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Hi Steve,
Jamie Cate used molecular replacement with EM maps to phase the ribosome at 18-9
angstroms. He described his technique (as applied to a 7.8A case) in
Cate JH, Construction of Low-Resolution X-ray Crystallographic Electron Density
Maps of the Ribosome, 2002, Methods 25(3):303-8.
Notably, he found that having accurately measured extremely low resolution
reflections (near the dimensions of the particle) was absolutely critical. In
one figure he compares a map from an 80-8A and a map from 300-8A. The former was
almost uninterpretable, due to ripples in the FT, while the latter looks fine.
Also, the pseudo-atom technique he uses with CNS may be obsolete, now that
Phaser can perform searches with maps.
Jacob
Q. Steven Xu wrote:
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Hi, everyone,
I am just wondering if anybody has experience on the molecular
replacement at very low resolution (say 20A or only 1000~2000
reflections). Was there any successful case at this resolution? or MR
has limitations on resolution (or the number of total reflections)? Any
reference?
Many thanks.
Steve Xu
LBL
--
Jacob Corn
The Berger Lab
UC Berkeley - Molecular and Cell Biology
[EMAIL PROTECTED]
phone: 510-643-8893
fax: 510-643-9290
