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1Y13: Difference between revisions
alternative explanation for cell changes
(alternative explanation for cell changes) |
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The almost-simultaneous DATEs in the headers may be explained by an inverse-beam measuring strategy which alternatingly collects 4 frames in one orientation as E1, then rotates the spindle by 180° and collects 4 frames into E2. For some reason, the beamline software did not write the correct wavelength into the headers. | The almost-simultaneous DATEs in the headers may be explained by an inverse-beam measuring strategy which alternatingly collects 4 frames in one orientation as E1, then rotates the spindle by 180° and collects 4 frames into E2. For some reason, the beamline software did not write the correct wavelength into the headers. | ||
So this little detective work appears to | Alternatively it may be the case that the crystal just changed its cell due to radiation damage during the 20-minute break - or that it even was exposed to the beam during that time, in an attempt of radiation-induced (papers by Ravelli ''et al''). | ||
So this little detective work appears to give us useful information about what happened in the morning of Sunday June 27, 2004 at ALS beamline 821 - but some questions remain. | |||
== Further analysis of datasets E1 and E2 == | == Further analysis of datasets E1 and E2 == | ||
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</pre> | </pre> | ||
At this point the structure is obviously solved, and we could use | At this point the structure is obviously solved, and we could use buccaneer or Arp/wArp to add side chains and the rest of the model. 3-fold NCS surely helps! | ||
== Could we do better? == | == Could we do better? == | ||
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* using a negative offset for STARTING_DOSE in XSCALE.INP, as documented in the [[XSCALE]] wiki article. | * using a negative offset for STARTING_DOSE in XSCALE.INP, as documented in the [[XSCALE]] wiki article. | ||
* use MERGE=TRUE in XDSCONV.INP. I tried it and this gives 20 solutions with CCall+CCweak > 25 out of 1000 trials, whereas MERGE=FALSE (the default) gives only 4 solutions! | * use MERGE=TRUE in XDSCONV.INP. I tried it and this gives 20 solutions with CCall+CCweak > 25 out of 1000 trials, whereas MERGE=FALSE (the default) gives only 4 solutions! | ||
* adding the "secondparts" data assuming this is a longer wavelength | * adding the "secondparts" data assuming this is a longer wavelength (but see above for an alternative explanation) | ||
But this time we learn that one has to take special care of the data in particular when they were measured by someone else who does not tell us everything we need to know. Second, zero-dose extrapolation made the day. | But this time we learn that one has to take special care of the data in particular when they were measured by someone else who does not tell us everything we need to know. Second, zero-dose extrapolation made the day. | ||