STEP-BY-STEP CONTROL BY TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY OF A PEPTIDE-SYNTHESIS CARRIED OUT ON POLYMER BEADS

The use of time-of-flight secondary ion mass spectrometry (Tof-SIMS) f or the step-by-step control of a peptide synthesis on a solid support is illustrated. The positive secondary ions, issuing from energetic fr agmentation, are characteristic of the terminal groups of the step und er investigation. The negative secondary ions result from the cleavage of the benzyl ester link between the polymer support and the first am ino acid, and provide direct identification of the growing sequence. T of-SIMS offers this unique analytical possibility without any prelimin ary separation of the peptide from its support.