Hi Kai,
I assume these sites are not enough to resolve the enantiomorph
ambiguity witj SHELXE so that you obtain an interpretable map?
My suggestion is to user SHARP/AutoSHARP - go to
https://www.globalphasing.com/sharp/ register, download and install the
software - it runs via a web interface.
Best regards and good luck,
Pedro Matias
Às 12:40 de 11/07/2026, [email protected] escreveu:
Dear all,
I am currently processing a SAD dataset collected from a Se-Met
derivative. According to the |matthews_coef| calculation in CCP4,
there should be 20 heavy atom sites in the asymmetric unit.
However, due to the very weak anomalous signal, the occupancy
refinement in SHELX shows only one site with an occupancy above 1.0,
one site around 0.4, and the remaining 15 sites all converging to
approximately 0.3.
Given this situation, I would be very grateful for any suggestions on
how to obtain reliable initial phases. Are there any specific
strategies, software settings, or alternative approaches (e.g.,
density modification or partial structure refinement) that you would
recommend to make the most of this weak signal?
Thank you in advance for your time and insights.
Best regards,
Kai Zhang
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