Hi Mark, I attach a little plot based on a quick analysis of recent PDB entries (between Jan 04 and Nov 06, only Xray). This shows the number of waters (HOH residues) per ATOM record (i.e. mainly protein, RNA/DNA). If you want the number of waters per amino-acid residue, you could just multiply it by about 10?
Converted into a VERY ROUGH 'rule of thumb': 2.5 Angstroem = 0.5 water per residues 2.0 1.0 1.5 1.5 1.0 2.0 But note the large error bars (at higher resolution probably because I ignored alternate conformations and partially occupied waters): so you have to do your own decision also based on the data quality and maps yourself, I guess. And: this is what deposited structures tell us - it doesn't mean we have to follow this. Hope that helps Cheers Clemens On Thu, May 17, 2007 at 03:44:14AM -0400, mark michaels wrote: > Hello everyone, > > I would like to ask for any information on reasonable, preferably > quantitatively derived values for the approximate crystallographic > H2O to residue ratio versus resolution for protein structures ? > > Any references or studies would be ideal, but rules of thumb > would also help. If there are any studies with greater detail, > such as per residue type, I'd appreciate learning of them also. > > I'd specifically like this for cryo conditions since that would > influence the results and my analysis involves structures > determined under cryo conditions. > > Thanks for any help. > > m > > _________________________________________________________________ > Catch suspicious messages before you open them?with Windows Live Hotmail. > http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_protection_0507 > -- *************************************************************** * Clemens Vonrhein, Ph.D. vonrhein AT GlobalPhasing DOT com * * Global Phasing Ltd. * Sheraton House, Castle Park * Cambridge CB3 0AX, UK *-------------------------------------------------------------- * BUSTER Development Group (http://www.globalphasing.com) ***************************************************************
WatersPerAtom.pdf
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