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Figure 1
Determination of the oxygen saturation fraction of the crystals. (a) Ribbon diagram of OliHb. The A1, A2, B1 and B2 subunits are shown in red, green, yellow and blue, respectively. The A1 and B1 subunits form a dimer subassembly, and the A2 and B2 subunits form a similar dimer subassembly. Six A1B1 dimers and six A2B2 dimers form a spherical 24-mer assembly as a biological unit that is directly dissolved in the blood of the worm. (b) Crystal processing via ultraviolet laser. The image on the left is the crystal before processing, mounted in the cryo-stream. The image on the right is the crystal after processing. The values by the white lines are lengths in µm. (c, d) Reference absorption spectra of the oxy and deoxy forms obtained for OliHb in solution are shown as solid black lines. (e–h) The black circles are the absorptions measured from the processed crystals using a microspectrophotometer, and the orange lines are the fits calculated by a least-squares fit of the observed absorption spectrum to a linear combination of the oxy and deoxy reference spectra. The component reference spectra are shown as black dashed lines. Peaks around 630 nm are derived from the emission lines of the Hg–Xe lamp.

IUCrJ
Volume 8| Part 6| November 2021| Pages 954-962
ISSN: 2052-2525
https://doi.org/10.1107/S2052252521009386