International
Tables for
Crystallography
Volume F
Crystallography of biological macromolecules
Edited by E. Arnold, D. M. Himmel and M. G. Rossmann

International Tables for Crystallography (2012). Vol. F, ch. 9.3, pp. 237-238

Section 9.3.4. Conclusions

D. Shapiroa*

aAdvanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, MS 2–400, Berkeley, CA 94720, USA
Correspondence e-mail: dashapiro@lbl.gov

9.3.4. Conclusions

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CXDM promises to be a highly efficient imaging methodology which can deliver high-resolution and high-contrast images of large non-crystalline biological structures. Radiation-induced shrinkage of dry cells will probably prohibit three-dimensional imaging of such cells at high resolution. However, significant three-dimensionality can be achieved through stereoscopic viewing of a cell, which only doubles the necessary X-ray dose. Even so, in the absence of low-dose diffraction techniques the sample must undergo considerable morphological change prior to imaging, although this change does not seem to alter the relative arrangement of organelles. The development of low-dose techniques will allow for the direct observation of these radiation-induced changes. In the long run, it is cryogenic protection that provides the most valuable structural information, since the cells are maintained in a near living state. Ultra-high-resolution three-dimensional imaging will still require the development of low-dose techniques, as cryoprotected samples have also been observed to suffer from mass loss with the accumulation of very high X-ray doses (>1010 Gy). These imaging techniques are currently under development at the ALS in collaboration with Stony Brook University and elsewhere. Alternatively, X-ray free-electron lasers (FELs) promise the highest resolution imaging of living cells that is possible by any means; indeed, it has been proposed that sub-nanometre resolution is possible (Bergh et al., 2008[link]). The ultra-short and ultra-bright pulses of an X-ray FEL will encode the structural information from a living cell before it is destroyed by the pulse.

References

Bergh, M., Huldt, G., Timneanu, N., Maia, F. R. & Hajdu, J. (2008). Feasibility of imaging living cells at subnanometer resolutions by ultrafast X-ray diffraction. Q. Rev. Biophys. 41, 181–204.
Lima, E., Wiegart, L., Pernot, P., Howells, M. R., Timmins, J., Zontone, F. & Madsen, A. (2009). Cryogenic X-ray diffraction microscopy for biological samples. Phys. Rev. Lett. 103, 198102.
Marchesini, S. (2007). A unified evaluation of iterative projection algorithms for phase retrieval. Rev. Sci. Instrum. 78, 011301.
Shapiro, D. A. (2004). Biological Imaging by Soft X-ray Diffraction Microscopy. PhD thesis, Stony Brook University.








































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