41
Setting up a Synthesis
Cleavage
Various scavenger molecules are added to the TFA to prevent cleaved protecting groups from reattaching to the
peptide. The particular scavengers used depend on the specic peptide sequence. Common scavengers include
water (scavenges t-butyl cations), triisopropylsilane (TIS, scavenges trityl and Pbf cations), ethanedithiol (EDT,
scavenges t-butyl cations, reduces oxidation of Cys/Met side chains), dioxa-1,8-octane-dithiol (DODT, scavenges
t-butyl cations, suppresses oxidation of Cys/Met side chains), phenol (protects Tyr and Trp side chains from
oxidation), and thioanisole (aids in removal of Pbf protecting groups from Arg(Pbf), suppresses oxidation of Cys/
Met side chains).
Cleavage can be performed heated, or at room temperature. The table below lists CEM’s recommended
parameters for both heated and room temperature cleavages.
CEM Preference Cleavage Cocktail Temperature Time
1 TFA/TIS/H
2
O/DODT (92.5/2.5/2.5/2.5) 40-42°C 30 min
2 TFA/TIS/H
2
O/DODT (92.5/2.5/2.5/2.5) Room Temperature 3 h
NOTE
If the peptide contains multiple arginines, cleavage time may need to be extended to ensure complete Pbf
removal.
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