title: Understanding protease catalysed solid phase peptide synthesis.
abstract: A protease (thermolysin) was used to directly synthesise a number of dipeptides from soluble Fmoc-amino acids onto a solid support (PEGA1900) in bulk aqueous media, often in very good yields. This shift in equilibrium toward synthesis is remarkable because for soluble dipeptides in aqueous solution hydrolysis rather than synthesis is observed. Three possible reasons for the equilibrium shift were considered: (i) using a solid support makes it easy to use an excess of reagents, so mass action contributes towards synthesis; (ii) reduction in the unfavourable hydrophobic hydration of the Fmoc group within the solid support compared with the free amino acid in solution and (iii) suppression of the ionization of amino groups linked to the solid phase due to mutual electrostatic repulsion. It was found that under the conditions studied the second effect was most important.
authors.affiliation: Department of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, Scotland, UK EH9 3JJ.
authors.forename: Rein V
authors.initials: RV
authors.lastname: Ulijn
authors.forename: Nicola
authors.initials: N
authors.lastname: Bisek
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Halling
authors.forename: Sabine L
authors.initials: SL
authors.lastname: Flitsch
mesh_terms: D002384:Catalysis; D010450:Endopeptidases / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis*
chemical_list: D010455:Peptides; D010450:Endopeptidases