In a message dated 98-03-25 16:14:32 EST, you write:
<< Subj: PEPTIDE SYNTHESIS
Date: 98-03-25 16:14:32 EST
From: stevens@chem.ucla.edu (richard stevens)
To: janyoung1@aol.com
Dear Jan, It's been such along time since I have talked to you.. How are
you doing? Are you still taking those long walks and reading novels for
reading clubs?
I have a techinical question for you. In Arv's research project on
cerebroside sulfate activator protein, Alan Waring has synthesized the
molecule(79 residues- very water soluble 3 disulfide bonds), and Kym has
looked at the mass spectrum by electrospray. About 1% has the correct mass
and there appear to be hundreds of other molecules ranging from 1 to 100
mass units off both + and -. This seems to be very strange. One might
expect that wrong molecules would be off by amino acid weights or blocking
group weights. Have others seen this with long sequenced peptides? Also
before it was looked at by electrospray much of it was precipitated on
dialysis. Its possible that interlinking disulfide bonds could be
responsible. To promote the correct disulfide linkages we would like to add
cerebroside sulfate to the synthesized mixture. The question is, when is
the best time to add this? in the cleaving process, the washing procedure
after cleavage or at a later time?
Alan synthesized the 79mer by FMOC on a PEG resin(low substitution)
on an ABI instrument.I believe he used trityl blocking groups on the CYS. He
cleaved for 90 min with a mixture of .25 ml EDT, .5 ml thioanisole, .5 ml
water, and 10 ml TFA. Is there a better way of cleaving? maybe HF?
Can you help us with our search for answers to these questions?
Maybe you could direct the questions to John Stewart or Gregg Fields or
anyone else that you know. Thanks for any help you may give.
Farzaneh and I are doing well and send our love.
Richard
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Dear Richard,
I really don't have an answer but I will forward your question. Are you on
the abrf list? Good to hear from you and especially since you are doing so
welllll. Love, Jan