On Thu, May 14, 2009 at 03:03:57PM -0400, Guangyu Zhu wrote: > Zn and Se have similar f' and f''. Why Zn seems have much better phasing > powder in practice? Is it just because Zn always binds tightly on protein > but Se might have higher b-factor?
Also: Met sidechains often adopt alternate conformations (that still occupy the same space). You can see that in any structure, not only Se-MET (but also S-Met). If these alternate conformations are distinct enough, one can obviously model the minor conformations as well (e.g. by checking the LLG maps from SHARP). But the HA detection often finds only the main position - or the user restricts the sites to the maximum expected one according to sequence. Not sure though if that has as big an effect on the Zn/Se difference as the tightness/B-factor argument. Clemens -- *************************************************************** * Clemens Vonrhein, Ph.D. vonrhein AT GlobalPhasing DOT com * * Global Phasing Ltd. * Sheraton House, Castle Park * Cambridge CB3 0AX, UK *-------------------------------------------------------------- * BUSTER Development Group (http://www.globalphasing.com) ***************************************************************
