Tom:
The inosine is just another phosphoramidite, and its stability in ACN is
not eternal.
1) The argon is worse than helium for blanketing. Beckman Oligo 1000M
and Expedite 8909 obtained a much better record in amidite stability
than some ABIs mostly because they use Helium rather than Argon. The
reason: the Argon is more readily miscible with moisture. Even under
Helium the amidite stability is not longer than a couple of weeks in
general.
2) There are quite significant differences in stability (in ACN, HPLC
grade) between the various amidites. The deoxy inosine (dI) is a purine
and its stability is comparable to that of dG and dA, i.e. much lower
than the stability of, say, the Thymidine (T). The latter may be good
on the machines (or in capped bottles) for weeks and even longer. The
dG is the worst, we NEVER use G that has been for more than 4 days in
ACN. The dA and dI have the next worse stability (to my experience, but
I might well be wrong).
3) If you nevertheless MUST store the inosine in ACN for a prolonged
period of time, you may wish to keep it over molecular sieves. Still, I
would feel very uncomfortably storing it this way for more than a couple
of weeks and using it afterwards.
4) Your situation is in fact one of the most common ones - very often we
fulfill orders for one or two modified bases and we know that the next
similar order will come in a couple of weeks or even months. Only 0.1
ml was used by the machine, and there are still 0.9 ml left that will go
down the drain. And again, using 10% and throwing 90% away is not the
worst kind of waste we see around.
Best regards,
victor
www.alphadna.com
_____________________________
Thomas Miller wrote:
Hi all. I was wondering how stable inosine is in solution (dry
hplc grade acetonitrile)? Vial was blanketed with argon. Thank you.
Regards, Tom
*****************************************
Thomas Miller
DuPont Company
Protein Sequencing Lab and Oligo synthesis
email: Thomas.J.Miller@usa.dupont.com
phone: 302-695-1745
Opinions are my own and not of my employer
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