I have found that the use of "redundancy" vs "multiplicity" correlates
very well with the speaker's favorite processing software. The
Denzo/HKL program scalepack outputs "redundancy", whereas scala/aimless
and other more Europe-centric programs output "multiplicity".
At least it is not as bad as "intensity", which is so ambiguous as to be
almost useless as a word on its own.
-James Holton
MAD Scientist
On 6/24/2020 10:27 AM, Bernhard Rupp wrote:
> Oh, and some of us prefer the word 'multiplicity' ;-0
Hmmm…maybe not. ‘Multiplicity’ in crystallography is context
sensitive, and not uniquely defined. It can refer to
1. the position multiplicity (number of equivalent sites per unit
cell, aka Wyckoff-Multiplicity), the only (!) cif use of multiplicity
2. the multiplicity of the reflection, which means the superposition
of reflections with the same /d/ (mostly powder diffraction)
3. the multiplicity of observations, aka redundancy.
While (a) and (b) are clearly defined, (c) is an arbitrary
experimental number.
How from (a) real space symmetry follows (b) in reciprocal space
(including the epsilon zones, another ‘multiplicity’) is explained here
https://scripts.iucr.org/cgi-bin/paper?a14080
and also on page 306 in BMC.
Too much multiplicity might create duplicity…
Cheers, BR
Jon Cooper
On 23 Jun 2020 22:04, "Peat, Tom (Manufacturing, Parkville)"
<tom.p...@csiro.au <mailto:tom.p...@csiro.au>> wrote:
I would just like to point out that for those of us who have
worked too many times with P1 or P21 that even 360 degrees will
not give you 'super' anomalous differences.
I'm not a minimalist when it comes to data- redundancy is a good
thing to have.
cheers, tom
Tom Peat
Proteins Group
Biomedical Program, CSIRO
343 Royal Parade
Parkville, VIC, 3052
+613 9662 7304
+614 57 539 419
tom.p...@csiro.au <mailto:tom.p...@csiro.au>
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*From:*CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK
<mailto:CCP4BB@JISCMAIL.AC.UK>> on behalf of
00000c2488af9525-dmarc-requ...@jiscmail.ac.uk
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*Sent:* Wednesday, June 24, 2020 1:10 AM
*To:* CCP4BB@JISCMAIL.AC.UK <mailto:CCP4BB@JISCMAIL.AC.UK>
<CCP4BB@JISCMAIL.AC.UK <mailto:CCP4BB@JISCMAIL.AC.UK>>
*Subject:* Re: [ccp4bb] number of frames to get a full dataset?
Someone told me there is a cubic space group where you can get
away with something like 11 degrees of data. It would be
interesting if that's correct. These minimum ranges for data
collection rely on the crystal being pre-oriented, which is
unheard-of these days, although they can help if someone is
nagging you to get off the beam line or if your diffraction fades
quickly. Going for 180 degrees always makes sense for a
well-behaved crystal, or 360 degrees if you want super anomalous
differences. Hope this helps a bit.
Jon Cooper
On 23 Jun 2020 07:29, Andreas Förster
<andreas.foers...@dectris.com
<mailto:andreas.foers...@dectris.com>> wrote:
Hi Murpholino,
in my opinion (*), the question is neither number of frames
nor degrees. The only thing that matters to your crystal is
dose. How many photons does your crystal take before it
dies? Consequently, the question to ask is How best to use
photons. Some people have done exactly that.
https://doi.org/10.1107/S2059798319003528
All best.
Andreas
(*) Disclaimer: I benefit when you use PILATUS or EIGER - but
I want you to use them to your advantage.
On Tue, Jun 23, 2020 at 12:04 AM Murpholino Peligro
<murpholi...@gmail.com <mailto:murpholi...@gmail.com>> wrote:
Hi.
Quick question...
I have seen *somewhere* that to get a 'full dataset we
need to collect n frames':
at least 180 frames if symmetry is X
at least 90 frames if symmetry is Y
at least 45 frames if symmetry is Z
Can somebody point where is *somewhere*?
...also...
what other factors can change n... besides symmetry and
radiation damage?
Thanks
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