Peptides are macromolecules, and each peptide sequence has its own unique properties in terms of physical and chemical properties. Some peptides are difficult to synthesize, while others are relatively easy to synthesize but difficult to purify. They are mainly insoluble in water, so in purification, those hydrophobic peptides must be dissolved in non-aqueous solvents or special buffers. However, these solvents or buffers may not be suitable for use in biological experimental systems, and researchers cannot use the peptides to achieve research purposes.
　　
After years of exploration and accumulation, the synthesis personnel of BOSEN Company provide some suggestions for researchers' peptide design:
　　
Turning difficult into easy
　　
1. Reducing sequence length leads to an increase in peptide length, resulting in a decrease in crude product purity. Peptides with less than 15 residues are easier to obtain When the number of peptide chains increases to 20 or more, the amount of normal product needs to be considered. In practical applications, residues below 20 often yield better results.
　　
2. Reduce hydrophobic residues in peptides where hydrophobic residues have a significant advantage, especially in the region 7-12 residues away from the C-terminus, which can cause synthesis difficulties. It is generally believed that non pairing occurs due to the formation of beta folding sheets during synthesis. Of course, several polar residues can be substituted or Gly or Pro can be added to easily open the peptide structure, which may be helpful.
　　
3. Reducing "difficulty" residues. Multiple Cys, Met, Arg, and Try residues are generally difficult to synthesize. Ser can usually be used as a non oxidative substitute.
　　
Improve solubility
　　
1. We propose to change the N-terminal or C-terminal acidic peptide (which carries a negative charge at pH 7); Acetylation at the N-terminus while maintaining a free carboxyl group at the C-terminus to increase negative charge. Alkaline peptides (positively charged at pH 7) aminate the N-terminal free amino group to increase positive charge.
　　
2. Shorten or lengthen sequences. Some sequences contain a large number of hydrophobic amino acids, such as Trp, Phe, Val, Ile, Leu, Met, etc
　　
Tyr, Ala, etc. are usually difficult to dissolve when these hydrophobic residues are greater than 50%. Extending the sequence may be helpful in increasing the polarity of the peptide. Another option is to reduce the length of the peptide chain by decreasing hydrophobic residues to increase polarity. The higher the polarity of the peptide chain, the more likely it is to dissolve in water.
　　
3. Adding soluble residues can improve the solubility of some polar amino acids. Acidic peptides can be added at the N-terminus or C-terminus
　　
Glu Glu. Basic peptides can add Lys Lys at the N-terminus or C-terminus if charged groups cannot be added. Ser Gly Zer can be added to either the N-terminus or C-terminus. However, this method does not work when the two ends of the peptide chain cannot be changed.
　　
4. Changing the solubility of a sequence peptide chain by replacing one or more residues can be improved by altering certain residues in the sequence. Generally, replacing a single residue can significantly alter its hydrophobicity. And this change is relatively conservative, such as replacing Ala with Gly
　　
5. Choose different "frameworks" to change the sequence. If a sequence can be used to prepare many peptides of a certain length that are connected or overlap with each other, the purpose of changing the sequence can be achieved by changing the starting point of each peptide. The principle is to create a new and better balance between hydrophilic and hydrophobic residues of the same peptide, or to put "difficult" residues of the same peptide (such as two Cys) into two different peptides instead of gathering them in the same molecule.
　　
Beijing Boaoson Biotechnology Co., Ltd. - Peptide Synthesis Room