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:[log in to unmask]] On Behalf Of
> Sanishvili, Ruslan
> Sent: 21 April 2009 22:21
> To: [log in to unmask]
> 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
> [log in to unmask]
>
> -----Original Message-----
> From: Jon Wright [mailto:[log in to unmask]]
> Sent: Tuesday, April 21, 2009 3:36 PM
> To: Sanishvili, Ruslan
> Cc: [log in to unmask]
> 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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