Jump to main content
Jump to site search
PLANNED MAINTENANCE Close the message box

Scheduled maintenance work on Wednesday 21st October 2020 from 07:00 AM to 07:00 PM (BST).

During this time our website performance may be temporarily affected. We apologise for any inconvenience this might cause and thank you for your patience.

Volume 171, 2014
Previous Article Next Article

Signal to noise considerations for single crystal femtosecond time resolved crystallography of the Photoactive Yellow Protein

Author affiliations


Femtosecond time resolved pump–probe protein X-ray crystallography requires highly accurate measurements of the photoinduced structure factor amplitude differences. In the case of femtosecond photolysis of single P63 crystals of the Photoactive Yellow Protein, it is shown that photochemical dynamics place a considerable restraint on the achievable time resolution due to the requirement to stretch and add second order dispersion in order to generate threshold concentration levels in the interaction region. Here, we report on using a ‘quasi-cw’ approach to use the rotation method with monochromatic radiation and 2 eV bandwidth at 9.465 keV at the Linac Coherent Light Source operated in SASE mode. A source of significant Bragg reflection intensity noise is identified from the combination of mode structure and jitter with very small mosaic spread of the crystals and very low convergence of the XFEL source. The accuracy with which the three dimensional reflection is approximated by the ‘quasi-cw’ rotation method with the pulsed source is modelled from the experimentally collected X-ray pulse intensities together with the measured rocking curves. This model is extended to predict merging statistics for recently demonstrated self seeded mode generated pulse train with improved stability, in addition to extrapolating to single crystal experiments with increased mosaic spread. The results show that the noise level can be adequately modelled in this manner, indicating that the large intensity fluctuations dominate the merged signal-to-noise (I/σI) value. Furthermore, these results predict that using the self seeded mode together with more mosaic crystals, sufficient accuracy may be obtained in order to resolve typical photoinduced structure factor amplitude differences, as taken from representative synchrotron results.

Back to tab navigation

Article information

13 Feb 2014
02 Apr 2014
First published
09 Apr 2014

Faraday Discuss., 2014,171, 439-455
Article type
Author version available

Signal to noise considerations for single crystal femtosecond time resolved crystallography of the Photoactive Yellow Protein

J. J. van Thor, M. M. Warren, C. N. Lincoln, M. Chollet, H. T. Lemke, D. M. Fritz, M. Schmidt, J. Tenboer, Z. Ren, V. Srajer, K. Moffat and T. Graber, Faraday Discuss., 2014, 171, 439
DOI: 10.1039/C4FD00011K

Social activity

Search articles by author