Editing Solid-phase synthesis (section)

==Solid-phase peptide synthesis (SPPS)==

Solid-phase synthesis is a common technique for [[peptide synthesis]]. Usually, peptides are synthesised from the [[carbonyl group]] side (C-terminus) to [[amino group]] side (N-terminus) of the [[amino acid]] chain in the SPPS method, although peptides are biologically synthesised in the opposite direction in cells. In peptide synthesis, an amino-protected amino acid is bound to a solid phase material or resin (most commonly, low cross-linked [[polystyrene]] beads), forming a [[covalent bond]] between the carbonyl group and the resin, most often an [[amido]] or an [[ester]] bond.<ref>{{Cite journal|last1=Guillier|first1=Fabrice|last2=Orain|first2=David|last3=Bradley|first3=Mark|date=2000|title=Linkers and Cleavage Strategies in Solid-Phase Organic Synthesis and Combinatorial Chemistry|journal=Chemical Reviews|language=en|volume=100|issue=6|pages=2091–2158|doi=10.1021/cr980040+|pmid=11749285|issn=0009-2665}}</ref> Then the amino group is deprotected and reacted with the carbonyl group of the next N-protected amino acid. The solid phase now bears a dipeptide. This cycle is repeated to form the desired peptide chain. After all reactions are complete, the synthesised peptide is cleaved from the bead.

The protecting groups for the amino groups mostly used in the peptide synthesis are 9-fluorenylmethyloxycarbonyl group ([[Fluorenylmethyloxycarbonyl protecting group|Fmoc]]) and t-butyloxycarbonyl ([[Tert-Butyloxycarbonyl protecting group|Boc]]). A number of amino acids bear functional groups in the side chain which must be protected specifically from reacting with the incoming N-protected amino acids. In contrast to Boc and Fmoc groups, these have to be stable over the course of peptide synthesis although they are also removed during the final deprotection of peptides.