The peptides are stable at -20 DEG C and, in particular, are freeze-dried and stored in a direct fired dryer. The freeze-dried peptides can be placed at room temperature before exposing them to air. This will reduce the impact of humidity, and when freeze-drying is not possible, the best way is to store it in small working samples.
For polypeptides containing Cys, MetorTrP, deoxidation buffers are essential for their dissolution, because this polypeptide can be easily oxidized by air, and nitrogen or argon gas flowing slowly through the polypeptide will also reduce oxidation before sealing the bottle. Peptides containing Gln or Asn are also easily degraded, and all of these peptides have a limited lifetime compared to those that do not contain these problematic glycosides.
Solubility of Peptides：
The preferred solvent for most peptides is ultrapure pumped water. Dilute acetic acid or ammonia are important for dissolution of alkaline or acidic peptides, respectively. These insoluble peptides require DMF, urea, guanidiniam chloride, or acetonitnle for dissolution, which may have side effects in some trials. Therefore, we recommend that attention be paid to the design of peptides.The residues Ala, Cys, Ile, Leu, Met, Phe and Val all increase the solubility of the peptides.
You need special peptides or any technical assistance, please feel free to contact us. We guarantee your complete satisfaction, and we do not charge for orders that we cannot properly synthesize. Preservation and manipulation of peptides
Polypeptides of 1 mg or less are packaged as net weight, and the declared vial weight does not contain relevant anti-ion and water. For example, amino acid analysis determines the peptide content is 80%, in a 1 mg sample, then the gross weight in the bottle is 1.25 mg.
A large number of peptides are calculated in gross weight. The labeled weight contains the relevant anti-ion and water, for example, if the percentage of peptides in a 25 mg sample is 90%, then the actual peptide amount is 25 mg × 90% = 22.5mg
Don’t confuse peptide content with purity. The purity of the peptide may be 100%, while the peptide content depends on the ion resistance of charged groups (e.g. Arg, Lys) and the hydrophilicity of the peptide. This is the nature of synthetic peptides. Preservation of lyophilized peptides
All products should be stored in the refrigerator, preferably at -20 ° C. Most peptides can be stored for several years in this way. Preservation of peptide solution The peptide solution is far less stable than the lyophilized form, the solution should be neutral pH (pH5-7), -20C preservation, in order to avoid repeated freezing and thawing of the sample, it is best to divide into small samples. A sample is not used after thawing, it should be thrown away, bacterial degradation sometimes becomes the trouble of the solution peptide, to overcome this, the peptide should be dissolved in sterile water, or the peptide solution is filtered with 0.2 μM filter.
Reconstruction and manipulation of peptides:
Most peptides dissolve in sterile distilled water. When first dissolving, care should be taken to make the initial concentration greater than the required concentration, if the polypeptide has only limited solubility, this allows the addition of other dissolving agents or buffer salts.
If the polypeptide has limited solubility in water, there are several options to help dissolve:
Dilute acetic acid (containing Arg, Lys, His) for alkaline peptides
Dilute ammonia water (containing Asp, Glu) for acidic peptides
Parahydrophobic peptides with 10% organic modification (Acetonitnile, Methanol)
Highly insoluble peptides with DM50 or DMF
Concentrated solutions of guanicline hydrochloride or urea are also useful, in conjunction with the above methods, and acoustic treatment is also an effective means of dissolving polypeptides.
Application and preservation of peptides：
Peptides have a wide range of solubility. The main problem of polypeptide insoluble is the formation of secondary structure. This occurs except for the teratopeptide, especially in peptides with multiple hydrophobic residues. Salt can promote the formation of secondary structure. We recommend dissolving peptides in aseptic distilled water or deionized water first. If it is necessary to increase the dissolution rate, acoustic treatment can be used. Dissolution is still a problem, adding a small amount of dilute acetic acid (10%) or ammonia will be easy to dissolve.
To preserve peptides for a long time, it is best to freeze-dry, cold-dried powder can be stored at-20 ℃ or lower for a few years without degradation. The peptides in the solution are far from stable. Peptides are easily degraded by bacteria and dissolved in aseptic purified water.
The polypeptide solution containing Met, Cgs or Try residues has limited life due to oxidation. In order to prevent repeated freeze-thaw damage, it is suggested that the excess peptides should be dissolved in the stool experiment, and the rest of the peptides should be preserved in solid form.
HPLC Analysis and Purification
Analytical HPLC uses a column and pump system that can withstand the transfer pressure, which allows very fine particles (3-10 μm) to be used as fillers. The polypeptide is highly analyzed within minutes.
There are two types of HPLC: ion exchange and reverse phase. Ion exchange HPLC relies on direct charge interactions between peptides and solid phases. A column with a specific charge evolves into a plasma over a certain pH range, while a polypeptide or polypeptide mixture exhibits the opposite charge due to its amino acid composition. Separation is a charge interaction in which polypeptides are eluted by varying pH, ionic strength, or both, usually with a solution of low ionic strength and then gradually or step by step until the polypeptide is eluted from a column of fire. An example of ion exchange separation using a strong cation exchange column is presented. For example, sulfoethylaspartimide is separated by a positive charge in acidic PH.
The reverse phase HPLC condition is opposite to normal chromatography. The polypeptide is attached to the column by hydrophobic interaction and eluted with reduced ionic strength, such as increasing the hydrophobicity of the eluent. Usually, the column is composed of hydrocarbon alkanes covalently adsorbed on silicon, which are G4 to G8 carbon atoms in length. Because the elution is a hydrophobic action. Long chain columns are better than short chain pairs for small, highly charged peptides. On the other hand, large hydrophobic peptides were eluted with short chain columns. However, in general practice, the two types of columns are not significantly different from each other, and the other types of carriers are composed of carbohydrates, such as phenyl groups.
The typical operation is often composed of Liangshou granules, 0.1% TFA-H2O and 80% acetonitrile 0.1% TFA–H2O dilute acetonitrile. Mix at a rate of 0.5% to 1.0% change per minute using linear gradient. Common analysis and purification columns are 4.6 × 250 mm (3-10μm)