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. Author manuscript; available in PMC: 2017 Jul 1.
Published in final edited form as: Wiley Interdiscip Rev RNA. 2016 Apr 12;7(4):512–526. doi: 10.1002/wrna.1349

Figure 6.

Figure 6

Probing the ion atmosphere around RNA using ASAXS. (A and B) Real part of the anomalous scattering factor f’ for Rb+ ions (A) and Sr2+ ions (B), respectively. The f’ values at the energies used in the multiple energy ASAXS experiment are circled in red. Measurements at five energies are used to extract the number of ions from Eqn. 7. As described in the text, measurements at only two energies are used to generate the anomalous difference signals that report the spatial distribution of ions around the macromolecule. (C and D) ASAXS difference signals, Ianom (q) ~ b(q), for 0.1 M Rb+ ions (C) and 0.01 M Sr2+ ions (D), respectively. The ASAXS signal is calibrated on an absolute scale using water as a standard.