Contemporary methods for peptide and protein synthesis

This review describes current methods for peptide and protein syntheses, la rgely from a strategic point of view. The solid-phase method is useful for the rapid preparation of peptides. Two major synthetic strategies have been adopted by this method, namely, the Boc and Fmoc strategies. At the final stage of the Boc solid-phase method, a protected peptide resin is treated w ith a strong acid to obtain a free peptide. On the other hand, in the Fmoc solid-phase method, a free peptide is obtained by treating a protected pept ide resin with a weak acid. Both solid phase methods are quite useful for t he preparation of peptides with molecular weights in the vicinity of five t housand. Ligation methods were developed to overcome the molecular weight b arrier existing in a solid phase method. Building blocks used for ligation are prepared by the solid phase method, or more recently by biological meth ods. All the current ligation methods that produce a native peptide bond us e peptide C-terminal thiocarboxylic acids or thioesters as building blocks. Blake et al. developed a selective activation method of the C-terminal car bonyl group by the combination of thiocarboxylic acid and silver ions. Base d on this approach, a thioester method was developed, in which partially pr otected peptide thioesters are used as building blocks. Subsequently, a new ligation method was developed using peptide thioesters, in which protectin g group is no longer necessary. The discovery of protein splicing phenomeno n added a biological route to the preparation of peptide thioesters. A part ially protected peptides segment can be also derived from an expressed pept ide segment. Polypeptides with a molecular weight of more than 10 thousand can be routinely synthesized.