Peptide Synthesis - Process and Uses
Peptides are organic substances made up of tiny molecules with chemical structures similar to protein structures. The principal difference is that it is necessary for protein chain structures to correctly fold into specific shapes to carry out a biological activity, which is not essential in the case of peptides. Each peptide molecule comprises two or more amino acids linked by amide type of peptide bonds. While peptides occur naturally within humans, animals, and plants, it is also possible to carry out synthetic peptide synthesis to produce peptide compounds for use in medical drugs, vaccines, antigens, and biomaterials.
What Is Peptide Synthesis?
Peptide synthesis is a chemical process in organic chemistry that a peptide synthesis company conducts to produce peptide compounds. It involves the formation of short peptide chains by linking multiple amino acids together. Each chain may contain anywhere from two to 70 amino acids. By carrying out synthetic peptide synthesis, it is possible to create peptide sequences to represent epitopes, or antigenic determinants that are part of specific structural and functional protein units, also known as protein domains, and can stimulate immune responses.
The T cells and B cells of the immune system recognize that epitopes are parts of the antigens, and the paratope parts of the complementary antibodies bind to these epitopes. That has immense implications for scientific and medical research. With technological advancements that have improved the peptide synthesis method, there has been a significant increase in commercial and pharmaceutical products containing synthetic peptides. These include synthetically produced Adrenocorticotropic hormone, calcitonin, and oxytocin hormones for healing and immune research, and the artificial sweetener aspartame.
How Are Peptides Synthesized?
Peptides are chemically synthesized by linking two or more amino acids together. In the peptide synthesis process, the C-terminus or carboxyl group of one amino acid gets attached to the N-terminus or amino group of another amino acid. While there are around 500 naturally occurring amino acids, including alanine, arginine, cysteine, glutamate, and proline, it is possible to synthesize many more amino acids to create new peptides for various purposes.
The main concern during the peptide synthesis process is that there can be many reactive groups in amino acids. When these groups interact with one another during the synthesis process, there is a high possibility that unwanted reactions could occur. These could cause the peptide chain to remain unduly short or give rise to undesired branches. It could lead to the production of substandard peptides, or there is likely to be a low yield of peptides. It might help to deactivate some of the reactive amino acid groups or protect them during the synthesis process to obtain the desired outcome.
Use of Protecting Groups in Peptide Synthesis
There are three categories of specifically engineered protecting groups to prevent polymerization and unwanted chemical reactions during the peptide synthesis process. They must be easy to introduce, remain stable during chemical reactions, and be safe to remove afterward with an amine base, acid, or heat. These protecting groups help maximize yield and support the formation of complex peptide structures. They are:
- N-terminal protecting groups—These amine or ammonium cation groups protect the peptide structure's N-terminus, which is the end part that contains an amino acid inside a peptide that is not a part of the amide or peptide bond.
- C-terminal protecting groups—These groups protect the C-terminus, which is the end of the peptide chain containing a free carboxyl group (-COOH).
- Side chain protecting groups—They protect the amino acid side chains and can remain stable through many chemical treatment cycles.
What Are Some Peptide Synthesis Processes?
Peptide synthesis processes include the following:
- Solution phase synthesis—The liquid phase peptide synthesis involves synthesizing single amino acids in a solution and then linking them together to form a peptide chain.
- Solid-phase peptide synthesis—The process involves using a solid, such as a resin, as a support for attaching an amino acid with a protective group and then removing the protective group and washing the resin before repeating the process.
Scientists use reverse-phase chromatography and high-performance liquid chromatography purification methods during the peptide synthesis processes to remove impurities and get optimal yields.