singly labeled and unlabeled compounds to suppress the background contribution. This is a feasibility demonstration to prove that the distance distribution in the range of 10–30 Å can be experimentally accessed by SAXS.