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Figure 7.
Figure 7 Effect of UV-induced radiation damage. Experimental
difference electron-density maps (F[obs-UV] - F[obs-noUV]) are
shown for insulin. Maps are contoured at ±5.0  ,
where is
the standard deviation of the electron-density difference (red,
negative; green, positive) and are overlaid on a model of
non-irradiated insulin. (a) Overall view of the protein for a 1
s exposure to 266 nm laser light (the same difference map
displayed at ±3.0 is
also featureless and shows only noise peaks). (b) The same view
of the protein for a 60 s exposure to 266 nm laser light (with
identical power density as in a). (c) Example of a damaged
disulfide bridge. Breakage of the CysA7-CysB7 bridge is clearly
visible, together with a significant displacement of the
main-chain carbonyl group of CysA7. The maps were calculated
using CCP4 (Collaborative Computational Project, Number 4,
1994[Collaborative Computational Project, Number 4 (1994). Acta
Cryst. D50, 760-763.]). This figure was drawn using BOBSCRIPT
(Esnouf, 1999[Esnouf, R. M. (1999). Acta Cryst. D55, 938-940.])
and RASTER3D (Merritt & Bacon, 1997[Merritt, E. A. & Bacon, D.
J. (1997). Methods Enzymol. 277, 505-524.]).
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