I re-cleaved the peptide over the weekend (with TFA 97.5% and TIS 2.5%) for one hour and got an excellent result. Although the resulting peptide would not precipitate when poured directly into cold ether, after I roto-vapped (my old adviser who flip that I just used "roto-vap" as a verb) off the TFA etc., the peptide formed a large yield of crystals with excellent purity. It is amazing that we all still have our favourite cocktails and we all believe them to be the best. Just goes to show you that there is no true right or wrong in peptide synthesis!
cheers,
Jane
Jane A. Nagel MSc
Genetics Institute
Cambridge, MA
1 888 577 1500 x 8597
jnagel@genetics.com