Separations of hydrophobic synthetic peptides in counter-current chromatography.

Synthetic peptides with many aromatic, aliphatic and especially acidic amino acid residues are not very soluble and require strong solvents for useful partitioning. A chloroform-methanol-acidic solvent system fractionates neutral and basically charged 26-mers to provide high yields. An insoluble 15-mer with 5 Trp residues and 60% overall hydrophobic amino acid content was purified in pyridine-acetic acid and in another basic t-butyl methyl ether-n-butanol-acetonitrile solvent system with high recovery. Two instruments were used, the eccentric-multi-layer hybrid coil planet centrifuge and the new spiral disk planet centrifuge that were able to retain the stationary phase of these solvent systems, some of which have low interfacial tension.