<div dir="ltr">On Mon, May 12, 2014 at 8:54 AM, Tim Gruene <span dir="ltr"><<a href="mailto:tg@shelx.uni-ac.gwdg.de" target="_blank">tg@shelx.uni-ac.gwdg.de</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">I don't know the formula for HL by heart and I don't see the<br>
Miller-Indices, but couldn't centric reflections have all four HLs = 0<br>
if the two-fold ambiguity is resolved and those reflections have<br>
phi=0? I thought phi=0 corresponds to A=B=C=D=0.</blockquote><div><br></div><div>Based on my reading of the ccp4 wiki, this appears to be incorrect:</div><div><br></div><div><a href="http://ccp4wiki.org/~ccp4wiki/wiki/index.php?title=Hendrickson_Lattman_coefficients">http://ccp4wiki.org/~ccp4wiki/wiki/index.php?title=Hendrickson_Lattman_coefficients</a><br>
</div><div><br></div><div>C=D=0 would be consistent with the phase ambiguity being resolved, but if A=B=0 that would imply that the figure of merit is also zero. However, it turns out that the tutorial output I was looking at does have all centric HL coefficients equal to zero - but my understanding (possibly incorrect) was that the centric reflections can't be phased using SAD (which explains why the figure of merit for centrics is always really poor in the Phaser output). In any case, if the MTZ file contains only centric reflections that by itself is worrying, although I found some lovely examples of this in the PDB yesterday.</div>
<div><br></div><div>-Nat</div></div></div></div>