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
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