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Frank von Delft wrote:
<blockquote cite="mid46A85D96.603@sgc.ox.ac.uk" type="cite">
<pre wrap="">
Jianghai Zhu wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Adding riding hydrogens into the structure was a powerful validation
tool. But now we all add riding hydrogens into the refinement since it
makes the refinement better. At the same time, we lose some power in
the validation. We still think it is worth doing so, don't we?
</pre>
</blockquote>
<pre wrap=""><!---->
No: they are RIDING hydrogens, they do not influence the refinement
(i.e. bumps), only the Rfactors/maps. Which is not the same as you ask
for with the phi/psi angles.</pre>
</blockquote>
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Not at all. Adding the hydrogen atoms from high to low resolution can
be viewed as adding additional anti-bumping restraints. The improvement
in the R/Rfree factors in this case is mostly attributed to overall
model geometry improvement and less attributed to adding additional
scattering power to the structure (depending on resolution). <br>
Saying differently, the X-ray gradients for H atoms are zero, H atoms
come to Fcalc and hence to X-ray target. However, the geometry
restraints target "sees" hydrogens as good as other atoms.<br>
<br>
Cheers,<br>
Pavel.<br>
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