Organic Solvent Nanofiltration: A New Paradigm in Peptide Synthesis

Abstract

Solid-phase synthesis is the dominant paradigm for peptide synthesis, used ubiquitously from discovery to production scale. However, the solid-phase approach produces coupling steps that may not be quantitative, introducing errors in amino acid sequences. It also entails an excess of reagents to overcome mass transfer limitations and restrictions on solvent, coupling chemistry, and protecting groups. Organic solvent nanofiltration (OSN) is a newly emerging technology capable of molecular separations in organic solvents. This contribution reports a new technology platform which advantageously combines OSN with solution-phase peptide synthesis, Membrane Enhanced Peptide Synthesis (MEPS). A first amino acid is linked to a soluble polyethylene glycol anchor. Through subsequent repeated coupling and deprotection steps, the peptide is extended to the desired length. The residual byproducts and excess reagents after each reaction are removed by diafiltration through a solvent-stable membrane which retains the peptide. Two pentapeptides are produced using this new technology. The purity of the peptides produced by MEPS is higher than that of peptides produced by solid-phase synthesis, under the same conditions. This illustrates clearly that MEPS benefits from the advantages of solution-phase synthesis, while avoiding the purification steps that have until now made solution-phase synthesis practically difficult.