RE: [ccp4bb]: Data reduction for mosaic crystals....

["Frank Vondelft" <Frank.Vondelft@syrrx.com>]

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But if you have no choice (i.e. no more crystals, etc.) you should also
try D*trek.    I believe you can get a demo license to see if it does it
for you.

phx.



> -----Original Message-----
> From: Anastassis Perrakis [mailto:perrakis@nki.nl]
> Sent: Friday, June 07, 2002 7:56 AM
> To: Petri Kursula
> Cc: raji; ccp4bb@dl.ac.uk
> Subject: Re: [ccp4bb]: Data reduction for mosaic crystals....
> 
> 
> ***  For details on how to be removed from this list visit the  ***
> ***          CCP4 home page http://www.ccp4.ac.uk         ***
> 
> > Hi,
> >
> > Seems to me like a typical case where you should use XDS...
> >
> > Pete
> >
> 
> ..... well, it seems more like like a typical case of bad 
> data collection
> strategy ...  ;-)
> 
> > > Hi,
> > > I am working on a dataset where the crystal hasy a very 
> high mosaicity -
> > > my
> > > estimate is ~2.0 or more. Hence, I have had to take 0.1deg frames
> > > during data
> > > collection. Denzo V. 1.97.2 does not seem to be scaling 
> the data very
> > > well.
> 
> It is in general pointless to collect phi slices that are 
> less than half the
> mosaicity.
> 
> Why collect thin slices with high mosaicity ? Phine phi 
> slicing gets really
> powerfull with
> low mosaicity crystals only! Typically people reduce the phi 
> rotation in
> order to avoid overlaps.
> But, reducing it significantly lower than the mosaicty is 
> pointless. ie. the
> reflections will be overlapping
> simply because they do overlap since they are much too 'wide' 
> ... Thus, fine
> slicing will not help
> olving the problem and it will add very little to data 
> quality when mosaicity
> is high.
> 
> The best choice is to grow slightly different crystals, 
> freeze them better,
> or NOT freeze them
> (people tend to forget that you can actually solve a structure without
> cryo-freezing ...)
> 
> Steve Gamblin and Co had once good luck with VERY mosaic 
> crystals in the
> microfocus (>2.5), shooting just the edge
> of the pillow-like crystal and I am told that this was the 
> only thing that
> worked for them. But try the simpler things first.
> 
>     Tassos
> 
> --
> NKI, Department of Molecular Carcinogenesis
> Plesmanlaan 121 1066 CX Amsterdam NL
> Phone +31-20-512-1951 Fax +31-20-512-1954
> SMS: +31-6-28597791 WWW: http://den.nki.nl
> 
> 
>


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