i was just refering to the mentioned "ideal case" with 43 se and 1300
aa in AU, and some real (successful) examples of same size range.
-tommi
Quoting "Bernhard Rupp" <[log in to unmask]>:
> What is not true?
>
> Also in your case the applet estimates an expected
> 4-5% signal which is quite doable with decent data.
>
> BR
>
> -----Original Message-----
> From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Tommi
> Kajander
> Sent: Friday, March 20, 2009 3:43 PM
> To: [log in to unmask]
> Subject: Re: [ccp4bb] Problems with phasing a protein (1300aa)
>
> this cant be true,
> in the idea case (not Rmerge 15%, then again one can apply a resolution
> cutoff, perhaps, while this sounds like a very desperate case) the
> answer must be yes. didnt do the calculation right now (but it
> _should_ back this up)
> we for instance have solved a structure long time ago
> -- and this probably wasnt on the limit (well it was at the time but
> not anymore), 365 res x 8 in AU and 80 Se.
>
> at least looking at the SnB success list ("very" old list )
> http://www.hwi.buffalo.edu/SnB/SnBSuccesses.htm
> there are plenty of others.
>
> -tommi
>
> On Mar 20, 2009, at 10:53 PM, Bernhard Rupp wrote:
>
>> One can estimate this from
>>
>> http://www.ruppweb.org/new_comp/anomalous_scattering.htm
>>
>> and the answer as Jim says is no.
>>
>> BR
>> -----Original Message-----
>> From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf
>> Of Jim
>> Pflugrath
>> Sent: Friday, March 20, 2009 1:08 PM
>> To: [log in to unmask]
>> Subject: Re: [ccp4bb] Problems with phasing a protein (1300aa)
>>
>> Well, what do you expect the anomalous signal contributed from your 45
>> seleniums in a perfect world to be when the asymmetric unit contains
>> 1300
>> aa? Do you think a dataset with Rmerge of ~15% is good enough to
>> detect a
>> signal of even 2%? (Note: I did not do the calculation, so I just
>> made up
>> the number of 2%.)
>>
>> Jim
>>
>>
>> On Fri, 20 Mar 2009, Kumar wrote:
>>
>>> Hello CCP4bb members,
>>>
>>> I have been trying to obtain phases for a protein which contain
>>> ~1300aa.
>> We
>>> have obtained native data to a resolution of 3.3A (Space group I222
>>> or
>>> I212121). But we are having tough time phasing it.
>>> ...
>>
>
> Tommi Kajander, Ph.D.
> Structural Biology and Biophysics
> Institute of Biotechnology
> University of Helsinki
> Viikinkaari 1
> (P.O. Box 65)
> 00014 Helsinki
> Finland
> p. +358-9-19158903
> [log in to unmask]
>
>
>
>
--
Tommi Kajander, Ph.D.
Macromolecular X-ray Crystallography
Research Program in Structural Biology and Biophysics
Institute of Biotechnology
P.O. Box 65 (Street address: Viikinkaari 1, 4th floor)
University of Helsinki
FIN-00014 Helsinki, Finland
Tel. +358-9-191 58903
Fax +358-9-191 59940
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