@JISCMAIL.AC.UK] On Behalf Of Jacob
Keller
Sent: Wednesday, 16 November, 2011 19:21
To: CCP4BB@JISCMAIL.AC.UK
Subject: [ccp4bb] Distinguish NH4 from Na?
Dear Crystallographers,
I have crystals containing 666mM NH4 and 540mM Na, and there appears
to be a water which is only about 2.2 Ang from some
Dear Jacob,
for NH4+, you would expect a (partial) tetrahedral coordination with
typical H-bond distances of ~2.9 A. For Na+, you would expect a
(partial) octahedral coordination with Metal-to-ligand distances of ~2.4
A (see Harding, Acta Cryst., D62, 678-682 (2006); Harding, Acta Cryst.,
Dear Crystallographers,
I have crystals containing 666mM NH4 and 540mM Na, and there appears
to be a water which is only about 2.2 Ang from some polar atoms. It
is currently reasonably happy as a Na, but is there any reasonable way
to decide which cation is there?
JPK
--
Bond valence sum
Muller et al. Acta Cryst. (2003). D59, 32-37 if the resolution is good (better
than 1.8 A)
R
On 16 Nov 2011, at 18:20, Jacob Keller wrote:
Dear Crystallographers,
I have crystals containing 666mM NH4 and 540mM Na, and there appears
to be a water which is only about 2.2
Dear JPK,
I think the coordination geometry of Na is a key, normally it adopts octahedral
geometry with Na---O distances of 2.1-2.2 ang, whereas water molecule is
h-bonded with H-acceptor or H-donor with the distances between 2.6-3.3 ang.
I am not sure it is correct, as i used to be
