Chemical ligation is a set of techniques used for creating long peptide or protein chains. It is the second step of a convergent approach. First smaller peptides containing 30-50 amino acids are prepared by conventional chemical peptide synthesis. They are then completely deprotected. Chemical ligation is the technique of selectively coupling these peptides in aqueous solution. With several coupling steps, proteins of up to 200-300 amino acids can be produced. Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... In chemistry a convergent synthesis is a strategy that aims to improve the effeciency of multi-step chemical synthesis. ... Phenylalanine is one of the standard amino acids. ... It has been suggested that solid phase peptide synthesis be merged into this article or section. ... Phenylalanine is one of the standard amino acids. ...

Methods of chemical ligation

There are various techniques described in literature. All of them involve a first kinetically controlled coupling step. The intermediate rearranges to form the amide bond. Older techniques rely on the presence of cysteine. Methods using removable auxiliary groups overcome this limitation. The most important one is Staudinger ligation. Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ...

Prior thiol capture

Prior thiol capture was the first ligation process. It was developed in the 1980s. Through a disulfide bridge N-terminal cysteine is brought into proximity of the C-terminal amino acid of the other peptide. A disulfide bond (SS-bond), also called a disulfide bridge, is a strong covalent bond between two sulfhydryl groups. ... The N-terminal end refers to the extremity of a protein or polypeptide terminated by an amino acid with a free amine group (NH2). ... The C-terminal end refers to the extremity of a protein or polypeptide terminated by an amino acid with a free carboxyl group (COOH). ...

Native chemical ligation

Developed in the 1990s, native chemical ligation is a method commonly used. N-terminal cysteine reacts with a C-terminal thioester. Native chemical ligation is a technique for constructing a large peptide from two smaller peptides, a C-terminal thioester peptide and a N-terminal cysteine peptide. ... General structure of a thioester. ...

Expressed protein ligation

By exploiting naturally present inteins it is possible to prepare a recombinant C-terminal thioester. This removes the size restriction of the C-terminal thioester fragment. The recombinant thioester can be ligated to a synthetic peptide bearing an N-terminal cysteine. Native Chemical Ligations of this kind using recombinant C-terminal thioesters is known as Expressed protein ligation. An intein is a segment of a protein that is able to excise itself and rejoin the remaining portions (the exteins) with a peptide bond. ... Recombinant proteins are proteins that are produced by different genetically modified organisms following insertion of the relevant DNA into their genome. ... General structure of a thioester. ...

Acyl initiated capture

Acyl initiated capture is similar to native chemical ligation, except that peptide thioacid is brought into reaction with N-terminal bromo-alanine. The product is a peptide including cysteine.

Staudinger ligation

With Staudinger ligation, developed in 2000, peptide chains can be linked independently of the terminal amino acids. The method is based on the Staudinger reaction. The Staudinger ligation or Staudinger reaction or Staudinger reduction is a chemical reaction in which the combination of an azide with a phosphine or phosphite produces a phosphorimidate . Combined with the hydrolysis of the phosphorimidate, to produce a phosphine oxide and an amine, this reaction is a mild method of...

References

Nilsson BL, Soellner MB, Raines RT. 2005. Chemical Synthesis of Proteins. Annu. Rev. Biophys. Biomol. Struct. 34:91-118