What Is a Synthetic Peptide?

Techniques for peptide synthesis are techniques that use chemical means to sequentially condense amino acids into peptides or proteins. Most natural peptides and proteins are made up of a-amino acids. There can be 3 chemically active groups in the amino acid molecule, namely side chains, amino groups and carboxyl groups, which are covalently linked to the a-carbon atom.

Techniques for peptide synthesis are techniques that use chemical means to sequentially condense amino acids into peptides or proteins. Most natural peptides and proteins are made up of a-amino acids. There can be 3 chemically active groups in the amino acid molecule, namely side chains, amino groups and carboxyl groups, which are covalently linked to the -carbon atom. ^[1]

There are two basic methods for chemically synthesizing peptides:

Synthetic peptide technology

That is, the reactants undergo homogeneous condensation in a completely dissolved state. Since the by-products of each step of the condensation product can be removed by crystallization or washing, the quality of the peptide synthesized in the liquid phase is higher, but it takes more time, complicated procedures and lower yield. In 1965, Chinese scientists synthesized crystalline bovine insulin by this method. The production process of the midwifery drug oxytocin (a nonapeptide) still uses the liquid phase process.

Solid phase method

One of the reactants takes a solid phase state. The reaction product can be recovered by filtration and washed to remove unreacted substances because it is covalently connected to the resin, so the operation is simple, and it is easy to standardize and mechanize. In fact, solid-phase peptide synthesizers have been widely used. The disadvantage of this method is that the side reactants will continuously accumulate on the resin, which is difficult to remove. And the more the reaction times, that is, the longer the target peptide, the more the by-products accumulate, and finally the main product will be submerged in impurities and cannot be separated. Therefore, although the establishment of this method prompted RBMerrifield to win the Nobel Prize in Chemistry, it is still limited to a synthetic level of about 30 peptides in practice. In order to overcome this shortcoming, some people use the liquid phase method to synthesize high-purity small peptides for solid-phase condensation to reduce the total number of solid-phase condensations, which becomes the solid-phase fragment condensation method. China has successfully synthesized large peptides and proteins such as crystal islet glucagon and snake venom membrane toxin using this method. In addition to chemical methods, the use of reverse reactions of proteolytic enzymes can also enzymatically synthesize certain specific peptide bonds. ^[1]