From: Arthur Rowe <Arthur.Rowe@nottingham.ac.uk>
  To  : RASMB@bbri.org
  Date: Tue, 9 Nov 1999 17:03:40 GMT0BST

cavities - more thoughts

Hi RASMBERs !

I share Karen Fleming's scepticism as regards the presence of a real, large, single 
cavity within a protein, as distinct from the summed-up total void made up of 
many small packing dicontinuities with which we are all familiar. The energetics 
of maintaining such a void sound dubious.  However, the original communication 
from Jacqui Matthews gave the existence of a cavity as basic data, and whilst I too 
am no crystallographer, I would have guessed that competent professionals in this 
field, who I presume did Jacqui's structure, could distinguish between the average 
electron density of (disordered) water and of a void. 

It is actually difficult to speculate much further without knowing a bit more about 
real numbers here.  How big is the cavity, and how big is the discrepancy in M, 
Jacqui ?   I mean,  the presence of loosely packed water (average density <1) within 
the 'cavity' would perhaps account for a modest discrepancy, but for a anything 
major, its either a real, hollow cavity or there is some other explanation altogether.

We can assume, of course, that this is NOT an oligomeric structure, can we ?!

Best wishes to all

Arthur
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Professor Arthur J Rowe
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