What I know about Deutrium labelled internal standards is that D should not be present on exchangeable sites. I am not much of a chemistry person but What I understand by GLYCINE 2,2 D2 means both the Ds are on is on alpha carbon and that position of Carbon is not exchangable...is it? In Glycine D5 all the hydrogens are substituted by D...out of which D attached to amino terminal and carboxy terminal are exchangable in solution.
So my little knowledge says that Glycine 2,2 D2 should be better. but In all the published research papers I have seen that they have used Glycine D5.
Kindly clear my confusion.
Thanks in advance.
Most people purchase which ever isotopologue is less expensive! The glycine d5 (which typically is the cheapest) will yield a peak 2amu higher just as with glycine d2 since the other 3 deuterons will exchange away in the d5 isotopologue.
To my surprise Glycine d2 is the cheapest of the all other glycine isotopes still I see only Glycine d5 being used. and there is lot of difference between the price too. That was the main reason of my confusion.
Anyways, So that means I can go on with glycine d2. Thankyou!! :)
I agree that D2 is a better choice, since it has less effect on the pKa of the amine group and its ionization.
Go to the d2 which will ensure no exchange at all of the deuterium as opposed to the d5!
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