Stain Protocol for the Detection of N-Terminal Amino Groups During Solid-Phase Peptide Synthesis
Hiroyuki Konno describes a stain protocol for the detection of N-terminal amino groups.
Solid-phase peptide synthesis (SPPS) – pioneered by the 1984 Nobel Prize winner Robert Bruce Merrifield – is the method of choice for the preparation of polypeptides. This highly versatile technology is used worldwide for the manual as well as automated synthesis of a wide range of peptides. Despite its success, direct monitoring of reactions on resin is not as straightforward as for reactions in solution where samples can be easily collected and directly analyzed through a variety of analytical and spectroscopic methods, such TLC, HPLC and NMR. The Kaiser test – based on the reaction between primary amino groups and ninhydrin which develops an intense blue color – is destructive and can easily lead to false positives (for example when Fmoc protecting groups are labile to the pyridine contained in the test cocktail) or negatives (secondary amines such as proline give rise to a rather ambiguous redbrownish color). Besides, the Kaiser test is timeconsuming and the test cocktail contains highly toxic reagents such as KCN.
The group of Professor Hiroyuki Konno at Yamagata University (Japan) recently reported a new test protocol to detect Nterminal amino groups during FmocSPPS using a reversible and non-destructive reaction.