Dear Alexandre,
The figure of 3 permil you mention for your 13C experiment is not to
dissimilar from what I've seen in tracer studies in humans when using a
tracer enrichment of 30MPE for a C1-labelled amino acid such as Phe (i.e.
30APE in the labelled position or 3.3APE overall for Phe) and a dose of
1mg/kg b.w..
If one assumes similar circumstances for the 2H experiment and a target
value of, say +50 permil vs. VSMOW for d2H of Phe (not taking into account
dilution by derivatisation) in muscle protein, the overall 2H enrichment of
the tracer would have to be only 0.772APE (or 6.95APE per labelled atom if
D2-Phe; or 2.78APE per labelled atom if D5-Phe), which is not surprising
given the low natural abundance of 2H.
The "problem" I foresee is the GC-IRMS analysis of ring-D5 Phe since this
will elute as a separate peak from the GC. The chromatographic isotope
effect will result in an as good as baseline separation of D5-Phe from
'natural' Phe. The peak as such may be nothing than a blip in the m/z 2
baseline but it will swamp the HD cup. A peak of pure
D5-Phe-N-acetyl,O-propylate would be 27.5APE in 2H!
I feel you'd be better off using D2-Phe since this should more or less
co-elute with the 'natural' Phe is you 'optimise' your GC conditions
accordingly.
Best regards,
Wolfram
> -----Original Message-----
> From: Stable Isotope Geochemistry
> [mailto:[log in to unmask]] On Behalf Of Alexandre Myre
> Sent: 01 November 2005 17:13
> To: [log in to unmask]
> Subject: Re: 2H content of amino acids in animals
>
>
> Cher Wolfram,
>
> Sorry for the delay, you are absolutely right, these are important
> factors I forgot to mention...
>
> The cows were bought from a farm near Quebec City. We have
> been feeding
> them with a mixture of 50 % corn sillage, 35 % grass sillage
> and 15 % of
> concentrated feed (moulee).
>
> They are drinking regular tap water which I did not analyse but it
> should be close to the tap water I have in the lab having a deuterium
> content of about -55 per mil VSMOW.
>
> We are planning on using ring-D5 PHE. I'm not sure of the level of
> enrichment we'll be aiming at... In our last experiment using
> 1-13C PHE,
> not enough tracer was injected and the isotopic enrichment in protein
> muscle was really small (3 per mil in th most). I guess that
> with more
> labelled atoms, it will be easier to enrich the muscle protein....
>
> We are analysing the bounded PHE of protein muscle with a GC-C-IRMS
> system and the free PHE of protein muscle with a GC-MS system.
>
> Thank you very much !
>
> Alexandre Myre
> Professionnel de recherche
> Departement des sciences animales
> Universite Laval
> Tel. 418-656-2131 ext. 11411
> Fax. 418-656-3766
> Pavillon Paul-Comtois
> Universite Laval
> G1K 7P4
> Ste-FOy, Quebec, Canada
>
>
> -----Original Message-----
> From: Dr W Meier-Augenstein <[log in to unmask]>
> To: [log in to unmask]
> Date: Sat, 22 Oct 2005 11:49:12 +0000
> Subject: Re: [ISOGEOCHEM] 2H content of amino acids in animals
>
> > Dear Alexandre,
> >
> >
> > I hope you won't mind "answering" your questions with more
> questions?
> >
> > (1) Where does your cattle live and where does their feed and water
> > come from? (2) What kind of 2H labelled Phe do you intend
> to use, e.g.
> > ring-D5
> > or chain-D2 and at what level of enrichment? (3) How are
> you planning
> > to
> > analyse your 2H-labelled Phe, IRMS or MS?
> >
> > A bientot,
> >
> > Wolfram
> >
> >
> > On Oct 21 2005, Alexandre Myre wrote:
> >
> > > > Hi everyone,>> we are considering a tracer experiment on steers
> > > > and cows using some 2H-> labelled phenylalanine tracer
> for muscle
> > protein
> > > > and plasma samples.>> I would like to know what type of isotopic
> > > > signature I can expect from> background values... I
> would also be
> > > > interested in amino acid 2H values> from other animals
> or human if
> > > > someone have some...>> Many thanks !>> Alexandre Myre>
> > Professionnel de
> > > > recherche> Departement des sciences animales> Universite Laval>
> > Tel.
> > > > 418-656-2131 ext. 11411> Fax. 418-656-3766> Pavillon
> Paul-Comtois>
> > > > Universite Laval> G1K 7P4> Ste-FOy, Quebec, Canada
>
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