Ah. Found the paper: Kantardjieff & Rupp (2003) Prot. Sci. 12, 1865.
"Matthews coefficient probabilities: Improved estimates for unit cell
contents of proteins, DNA, and protein-nucleic acid complex crystals."
There is a nice figure showing that data from the PDB shows a clear
correlation between lower solvent content and increasing resolution.
This is what one would expect on physical principles, but I can't find
the paper I read that suggested that in practice the reverse correlation
can be true. I'm probably remembering incorrectly what Ed is referring to.
Cheers,
Roger Rowlett
Edward A. Berry wrote:
mjvanraaij wrote:
how about this for a general idea:
resolution is related to order in the crystals, more order = diffraction
to higher resolution
the order is determined by crystal contacts, stronger crystal contacts =
more order
more solvent means, on average, less close packing and less crystal
contacts
(of course, there are cases where only a few strong crystal contacts
make for a very highly ordered crystal diffracting to high resolution,
so there are quite a few exceptions of high solvent content being
compatible with high resolution diffraction)
or is this too simplistic?
(and widely known?)
Sounds very reasonable to me. One the positive side (and this may be what
Roger was thinking of), for a given amount of protein in the
asymmetric unit,
increased solvent content means a larger unit cell and finer sampling
of the
molecular transform, -> more reflections and thus a greater data/param
ratio
at a given resolution. Also solvent flattening becomes more powerful.
Ed
