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The original email stated that the cut splits the molecule into 200 and 500 aa each. Those should be distinguishable on SDS-PAGE, and I guess this information was taken into account by those who suggested that test. And yes, mass spec from a crystal (or at least a few) _has_ been done, so I assume it _can_ be done. Cheers, Tim -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen GPG Key ID = A46BEE1A On Thu, 1 Dec 2005 [EMAIL PROTECTED] wrote: > *** For details on how to be removed from this list visit the *** > *** CCP4 home page http://www.ccp4.ac.uk *** > > > Apologies for continuing to top-post here... > > If the cleavage would only remove 28 amino acids from a 500 amino acid > chain, it could easily be missed by SDS-PAGE, although mass spec would > catch it. However, I don't think you can get enough sample from a > dissolved crystal to run mass spec. > > To the original poster: you need to describe the electron density break to > us in more detail, or better yet, direct us to some screenshots. What is > your resolution? How good is the electron density in the vicinity of the > break? Can you see the side chains of residues 28 and 29? A true peptide > bond cleavage will leave free amino and carboxy termini which will not fit > in the same space as a peptide bond - even at modest resolution, you should > be able to see that C-alpha #28 and C-alpha #29 are not the canonical 3.8 A > apart; at high resolution, you would hopefully see the extra oxygen of the > COOH terminus. > > - Matt
