2.15. Purification of cyclic penta-peptides

Dissolve the crude peptide with purified water. Purification condition is shown as follows, load 3 mL of sample at flow rate of 1 mL/min using 0.1 % TFA + 100 % H₂O solution (buffer A) and 0.1 % TFA + 100 % acetonitrile (ACN) solution (buffer B) and equilibrate the preparative C18 column (Venusi MRC-ODS, 30 × 250 mm) at ratio of 90 % buffer A and 10 % buffer B for 5 min. The separation is performed under the gradient of 10 % buffer B to 80 % buffer B through 25 min. The purified solution is dried by lyophilisation to give the white-powder-form product. All peptides are greater than 95 % pure analyzed by HPLC.