Polystyrene-Immobilized PEG Chains

Abstract

Poly(ethylene glycol) (or PEG) is very compatible with peptides and proteins. It is soluble in water and almost all organic solvents, with the exception of aliphatic hydrocarbons and ether. This polymer was shown to be a valuable support for peptide and nucleotide synthesis in homogeneous solution (liquid-phase method1–5) as an alternative to the solid-phase method of Merrifield.13 In general, PEG of molecular masses 3000–20,000 daltons are used in liquid-phase peptide synthesis. Even insoluble free peptides often are solubilized, if covalently linked to PEG. On the other hand, the conformation of the peptide bound to PEG is the same as the conformation of the free peptide in the same solvents. A synthetic cycle using the liquid-phase procedure is shown in Scheme 1. The couplings are carried out in homogeneous solution.