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Updated: Feb 13, 2026

Structural Studies of Macromolecules in Solution using Small Angle X-Ray Scattering
Published on: November 5, 2018
A General Small-Angle X-ray Scattering-Based Screening Protocol Validated for Protein-RNA Interactions
Po-Chia Chen1, Pawel Masiewicz1, Vladimir Rybin1
1Structural and Computational Biology Unit , EMBL Heidelberg , Meyerhofstrasse 1 , 69126 Heidelberg , Germany.
Abstract:
We present a screening protocol utilizing small-angle X-ray scattering (SAXS) to obtain structural information on biomolecular interactions independent of prior knowledge, so as to complement affinity-based screening and provide leads for further exploration. This protocol categorizes ligand titrations by computing pairwise agreement between curves, and separately estimates affinities by quantifying complex formation as a departure from the linear sum properties of solution SAXS. The protocol is validated by sparse sequence search around the native poly uridine RNA motifs of the two-RRM domain Sex-lethal protein (Sxl). The screening of 35 RNA motifs between 4 to 10 nucleotides reveals a strong variation of resulting complexes, revealed to be preference-switching between 1:1 and 2:2 binding stoichiometries upon addition of structural modeling. Validation of select sequences in isothermal calorimetry and NMR titration retrieves domain-specific roles and function of a guanine anchor. These findings reinforce the suitability of SAXS as a complement in lead identification.
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