hydrophobic peptides

novick@immunex.com
Thu, 8 Jul 1999 11:59:55 -0700

I have a glycoprotein with a highly hydrophobic peptide backbone that remains
soluable when glycosylated. However, when I digest and deglycosylate,
the hydrophobic peptides precipitate from solution. By holding the solution in
guanidine, I am able to arrest any visible precipitation however, my recovery of
2 peptides is only 50%. These peptides have ~30% leucine or isoleucine residues.
Ugh. The remaining peptide peices are not very hydrophobic and are recovered
well. At present I am using a Jupiter C4 column with water/acetonitrile/tfa
mobile phase.

Are there any ideas about how to increase my recoveries for these 2 peptides? I
am guessing that they're lost in the tube but perhaps they are lost once they're
injected. Has anyone put guanidine in their mobile phase?

Thanks for your help.
Shawn Novick