Dear all.
I have recently solved a structure in-house, 2.8A, CuKa.
I have a metal ion bound very obvious hepta-valent co-ordination, which
would suggest either Ca or Mn.
Neither was present in the crystallisation setup, but there was some Mg
around, which has contaminants of both Ca & Mn.
At 2.8A
David Briggs wrote:
Dear all.
I have recently solved a structure in-house, 2.8A, CuKa.
I have a metal ion bound very obvious hepta-valent co-ordination, which
would suggest either Ca or Mn.
Neither was present in the crystallisation setup, but there was some Mg
around, which has contaminants o
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 ConA,
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 of
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.
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
integrated values from both alternate
positions.
Regards,
Mitch
-Original Message-
From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Stephen Graham
Sent: Monday, April 16, 2007 2:23 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] Differentiating bound Mn & Ca.
Hi David,
Dave,
Others have given many excellent suggestions :) I'd like to mention that
to a protein biochemist such as myself, another obvious solution would be
to take an aliquot of the protein for a metal analysis (via ICP or AA).
ICP is more sensitive. Both Mn and Ca will light up the spectrum like new
Dear all.
Thanks to all of those who replied to my question, especially Clemens
Vonrhein, who patiently helped me get SHARP up and running...
Basically, there were 4 different ways suggested, with a few
embellishments here and there.
1) Use Dano peak height.
Taking the Dano peak height for intr
