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Preservation of polypeptides

Issuing time:2018-12-03 14:36

Peptides in - 20 ℃ is stable, especially the freeze drying and stored in a dryer, before them exposed to air, freeze-drying peptides can be put in the room temperature. This will reduce the impact of humidity, and when freeze-drying is not possible, the best method is to store a small working sample.

For peptides containing Cys and Met orTrP, deoxy buffers are essential for dissolution because the peptides oxidize readily in the air and are reduced by nitrogen or argon, which slowly flows through the peptides before sealing. Polypeptides containing Gln or Asn are also easy to degrade, and all these peptides have a limited lifetime compared to those without these problematic glycosides. Solubility of polypeptides

The preferred solvent for most peptides is ultra-pure pumped water. Dilute acetic acid or ammonia are important for the dissolution of basic or acidic peptides, respectively. Insoluble peptides, these methods need to DMF, urea, guanidiniam chloride or acetonitnle to dissolve, these solvents may be some experiments have side effects. Therefore, we suggest to pay attention to the design of peptides.

Residues Ala, Cys, Ile, Leu, Met, Phe and Val will all increase the difficulty of peptide dissolution.

If you need special peptides or any technical assistance, please feel free to contact us. We assure you of your complete satisfaction, and will not charge you for the order in which we cannot properly synthesize. Preservation and manipulation of polypeptides

Packed in 1mg or less polypeptide by net weight, the declared vial weight does not contain relevant antiions or water. For example, if the peptide content determined by the amino acid analysis is 80% in a 1mg sample, the gross weight in the bottle is 1.25mg.

A large amount of polypeptides is gross recalculated. The weight indicated contains relevant antiions and water. For example, if the peptide percentage in the 25mg sample is 90%, the actual peptide amount is 25mg x 90%=22.5mg

Don't confuse the peptide content with its purity. The purity of the peptide may be 100%, while the content of the peptide is determined by the anti-ionic amount of the relevant charged groups (such as Arg, Lys) and the peptide hydrophilicity. This is the nature of synthetic peptides. Preservation of lyophilized peptides

All products should be stored in the refrigerator, it is best to - 20 ℃. Most peptides can be stored in this way for several years. Preservation of peptide solution

Peptide solution than freeze-dried form is not stable, the solution should be neutral pH (pH5-7), - 20 ℃ to save, to avoid the repeated freezing and thawing of the sample, had better deposit is divided into small kind. When a sample is not used up after thawing, it should be thrown away. Bacterial degradation can sometimes become a problem with solution peptides. To overcome this, the peptides should be dissolved in sterile water or filtered with a 0.2-m filter.

Peptide reconstruction and manipulation

Most peptides dissolve in sterile distilled water. During initial dissolution, care must be taken to make the initial concentration greater than the required concentration. If the polypeptide is only moderately soluble, this will permit the addition of other solvents or buffer salts.

If the peptides have limited solubility in water, there are several options to help them dissolve:

Dilute acetic acid (containing Arg, Lys, His) for basic peptides

Dilute ammonia water (including Asp, Glu) for acid peptides

Methanol (Acetonitnile, Methanol) with 10% of extremely hydrophobic peptide

DM50 or DMF is used for insoluble peptides

Guanicline hydrochloride or urea concentrated solution is very useful, share with these methods, acoustic processing is also the effective means of soluble polypeptide.

Application and preservation of polypeptides

Peptides are widely soluble. The major problem with insoluble peptides is the formation of secondary structures. This occurs with all but the most extreme peptides, especially in peptides with multiple hydrophobic residues. Salt promotes the formation of secondary structures. We recommend dissolving peptides in sterile distilled water or deionized water first. If the dissolution rate needs to be increased, sound processing can be used. Dissolution is still a problem, add a small amount of dilute acetic acid (10%) or ammonia, will facilitate dissolution.

To long-term preservation of peptides, freeze drying, best cold dry powder last few years in 20 ℃ or lower with little or no degradation. The peptides in solution are far from stable. Polypeptides are easily degraded by bacteria and dissolved in sterile purified water.

Polypeptide solutions containing residues of Met, Cgs or Try have limited lifetime due to oxidation. Should be dissolved in anaerobic solvents, in order to prevent repeated freeze-thaw damage, it is recommended to dissolve the excess peptide in the laboratory, and the remaining polypeptides are preserved in solid form.

HPLC analysis and purification

The analytical HPLC USES a column and pump system that can withstand high transmission pressures, which can be packed with very fine particles (3-10 m). The resulting peptide should be highly analyzed within minutes.

There are two types of HPLC: ion exchange and phase inversion. Ion exchange HPLC relies on direct charge interactions between peptides and solid phases. The column develops into an ion with a specific charge within a certain PH range, while a polypeptide or polypeptide mixture, consisting of its amino acids, exhibits an opposite charge. Separation is a charge interaction that elects peptides through a variable PH, ionic strength, or both, usually with a low ionic strength solution first, then gradually or step by step until the peptides elution in the flame column. An example of ion exchange separation is the use of a strong cation exchange column. Sulfoethylaspartimide, for example, is separated by a positive charge in an acidic PH.

The reverse phase HPLC condition is opposite to that of normal chromatography. The polypeptides are attached to the column by hydrophobic action and eluted by reducing ionic strength, as by increasing the hydrophobicity of the eluent. The column is usually made up of a chain of hydrocarbons covalently attached to the silicon with a length of g4-g8 carbon atoms. Because elution is a hydrophobic action. Long chains are better than short ones for small, highly charged peptides. Large hydrophobic peptides, on the other hand, were eluted with short chains. However, in general practice, there is little significant difference between the two types of column interconversion. Other types of carriers are composed of carbohydrates, such as phenyls.

The typical operation is usually composed of two kinds of infusion, 0.1% tfa-h2o and 80% acetonitrile. Mix with linear ladders at a rate of 0.5% to 1.0% change per minute. Common analysis and purification columns are 4.6 x 250mm(3-10 m) and 22 x 250mm(10 m). If the columns are filled radially, the sizes are 8 x 100 (3-10 m) and 25 x 250mm(10 m).

A large number of buffers contain many different reagents, such as heptafluorobutyric acid, 0.1% phosphoric acid, dilute He formic acid (5-6%, ph2-4), 10-100mm NH4HCO3, sodium acetate/ammonia, TFA/TEA, sodium phosphate or potassium, and isoamyl phenol. Many different combinations can form a buffer, but it is important to note that the reverse-phase silica column material cannot be exposed to a high pH or even a slightly alkaline pH for a long time, as this will damage the column.

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