peptide alpha amino group protection reagent?

[antonio at liverpool.ac.uk]

:-Peter wrote:
> 
> Hi,
> 
>  Non-chemist here... First time poster, long time lurker...
> 
> I have an extremely hydrophobic peptide, to which I would like to
> conjugate NHS-Digoxigenin (after an EDC reaction) to the COOH terminus.
> There are no glu or asp groups present, and no epsilon amino groups
> present.
> 
> Unfortunately, I neglected to have the alpha amino group  on the amino
> terminus blocked during or after synthesis.  This means the post-EDC
> peptide will have two reactive amines, which for my purposes is not a good
> thing.
> 
> Can anyone suggest a readily available, hydrophobic "blocker" I can use to
> inactivate the alpha amino group?  This modifier must be membrane
> permeable, and it would be even sweeter if a radiolabelled  version were
> available too.
> 
> Thanks.
> 
> :-PeterIf you dont actually require the N terminal amine  you could just 
acetylate the peptide with acetic anhydride in say DCM, 15-30 min 
stirring at room temp at a 1.1 fold XS of acetic anhydride should work 
ok, though follow the reaction by RP-HPLC to confirm completion.

This would block the N-terminus very effectively and by use of acylases 
not necesarily irreversable.  I would of thought that a radiolabelled 
version of acetic anhydride would be available.

I hope this helps.

Len Bell.
lgbell at liv.ac.uk