Do You Know The Knowledge Of Peptides?

​A peptide is a polymeric organic compound in which various amino acid molecules are dehydrated to form a peptide bond. Unlike macromolecules, monomers that are basically constructed as peptide chains are various amino acid residues, and their side chain structures are different. Therefore the peptide is not a high molecular polymer. Compared with protein, the covalent bond of the peptide forms the same chain structure as the former, but the chain length and molecular weight are much smaller than the former. Therefore, the peptide is not a protein. Despite this, there are many similar physical and chemical properties between peptides and proteins, such as hydrophilicity, polarity, secondary structure, easy enzymatic hydrolysis, metal complexation and so on. It is difficult to distinguish peptides from proteins at an accurate value from the molecular weight. It has been customary to express the following according to the length of the peptide chain:

Less than 10 residues are oligopeptides or small peptide molecules. 10 to 80 (or 100) residues are peptides or peptides. More than 80 (or 100) residues are proteins, and others claim that only 150 or more residues are true proteins.

Dissolving peptides according to conditions

If the peptide is insoluble in pure water, sonication helps to break up the particles and increase solubility. Note: Sonication can cause solution heating and peptide degradation.

If the peptide contains multiple basic amino acids, a 1 to 10% aqueous solution of acetic acid is used; for a very hydrophobic peptide, 50% acetic acid is used.

If the peptide contains a large amount of acidic amino acids, it can be dissolved in a volatile alkaline buffer such as 1~10% ammonia solution or ethyl morphine or bicarbonate. The pH must be adjusted before chromatography.

Isopropanol and acetonitrile dissolve the medium size peptide. If the peptide is to be applied to the column, the amount of organic solvent must be small, otherwise the residence time will be seriously affected.

If the peptide synthesis is highly hydrophobic due to the aromatic side chain such as Val, Leu, Met, Phe, Tyr, Ala, or a neutral peptide, the use of a membrane denaturant such as DMF or DMSO contributes to the dissolution of the peptide.

a. High concentration membrane denaturing agents are solubilized by disrupting the secondary structure of the peptide.

b. Membrane denaturants are suitable for the preparation of peptide assays, but may interfere with the study of their biological activity.

c. DMF is the best denaturing agent (up to 30% concentration), added to the peptide to dissolve.

d. In reversed phase chromatography, DMF will flow out with the pre-eluent peak, which may be high depending on the amount of injection. Most peptides can flow out within a few minutes after a large amount of DMF efflux. If the peptide chain is small and elutes too early, the amount of peptide will decrease.

GT peptide is an expert at high-quality custom peptide synthesis for most biotech companies and academic institutes and consistently meets the highest standard of quality, customer service, and technical support. 

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