The map will be biased by whatever model is used to generate the phases.
If a heavy atom phasing method was used (MIR, MAD, etc) then at least you
do not have model bias.
A sigma-A weighted 2Fo-Fc map strives to have minimal bias, as does an
EDEN map with phase perturbation. However, minimally biased doesn't imply
negligible bias. A composite-omit 2Fo-Fc map made with simulated annealing
possibly comes the closest (apart from a heavy atom phased map).
HTH,
Bill
michael nelson wrote:
> In my understanding, unbiased electron density map usually refers to the
> Fo-Fc map.But I have seen in some papers sentences like that "The initial,
> unbiased 2FoFc map is contoured at".I was a bit confused since I was told
> by my instructor that the 2Fo-Fc was usually biased.
>
> Can anyone clear up this concept for me?
> Mike
>
>
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