Reconstitution
Lyophilized Peptides
Peptides are commonly supplied in a lyophilized (freeze-dried) powder form. Lyophilization is a process in which water is removed from a compound after it is frozen and placed under a vacuum, allowing the ice to change directly from solid to vapor without passing through a liquid phase. Lyophilized peptides commonly resemble a small white “puck” that may have a fluffy or more granular appearance. Different lyophilization techniques can yield a more voluminous (fluffy) or a more compacted (granular) lyophilized peptide.
Reconstituting Peptides
Before lyophilized peptides can be utilized in the lab, they have to be reconstituted; that is, they must be dissolved in a liquid solution. Unfortunately, there is not a “one size fits all” solvent that will solubilize all peptides while maintaining peptide integrity and compatibility with biological assays. While sterile, distilled water or regular bacteriostatic water is the first choice, this will not dissolve all peptides. As a result, the researcher may have to undertake a trial and error approach and attempt to dissolve the peptide in increasingly stronger solvents. Sodium Chloride water is NOT recommended due to its tendency to cause precipitates with acetate salts.
A peptide’s polarity is the main factor by which its solubility is determined. Basic peptides can be dissolved in acidic solutions, and, conversely, acidic peptides can be reconstituted in basic solutions. Additionally, hydrophobic peptides, as well as neutral peptides that contain numerous hydrophobic or polar uncharged amino acids, should be dissolved in organic solvents. Examples include acetic acid, propanol, isopropanol, and DMSO. The amount of organic solvent used should be small, however. Once the peptide is dissolved in the solution, then dilution with sterile water or bacteriostatic water should be performed. Sodium Chloride water is NOT recommended due to its tendency to cause precipitates with acetate salts. Importantly, peptides with methionine or free cysteine should not be dissolved in DMSO. Side-chain oxidation may occur, rendering the peptide unfit for laboratory experimentation.
Peptide Reconstitution Guidelines
Generally, it is advised to first attempt to dissolve peptides in solvents that are easy to remove by lyophilization. This is a precaution: in case the initial solvent is not effective, it can be removed again by the lyophilization process. Typically, the researcher should first attempt to dissolve the peptide in sterile distilled water or regular bacteriostatic water or in sterile dilute acetic acid (0.1%) solution. As a general guideline, it is recommended to test a small portion of the peptide for solubility in the chosen solvent before attempting to dissolve the entire peptide.
Importantly, the initial use of sterile water (or dilute acetic acid) will allow the researcher to dry the peptide without any unwanted residues in case the peptide fails to dissolve. Once the initial ineffective solvent is removed, the researcher can then attempt to dissolve the peptide in increasingly stronger solvents.
Additionally, researchers should dissolve the peptide in a sterile solvent to give a stock solution that is at a higher concentration than required for the assay. If the assay buffer is used first and the peptide does not dissolve, it can be very difficult to recover the peptide unadulterated. However, the peptide can always be diluted further with the assay buffer later on.
Peptide Storage
ALL ARTICLES AND PRODUCT INFORMATION PROVIDED ON THIS WEBSITE ARE FOR INFORMATIONAL AND EDUCATIONAL PURPOSES ONLY. The products offered on this website are furnished for in-vitro studies only. In-vitro studies (Latin: in glass) are performed outside of the body. These products are not medicines or drugs and have not been approved by the FDA to prevent, treat or cure any medical condition, ailment or disease. Bodily introduction of any kind into humans or animals is strictly forbidden by law.
Best Practices For Storing Peptides
Peptide Storage
ALL ARTICLES AND PRODUCT INFORMATION PROVIDED ON THIS WEBSITE ARE FOR INFORMATIONAL AND EDUCATIONAL PURPOSES ONLY. The products offered on this website are furnished for in-vitro studies only. In-vitro studies (Latin: in glass) are performed outside of the body. These products are not medicines or drugs and have not been approved by the FDA to prevent, treat or cure any medical condition, ailment or disease. Bodily introduction of any kind into humans or animals is strictly forbidden by law.
Best Practices For Storing Peptides
To preserve the integrity of laboratory results, proper storage of peptides is essential. Correct storage practices can maintain peptides for years and guard against contamination, oxidation, and degradation that may render your peptides, and therefore experiments, useless. While some peptides are more susceptible to degradation than others, knowing and implementing the best practices for peptide storage can greatly lengthen their stability and integrity regardless of composition.
Once peptides have been received, it is imperative that they are kept cold and away from light. If the peptides will be used immediately, or in the next several days, weeks or months, short-term refrigeration under 4C (39F) is generally acceptable. Lyophilized peptides are usually stable at room temperatures for several weeks or more, so if they will be utilized within weeks or months such storage is typically adequate.
However, for longer term storage (several months to years) it is more preferable to store peptides in a freezer at -80C (-112F). When storing peptides for months or even years, freezing is optimal in order to preserve the peptide’s stability.
Additionally, it is important to avoid repeated freeze-thaw cycles. This can increase the peptide’s susceptibility to degradation. Also, frost-free freezers should be avoided to store peptides, as temperatures can fluctuate widely during defrosting cycles.
Preventing Oxidation and Moisture Contamination
It is imperative to avoid contaminating peptides with both air and moisture. Moisture contamination is especially prone to occur when using a peptide immediately after withdrawing it from the freezer. To prevent uptake of moisture from the air on the cold surface of the peptide or on the inside of its container, allow the peptide to come to room temperature before opening.
It is also crucially important to minimize a peptide’s exposure to the air. A peptide’s container should therefore be kept closed as much as possible. After the required amount of peptide has been removed, resealing the container under an atmosphere of dry, inert gas (such as nitrogen or argon) will minimize the potential for the remaining peptide to become oxidized. Peptides with sequences C (cysteine), M (methionine), and W (tryptophan) are especially prone to air oxidation.
Because frequent thawing and refreezing as well as exposure to air can greatly reduce a peptide’s long-term stability, many researchers prefer to determine each experiment’s required amount of peptide and then aliquot this amount into separate vials as necessary. This is a highly useful preventative measure against peptide degradation.
