Le 11 nov. 09 à 13:16, Matthias Zebisch a écrit :
> Dear bb!
>
> What is the optimal wavelength for Sulfur SAD phasing?
> Is it 1.9A or should one go below that to reduce absorption/damage.
>
> Also, would the same wavelength be appropriate to maximize anomalous
> scattering to position chlorides, calcium, sulfate in already phased
> structures?
>
> Thanks in advance,
>
> Matthias
>
Hi Matthias,
We collected a highly-redundant sulfur-SAD data set at 2.0 A
wavelength. We managed to solve the structure thanks to two of the
three sulfur atoms present in the protein, plus one chloride ion that
happened to be bound to it. Radiation damage was an issue, but only
after anomalous redundancy was higher than 30. With very, very high
redundancy it was not possible to solve the structure. Thus, in some
cases, it may be worth trying with less images.
Of course, as Fred said, the precission of the measurements is
extremely important for sulfur-SAD phasing.
Best,
-- Miguel
Architecture et Fonction des Macromolécules Biologiques (UMR6098)
CNRS, Universités d'Aix-Marseille I & II
Case 932, 163 Avenue de Luminy, 13288 Marseille cedex 9, France
Tel: +33(0) 491 82 55 93
Fax: +33(0) 491 26 67 20
e-mail: [log in to unmask]
Web: http://www.pangea.org/mol/spip.php?rubrique2
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