In simple terms, a synthetic peptide is a peptide bond formed between two amino acids; where a peptide refers to a flexible chain consisting of 30-50 amino acids. The process of synthesizing peptides is more than 100 years old; however, syntheses including "oxytocin" and "insulin" came later. The efficiency of synthetic chemistry has rapidly increased over the years, and today it is a common method in biological research centers. It is more commonly used for peptides in cosmetic and drug development.
The main advantage of synthetic peptides is that essential peptides found in biological samples can now be made in the laboratory. Furthermore, they can be optimized to produce the desired biological response by adding additional properties to the original peptides. It is usually done by coupling the carboxyl group of an amino acid to the N-terminus of a peptide chain (C-to-N synthesis). However, due to its complex nature, the coupling is controlled in strictly cyclic process steps.
Amino acids are added to the growing peptide chain, one at a time. They have many reactive groups; therefore, care must be taken to avoid any side reactions such as peptide chain length reduction and branching. Therefore, the research center developed chemical groups that bind to specific reactive blocks of amino acids and protect functional groups. Individual amino acids are reacted with protecting groups before synthesis and some protecting groups are removed from the added amino acid after coupling. This step is called "deprotection". It facilitates the binding of newly entered amino acids to the peptide chain. Upon completion, the remaining protecting groups were removed from the peptide.
Commonly used protecting groups: 1. N-terminal protecting groups: They are relatively easy to remove to form peptide bonds; such as tert-butoxycarbonyl (Boc) and 9-fluorenylmethoxycarbonyl (Fmoc). 2. C-terminal protecting group: liquid phase synthesis needs to protect the C-terminal, solid-phase synthesis does not need protection, because the solid support acts as a protecting group. 3. Amino acid side chains: They are called permanent protecting groups because they can withstand multiple cycles of chemical treatment during the synthesis stage and are only removed after the synthesis is complete.
The invention of synthetic peptides has encouraged the development of custom synthetic peptide services in numerous application areas, such as: development of epitope-specific antibodies, specifically for use against pathogenic proteins; protein function research, i.e. identification and characterization; research in enzymes such as kinases and proteases enzyme-substrate interactions. It is essential in cell signaling. Synthetic peptides can resemble natural peptides; therefore, they can be used as part of the treatment of major diseases. They can be used as reagents in mass spectrometry-based applications.