Selective purification of synthetic proteins by the use of FMOC- and biotin-based reversible chromatographic probes

Purification of proteins synthesised by the solid-phase stepwise approach, using conventional chromatographic tactics is often difficult and results in poor yields. Purification through selective labelling of the target sequence with chromatographic probes when accompanied by an efficient capping protocol is an effective way to drastically improve both the quality and yields of these large, chemically synthesised polypeptides. Basically, the chromatographic probe consists of two parts, an ‘affinity’ group that significantly changes the properties of the peptide possessing it and a reversible linker through which the probe is attached to the peptide. Furthermore, the latter is stable under the conditions used to deprotect and cleave the peptide from the resin support. After separation of labelled sequences from terminated peptides using a suitable ‘affinity’ chromatographic method the label is selectively removed thus yielding the purified polypeptide. Several ‘chromatographic probes’ have been proposed throughout the years. Those based on the FMOC molecule and on the biotin/avidin interaction seem to be of more general applicability and are discussed here.