However, do not get too excited if this resolution limit is 6 A. Although 6 A phases are better than no phases at all, have you ever LOOKED at a 6 A map? It can be very hard to tell if it is protein or not, even with perfect phases and all the right hand choices, etc.
If the map is a 6 Angstrom SeMet map you may well be right, since if the signal goes to 6 Angstrom the data at 7 Angstrom isn't that hot either. However if this was a Ta6Br12 6 Angstrom map then it can look quite pretty for the resolution because the 7 Angstrom SAD data in that case can be pretty good. Case in point it the one we collected for PP2a ABC holoenzyme cleared up all sorts of things about the partial molecular replacement solution, including some reassurance that the desperation WD40 ensemble MR solution was actually correct. At 6A, the WD40 looked somewhat like a Bagel (or a Bundt Cake if one is familiar) but the helices in one of the other subunits (A) were actually nicely resolved.
Excitement may be warranted, even at 6 Angstrom. Phil Jeffrey Princeton
