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Figure 4
Online single-crystal UV–Vis spectroscopy showing the decaging of a coumarinyl photocage at 100 K in the absence of laser initiation, recorded on FIP(BM30A) at the ESRF. (a) UV–Vis spectra recorded from the same crystal, in the same orientation, before and after X-ray data collection show significant changes to the absorption spectrum of aspartate decarboxylase (ADC) crystals containing (coumarin-4-yl)-methyl-caged L-aspartate (inset) before (solid line) and after (dotted line) X-ray data collection. (b) Monitoring of the absorption of ADC containing (coumarin-4-yl)-methyl-caged L-aspartate at 350 nm during continuous X-ray exposure at 100 K (data shown in green with a fitted single exponential in blue) shows that photolysis is almost complete after a total absorbed dose of 80 kGy (RADDOSE-3D; Zeldin et al., 2013BB120). The contribution of the UV–Vis light source cannot be ruled out: no significant spectral changes were observed in the absence of X-radiation (B. A. Yorke, M. Sans Valls, J. I. Zaitseva-Kinneberg, D. Von Stetten and A. R. Pearson, personal communication).

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ISSN: 2059-7983
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