Microwave synthesis of prion protein fragments up to 111 amino acids in length generates biologically active peptides

Abstract

Misfolded conformers of the prion protein are aetiologically implicated in neurodegenerative conditions termed prion diseases (also known as transmissible spongiform encephalopathies). Two constitutively expressed N-terminal peptides corresponding to human residues 23–90 and 23–111 are thought to serve normal physiological roles related to neuronal protection with membrane binding possibly playing a part in their mechanism of action. These peptides, along with several derivatives up to 111 residues in length, have been produced by microwave assisted peptide synthesis. HPLC and MS characterisation showed that the peptides were manufactured in good yields at high purity. Peptides were assayed by fluorescence spectroscopy for synthetic lipid-membrane binding activity and by dichlorodihydrofluorescein diacetate assay for the amelioration of reactive oxygen species production. Results of these assays were similar to those reported for the wild type recombinant PrP, demonstrating that these synthetic peptides are useful for biological and chemical assays of PrP activity. Further, the longest peptide 1–111 was dimerised via a single internal cystine residue with good yield. The high yields and low purification burden of the microwave assisted synthesis method lends itself to the production of difficult to produce peptides for such studies.