Peptides synthesis, also called peptide chain synthesis, is a solid-phase synthesis. The sequence is generally synthesized from the C-terminal (carboxyl terminal) to the N-terminal (amino terminal). In the past, peptides synthesis was carried out in solution, which is called liquid phase synthesis. Peptides synthesis is mainly divided into two ways, including chemical synthesis of peptides and biosynthesis of peptides.
Custom peptides synthesis services are how to connect various amino acid units according to the sequence and connection mode of natural amino acids. Since amino acids exist in the form of zwitterions (H3+NCH(R)COO-) in the molecule under neutral conditions, the direct condensation between amino acids to form amide bonds is difficult under normal conditions.
The reactivity of amino acid esters is relatively high. Heated at 100℃ or placed at room temperature for a long time can be polymerized to form peptide esters, but the reaction is not directional. The two amino acid a1 and a2 esters will form a1a2, a1a1, a2a1 and other mixtures in any order during polymerization.
In order to obtain synthetic peptides with a specific sequence, arbitrary polymerization methods are not feasible, and only the directional peptides synthesis method of gradual condensation can be used. Generally, the amino or carboxyl group that does not need to be reacted is temporarily protected with an appropriate group, and then the ligation reaction is carried out to ensure the directional progress of the polypeptides synthesis.
The resulting ligation product is a protective peptide with protective groups at both the N-terminus and the C-terminus, and the free peptide can only be obtained after removing the protective group. If the peptide chain does not end here, but the peptide chain needs to be extended from the N-terminus or C-terminus, you can selectively remove X or Q first, and then combine it with a new N-protected amino acid (or peptide) or C-protection. The amino acid (or peptide) is connected for the second time, and this is repeated continuously until the required peptide chain length is reached.
For the synthesis of long peptides, there are generally two ways of elongating the peptide chain including gradual growth and fragment condensation. The former starts from the starting amino acid (or peptide). Each time it is connected, one amino acid is extended, and the latter is condensed with N-protected peptide and C-protected peptide to obtain a new long peptide chain with the added length of the two.
The amino acids with side chain functional groups in peptides synthesis such as glutamic acid, aspartic acid, lysine, arginine, histidine, cysteine, generally need to temporarily protect the side chain group with an appropriate protecting group in order to avoid the side effect of side chain.