Optimal chemistry for Rainin Symphony

mcada002@mc.duke.edu
Tue, 26 Jan 1999 10:54 -0500 (EST)



To: All using the Rainin Symphony Peptide Synthesizer

I have been using this instrument for about seven months now and am
over all very pleased with the ease at synthesizing multiple peptides
simultaneously.

However, I do have some peptides that do not synthsize well at all.
I am not in a position to spend time and dollars for R&D. Although, I
have done that to some extent. I would like to improve my
"success/failure" ratio.

Some difficulties I have noticed:

a. coupling phosphorylated amino acids - even with extended
coupling times.
b. peptides with multiple Prolines.
c. hydrophobic peptides.
d. ??? and some that I cannot see a known reason for the poor
quality.

I have found that using 0.1M HOBT/20% piperidine/NMP as deprotect
reagent does help with the Asp-X difficulties.

I have several years experience with the ABI peptide synthesizers
which use a bit different activator solution (HBTU/HOBT/NMP, catalyzed
with DIEA). I wonder if the activator used with the Symphony is as
robust as the one used on the ABI instruments. Is there an alternative
that has been proven more effective than the one I am currently using?

Currently, I am using:

Activator: 400mM NMM/150mM HBTU in NMP
Deprotectant: 0.1M HOBT/ 20% piperidine/ NMP
Amino acid concentration: 150mM (used 200mM routinely for a while,
and switched with no noticeable drop in quality.
Capping: 50% Acetic Anhydride/NMP


Coupling time: 40 minutes (2 x 30 min. for double coupling)
Deprotect time: 2 x 15 minutes
Capping time: 10 minutes

Resins: Usually loaded Chlorotrityl resins ( PAL for C-term amides)

I would appreciate some discussion on the different protocols you are
using with good success.

Thanks in advance!


Millie McAdams/ HHMI Biopolymer Facility @ DUMC
919-684-2652
FAX 919-684-5458
email: mcada002@mc.duke.edu