4. Deblocking the carbonyl group of amino acid

The synthetic peptide purification is by compounds like water, anisol or thiol derivatives are added in excess during the deprotection step to react with any of

#### Figure 8.

Diagram of peptide cleavage after synthesis. The remaining N-terminal protecting groups, all side-chain protecting groups and the C-terminal protecting group or solid support are removed by strong acid treatment after peptide synthesis is completed.

Determination of Substrate Specificity of the Purified Novel Plant Cysteine Protease Solanain… DOI: http://dx.doi.org/10.5772/intechopen.90184

these free reactive species. This cycle of deprotection and coupling is repeated. The remaining protecting groups are cleaved by acidolysis, using; strong acids such as hydrogen fluoride (HF), hydrogen bromide (HBr) or trifluoromethane sulphonic acid (TFMSA) (Figure 8).
