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![[Figure 3]](yp3239fig3mag.jpg)
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Figure 3
Structures of salen ligand (a)–(c), biotin (d)–(f), and thiostrepton (g)–(i) determined from EBEC MicroED data collected with different incident electron beam fluences. For both salen ligand and biotin molecules, shown are ORTEP diagrams and 3D models with the Fo density map contoured at 2σ. Single crystals were exposed to a total fluence of 0.5 [2°/s rotation, 2 integrated frames/s, 0.01 e−/Å2/s flux density, parts (a), (d), and (g)], 3.33 [0.3°/s rotation, 0.3 integrated frames/s, 0.01 e−/Å2/s flux density, parts (b), (e), and (h)], and 2.25 e−/Å2 [2°/s rotation, 2 integrated frames/s, 0.045 e−/Å2/s flux density, parts (c), (f), and (i)]. H atoms were included in the refinement and are displayed in the ORTEP diagrams, but were excluded from ball-and-stick models for clarity. Atomic B factors were refined anisotropically when possible, as was permitted for the 3.33 e−/Å2 fluence trials on the salen ligand and biotin, and the 2.25 e−/Å2 fluence trial on the salen ligand. Likewise, higher fluence generally allowed for greater accuracy in bond lengths for these compounds. Structures of thiostrepton are drawn as green models with superimposed blue 2Fo–Fc maps contoured at 1.8σ. Each is determined from a single crystal to 2.0 Å [part (g)], 1.5 Å [part (h)], and 1.8 Å resolution [part (i)]. Beneath each is the same model (cyan) superimposed with a green Fo–Fc map at 3σ, calculated from rigid-body refinement of the measured data against a poly-alanine model of thiostrepton. The clearest definition for side chains in the electrostatic potential map, and likewise the most prominent Fo–Fc density in the poly-alanine trial, was achieved with the highest fluence, the 3.33 e−/Å2 condition. |
![[Figure 3]](yp3239fig3.jpg)
 | STRUCTURAL CHEMISTRY |
ISSN: 2053-2296
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