title: Squaric acid mediated chemoselective PEGylation of proteins: reactivity of single-step-activated α-amino poly(ethylene glycol)s.
abstract: The covalent attachment of poly(ethylene glycol) (PEG) to therapeutically active proteins (PEGylation) has become an important method to deal with the pharmacological difficulties of these polypeptides, such as short body-residence times and immunogenicity. However, the derivatives of PEG used for PEGylation lack further functional groups that would allow the addition of targeting or labeling moieties. Squaric acid diethyl ester was used for the chemoselective single-step activation of poly(ethylene glycol)s into the respective ester amides. The resultant selective protein-reactive poly(ethylene glycol)s were investigated with respect to their selectivity towards amino acid residues in bovine serum albumin (as a model protein). The presented procedure relies on a robust two-step protocol and was found to be selective towards lysine residues; the activated polyethers are efficient and stoichiometric PEGylation agents with a remarkable hydrolytic stability over a period of several days. By adjusting the pD value of the conjugation mixture, the chemoselectivity of the activated PEGs towards the α- and ε-amino groups of lysine methyl ester was effectively changed.
authors.affiliation: Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Dingels
authors.forename: Frederik
authors.initials: F
authors.lastname: Wurm
authors.forename: Manfred
authors.initials: M
authors.lastname: Wagner
authors.forename: Harm-Anton
authors.initials: HA
authors.lastname: Klok
authors.forename: Holger
authors.initials: H
authors.lastname: Frey
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D003503:Cyclobutanes / Q000737:chemistry*; D016503:Drug Delivery Systems; D004355:Drug Stability; D004591:Electrophoresis, Polyacrylamide Gel; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D011092:Polyethylene Glycols / Q000138:chemical synthesis / Q000737:chemistry*; D055550:Protein Stability; D011506:Proteins / Q000008:administration & dosage / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000596:Amino Acids; D003503:Cyclobutanes; D011506:Proteins; C482466:alpha-Amino-omega-hydroxyl-poly(ethylene glycol); D012710:Serum Albumin, Bovine; D011092:Polyethylene Glycols; C030042:squaric acid