A common misconception about peptides is that peptides are as unstable as proteins. In fact, polypeptides are much more stable than proteins, because the two factors that affect the stability of proteins do not exist in polypeptide synthesis. These two factors are the third fold and protease contamination.
Proteins are easily transsexual because their tertiary structures are connected by non-covalent bonds, such as electrostatic interactions and hydrophobic interactions. Due to the short length, most peptides do not have enough of this interaction to fold each molecule into a prescribed tertiary structure. As a result, polypeptides cannot be denatured as proteins. Under this assumption, polypeptides can only be destroyed by covalent modification or peptide bond rupture. Unlike proteins, which are purified from cells filled with various proteases, the opportunity for synthetic peptides to be contaminated with proteases is extremely small.
Reactions can damage polypeptides that require extreme pH levels for oxidation. Under neutral pH, most biological experiments are slow. Bacterial contamination may be a more serious threat than those reactions, because peptides are a good source of nutrients for bacteria. Therefore, the solvent filtration is more important than the stability of polypeptides.
In normal conditions, the polypeptide solution can be kept for several days at room temperature, for several weeks at 4℃ and for several months or more at -20 ℃. Freeze-dried peptide powder can be kept for several months at room temperature and for several years at -20 degrees.