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LE10, LLE10, LE5, LE7, LD5 and homo E20 oligopeptides were prepared on a CEM Liberty peptide synthesizer. DMF and NMP were used as solvents and the standard CEM Liberty coupling protocols were followed. To achieve 1 mmol of oligomer, preloaded Wang resins containing glutamic acid (or aspartic acid for LD5) were used. The amino acid coupling was facilitated by use of Oxyma Pure/HBTU (0.5 M in DMF) and DIPEA (2 M in NMP).

Deprotection and release of the oligopeptides from the Wang resins was accomplished by 24 h treatment with a cleavage solution containing 95% TFA, 2.5% TIS (as a scavenger), and 2.5% H2O. The products were filtered and then precipitated in cold diethyl ether and centrifuged before lyophilization. The chemical purity of the oligopeptides was characterized by HPLC.