Re: [ccp4bb] Differentiating bound Mn Ca.

2007-04-16 Thread Julie Bouckaert
Hey David, You can do Mn2+ identification by its anomalous diffraction using the Cu Kalpha radiation. Mn is an anomalous scatterer at Cu Kalpha (1.5418 A), despite being distant from its absorption edge (somewhere around 1.96 A if I remember well). I did this for a double-manganese bound

Re: [ccp4bb] Differentiating bound Mn Ca.

2007-04-16 Thread Stephen Graham
Hi David, You can use Sheldrick's Calcium Bond Valence Sum to descriminate between metals (see Muller, P., Kopke, S., and Sheldrick, G. M. (2003) Acta Crystallogr., Sect. D: Biol. Crystallogr. 59, 32-37) even at low resolution. I have had good success with this method combined with estimation

Re: [ccp4bb] Differentiating bound Mn Ca.

2007-04-16 Thread Eleanor Dodson
In cases like this I use the S atoms to calibrate the peak height. Of course it isnt definitive a) it is near the noise level, and b) peak height is very dependent on B factor.. But the ratio might distinguish between an atom with an f of 1.3 or f=2.8 Eleanor David Briggs wrote: Dear all. I

Re: [ccp4bb] Differentiating bound Mn Ca.

2007-04-16 Thread Jim Pflugrath
Although the peak height of S atoms can be used as an internal yardstick, one has to worry about differences in occupancy and possibly hetergeneous sites (i.e. Ca, Mn and Mg) which can confuse the interpretation of the results. On Mon, 16 Apr 2007, Eleanor Dodson wrote: In cases like this I