1. Preservation

2. Solubility

3. Save operation

4. Preservation of lyophilized peptides

5. Preservation of peptide solution

6. Peptide reconstruction and operation

7. Packaging of polypeptide

8. Peptide application preservation

9. Solid phase peptide synthesis of Fmoc

Preservation

Most peptides are stable at - 20 ℃, especially freeze-dried and stored in a desiccator, which can be placed at room temperature before they are exposed to air. This will reduce the impact of humidity, when it is not possible to freeze-drying, the best way is to store a small amount of working samples.

For peptides containing Cys and met ortrp, deoxidizing buffer is essential for their dissolution, because this peptide can be easily oxidized by air, and the nitrogen or argon slowly flowing through the peptide before sealing the bottle will also reduce the oxidation. Peptides containing Gln or ASN are also easy to degrade, and all of these peptides have a limited life span compared to those without these problematic glycosides.

Solubility

The channel selection solvent of large polypeptide is ultrapure air extraction water. Dilute acetic acid or ammonia are important for the dissolution of basic or acid peptides, respectively. These insoluble peptides need DMF, urea, guanidiniamchloride or acetonitnle to dissolve. These solvents may have side effects in some experiments. So we suggest that we should pay attention to peptide design.

The residues ala, Cys, ile, Leu, met, Phe and val will all increase the difficulty of peptide dissolution.

Save operation

The polypeptides packed in 1mg or less are packed in net weight, and the stated vial weight does not contain relevant anti ion and water. For example, the peptide content determined by amino acid analysis is 80%. In 1mg sample, the gross weight in the bottle is 1.25mg.

A lot of polypeptides are counted by wool. The marked weight contains relevant anti ion and water. For example, if the percentage of peptide in 25mg sample is 90%, then the actual peptide content is 25mg × 90% = 22.5mg

Don't confuse peptide content with purity. The purity of peptide may be 100%, but the content of peptide depends on the amount of anti ion and the new water property of peptide. This is the nature of synthetic peptides.

Preservation of lyophilized peptides

All products should be stored in refrigerator, preferably - 20 ℃. Most peptides can be stored in this way for several years.

Preservation of peptide solution

The peptide in solution is far more unstable than freeze-drying. The solution should be kept at neutral pH (ph5-7) and - 20 ℃. In order to avoid repeated freeze-thaw of the sample, it is better to store it in small samples. If a sample is not used up after thawing and freezing, it should be thrown away. Bacterial degradation may sometimes become a problem for peptide solution. To overcome this, peptide should be dissolved in sterile water, or peptide solution should be filtered with 0.2 μ M filter membrane.

Peptide reconstruction and operation

Most peptides are soluble in sterile steam water. When dissolving for the first time, pay attention to make the initial concentration larger than the required concentration. If the polypeptide only has limited solubility, it is allowed to add other dissolving agent or buffer salt.

If the solubility of polypeptides in water is limited, there are several options to help dissolve:

Dilute acetic acid for basic peptide (including Arg, Lys, his)

Dilute ammonia for acid peptide (including ASP, Glu)

10% organic modifier (acetonitnile, methanol) for hydrophobic peptides

Dm50 or DMF for very insoluble peptides

The concentrated solution of guanicline hydrochloride or urea is also very useful. In combination with the above methods, acoustic treatment is also an effective way to dissolve polypeptide.

Packaging of polypeptide

The purity of all polypeptides in the catalogue is 95-98%, unless otherwise specified. The packaging is small bottles of freeze-dried powder. Unless otherwise specified, peptide net weight package, for example, 1mg bottle of β - amloid1-40 contains exactly 1mg of peptide. The net weight of peptide was calculated from the peptide content obtained from amino acid analysis. For example, the gross weight of a polypeptide sample is 5mg, the amino acid content is 85%, and the net weight of polypeptide is 5mg × 0.85 = 4.25mg.

Please note that the peptide content is not the purity of the peptide, and the properties of the peptide synthesized by the anti ion, such as acetate and solvent, especially the water binding amount. The purity of polypeptide may reach 100%, but the content of polypeptide in the synthetic product is composed of amino acid, sulfur water, and the exposure of polypeptide to solvent and ion. Especially in the purification process, no matter how pure the polypeptide is, the content of polypeptide in freeze-dried powder is generally 70-85%. The remaining 15-30% is composed of other basic non peptide components.

Peptide application preservation

The peptide has a wide range of solubility. The main problem of peptide insolubility is the formation of secondary structure. Except for the most peptide, this happens, especially in the peptide with multiple hydrophobic residues. Salt will promote the formation of secondary structure. We recommend dissolving peptides in sterile distilled water or deionized water first. If the dissolution rate needs to be increased, acoustic treatment can be used. There is still a problem in dissolution. Adding a small amount of dilute acetic acid (10%) or ammonia water will facilitate dissolution.

To preserve peptides for a long time, it is best to freeze dry them. Cold dry powder can be stored at - 20 ℃ or lower for several years without degradation. The polypeptides in the solution are far from stable. The polypeptide is easy to be degraded by bacteria and dissolved by sterile purified water.

Peptide solutions containing met, CGS or try residues have limited life due to oxidation. It should be dissolved in an oxygen-free solvent. In order to prevent the damage of repeated freezing and thawing, it is suggested to dissolve the excess peptide in the stool test, and the remaining peptides should be stored in solid form.

Solid phase peptide synthesis of Fmoc

The key link of any polypeptide chain is peptide bond, which is formed by the condensation of one amino acid's amino acid with another. Generally, an amino acid consists of a central carbon atom surrounded by four other groups: amino group, carbonyl group, radical and side chain. Side chains, called R, differentiate the structure of different amino acids. Some side chains contain functional groups that interfere with the formation of peptide bonds. Therefore, it is very important to close the side chain functional groups.

The above figure shows the general process of Fmoc synthesis. First, the first Fmoc amino acid is connected to the insoluble carrier resin through an acid connector. Fmoc deprotection is completed by treating the resin with alkali, generally poperidine. The second Fmoc amino acid was linked by pre activation or in situ activation. It is required that after the synthesis of the total peptide, the resin be removed and deprotected by TFA separation.

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Chengdu Shengnuo Biotechnology Co., Ltd. has "Chengdu polypeptide drug engineering technology research center" in Chengdu, mainly engaged in polypeptide, polypeptide drug and beauty peptide research. Our zero defect has passed the FDA certification, and now it has become the first-class professional peptide drug and product development, technology transfer, technical service and peptide drug industry in the scale production and export of China's parks.