The other use for these ultra-small beams is to illuminate part of a
larger xtal to find the best diffracting (or leat mosaic) regions and/or to
raster out of the radiation damaged areas. This way even "large" xtals
can benefit from this.
Nukri should chime in on this point as well since GMCA-CAT is pioneering
this approach.
- Th
Nave, C (Colin) wrote:
Hi
Yes good data with a micron size beam but, in this case, the path length
was 20- 30 micron.
I presume one would like a complete data set rather than a single or a
few processable images. If the latter, then in principle anything is
possible provided background is minimised and a low dose approach is
taken - as for single particle cryo electron microscopy.
I presume how to do all this will be one of the issues to be discussed
at the workshop (which I am looking forward to).
Regards
Colin
-----Original Message-----
From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of
Sanishvili, Ruslan
Sent: 21 April 2009 22:21
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] How small is a microbeam?
Hi Jon,
You can indeed get data with 1 micron(ish) beam. See for example
http://journals.iucr.org/d/issues/2008/02/00/wd5082/index.html
Different question is whether there is any benefit in using micron size
beam. It is subject of much work and discussion (e.g.
http://www.nsls.bnl.gov/newsroom/events/workshops/2009/mx/)
Regards,
Nukri
Ruslan Sanishvili (Nukri), Ph.D.
GM/CA-CAT
Biosciences Division, ANL
9700 S. Cass Ave.
Argonne, IL 60439
Tel: (630)252-0665
Fax: (630)252-0667
rsanishv...@anl.gov
-----Original Message-----
From: Jon Wright [mailto:wri...@esrf.fr]
Sent: Tuesday, April 21, 2009 3:36 PM
To: Sanishvili, Ruslan
Cc: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] How small is a microbeam?
Sanishvili, Ruslan wrote:
.......... Reasons for discriminating
5-10 micron beams (minibeam) from ca 1 micron (microbeam) might have
been not so much their size but what it involved to achieve these
sizes.
Might I ask - do you really get data from 1 micron protein crystals? The
reduction in scattering power (==crystal volume) from 5x5x5 microns to
1x1x1 is 125 and so it seems to present a grand challenge. I had
understood there to be a more fundamental size limit, coming from
radiation damage, which is still several microns for typical proteins.
Do you suggest that ~1 micron sized crystals are no longer exclusively
in the domain of powder diffraction? Millions of crystals working
together to increase the signal does help a lot for such tiny ones :-)
Going back to the original question, with 'nano' instead of 'micro', the
FDA has defined [1] a "100 nm size-range limit of nanotechnology".
Name suggetions for 100nm - 999 nm are most welcome. Are they
"submicron"?
Cheers,
Jon
[1] http://www.fda.gov/nanotechnology/regulation.html
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