From: Arthur Rowe IMAP <arthur.rowe@nottingham.ac.uk>
  To  : Andrew Leech <A.Leech@uea.ac.uk>
  Date: Tue, 21 Aug 2001 14:11:31 +0000

Re: [RASMB] Effect of isotopes (15N, 13C) on v-bar?

Andrew -

Your approach will probably give you a pretty decent approximation to the
vbar of your isotopic species, I think.

Consider what would be the toughest test of such an approach - namely,
estimating the density of deuterium oxide. The mass of the duuteron is twice
that of a proton, so a prediction would be approximately = (18+2)/18 = 1.11.
Not bad at all. If it works for deuterium oxide (where there are significant
effects of the extra nuclear mass on the chemistry and associative
properties of the species) then I think it should be OK for 13C and 15N.

All best

Arthur
--
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Arthur J Rowe
Professor of Biomolecular Technology
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> From: Andrew Leech <A.Leech@uea.ac.uk>
> Date: Thu, 16 Aug 2001 15:13:23 +0100 (BST)
> To: rasmb@alpha.bbri.org
> Cc: Andrew Leech <b078@uea.ac.uk>
> Subject: [RASMB] Effect of isotopes (15N, 13C) on v-bar?
> 
> 
> Hello everybody,
> 
> To calculate v-bar for a protein that has been isotopically
> labelled, can one simply correct the v-bar calculated by SEDNTERP
> by the ratio of the labelled/unlabelled masses, e.g.
> 
> normal v-bar 0.7138
> 
> normal mass 13187.9; 13C15N mass 13916.2
> 
> Hence 13C15N v-bar = 0.7138 x ( 13187.9/13916.2 ) = 0.6764
> 
> ... or have I made some dubious over-simplification here?
> 
> Thanks for any advice,
> 
> Andrew
> 
> ===================================================================
> 
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> Senior Research Assistant        *Fax +44 (0) 1603 592250
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> 
>