Dear Pietro,
I think the fact that Arcimboldo works in expanding from one or a few helices (excellent but highly incomplete model), but only when you have good resolution data (preferably near 2A or better, but more powerful as the resolution increases) tells you that the fraction can, in principle, be very low. But you really can't get rules that don't depend simultaneously on the resolution of the data and the quality of the model.
As an even more extreme example (unpublished work that we're finally writing up), when you have data to very high resolution (preferably better than 1A), you can use Phaser to place as little as two individual sulphur atoms and then use that starting point to expand to a complete structure, essentially by picking peaks in a weighted difference map.
Best wishes,
Randy
> On 30 Sep 2015, at 21:35, Pietro Roversi <[log in to unmask]> wrote:
>
> Dear all,
>
> I am looking in the literature for a review and/or a survey discussing the percentage of asymmetric unit initially placed by MR which then primed model building and refinement and ended with structure completion and full structure determination.
>
> I am well aware that the most sensible answer to this question is: IT DEPENDS (on quality of the initial model, NCS, solvent content, etc etc etc.)
>
> I guess I am thinking of an ideal case of a 1:1 AB complex in which we have no-NCS, an average solvent content, no experimental phases and say an AB complex of which we can place A very accurately by MR. What is the ratio of A:B size that will allow tracing of B based on initial MR phases for A?
>
> In absence of a survey, examples from one's or one's friends' research will be also welcome - provided the examples have been published and can be cited.
>
> Thanks
>
> Pietro
>
> Sent from my Desktop
>
> Dr. Pietro Roversi
> Oxford University Biochemistry Department - Glycobiology Division
> South Parks Road
> Oxford OX1 3QU England - UK
> Tel. 0044 1865 275339
------
Randy J. Read
Department of Haematology, University of Cambridge
Cambridge Institute for Medical Research Tel: + 44 1223 336500
Wellcome Trust/MRC Building Fax: + 44 1223 336827
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