Peptide Storage
Jul 30, 2024
4 min read
Written by Johnathon Anderson, Ph.D., a research scientist specializing in regenerative medicine and serving as an Associate Professor at the University of California Davis School of Medicine
Why Is Proper Peptide Storage Important?
Proper peptide storage is important to maintain peptide quality and ensure reliable research results. If peptides experience contamination, oxidation, aggregation, or degradation this will compromise your experiments. While peptides vary in stability, adhering to these guidelines will significantly extend their shelf life.
Peptide Storage Do’s and Don’ts
The best peptide storage tips are:
Keep peptides cold, dry, and away from light.
Avoid freeze-thaw cycles.
Minimize air exposure.
Use light-blocking storage.
Store peptides in solution only when ready to use.
Aliquot peptides based on experimental needs.
These best practices will help maintain peptide integrity for consistent, reliable results in your studies.
How Do You Store Powdered, Freeze-Dried Peptides?
Powdered, freeze-dried peptides can be stored at room temperature (20°C or 70°F) for extended periods, or in the refrigerator (4°C or 39°F) or freezer (-20°C or 0°F) for years. To avoid peptide degradation, avoid repeated freeze-thaw cycles, and only use a non-frost-free freezer to prevent temperature fluctuations.
What Degrades Peptides?
Peptides are degraded by exposure to moisture and to air, and microbial contaminants.
How Do You Avoid Powdered, Freeze-Dried Peptides Being Exposed To Moisture?
Powdered, freeze-dried peptides should not be exposed to moisture by allowing them to reach room temperature before opening, once they’ve been taken out of the freezer. This prevents moisture from condensing on the cold peptide or inside its container.
How Do You Avoid Powdered, Freeze-Dried Peptides Being Exposed To Air?
Powdered, freeze-dried peptides should not be exposed to air by keeping the peptide containers closed as much as possible. After use, reseal containers with dry, inert gas (like nitrogen or argon) to prevent oxidation. Peptides containing cysteine (C), methionine (M), or tryptophan (W) are especially prone to air oxidation. For best results, aliquot peptides into smaller vials to minimize repeated freeze-thaw cycles and air exposure.
How Do You Properly Store Peptides Once They Are Reconstituted In A Solution?
Peptides reconstituted in a solution should be refrigerated at 4°C (39°F) for up to 30 days, and maintained in sterile, bacteriostatic buffers with a pH of 5-6.
Which Peptides Degrade The Most?
The peptides that degrade the most contain certain amino acids such as cysteine (Cys), methionine (Met), tryptophan (Trp), aspartic acid (Asp), glutamine (Gln), and N-terminal glutamic acid (Glu), and they are especially unstable when reconstituted in a solution.
What Are The Best Containers For Peptides?
The best containers for peptides are glass vials because they are resistant to chemicals, durable, and transparent. The second best option for peptide containers are plastic vials, where options include polystyrene (transparent but less resistant to chemicals) and polypropylene (translucent but more resistant). Although peptides are sometimes shipped in plastic to prevent breakage, transferring them to glass vials can improve stability.
What Solution Works Best Reconstituting Peptides from Peptide Systems?
The best solution for reconstituting peptides from Peptide Systems is bacteriostatic water.
What Are The Guidelines For Dissolving Charged And Hydrophobic Peptides
Identifying Solubility Type
To dissolve peptides effectively, start by identifying the peptide’s solubility type. Follow these guidelines based on the peptide’s net charge:
1. Acidic Peptides (Net Charge is Negative)
If a peptide has a negative net charge, it is acidic. For acidic peptides, or if more than 25% of residues are charged at pH 7, use 0.1 M ammonium bicarbonate to dissolve the peptide. Then, dilute with water to reach the desired concentration. Ensure the solution’s pH is close to 7, adjusting as necessary.
2. Basic Peptides (Net Charge is Positive)
Peptides with a positive net charge are basic. If the peptide’s charged residues make up between 10–25% of the total residues at pH 7, dissolve it with a small amount of 25% acetic acid and dilute with water to the desired concentration.
3. Neutral Peptides (Net Charge is Zero)
A peptide is neutral if its overall net charge is zero. If over 25% of residues are charged, follow the dissolving method for acidic peptides.
Additional Dissolving Tips
Low-Charge Peptides: If less than 10% of residues are charged, use organic solvents for dissolution.
Sonication: Before trying stronger solvents, sonicate the solution to improve solubility by breaking down the solid peptide. If the solution appears cloudy or gelled after sonication, a stronger solvent may be required. If needed, lyophilize the peptide, then try another solvent.
Dissolving Hydrophobic or Uncharged Peptides
For peptides with high hydrophobic content (more than 50% hydrophobic residues) or low charge (neutral peptides with less than 25% charged residues):
Use Organic Solvents: Acetonitrile (ACN), dimethyl sulfoxide (DMSO), or dimethylformamide (DMF) are effective solvents. Peptides with cysteine (C) and methionine (M) may be unstable in DMSO, so proceed with caution.
Add Chaotropic Compounds: To disrupt hydrophobic interactions, add chaotropic agents like guanidine hydrochloride or urea.
Initial Solvent Use: Begin dissolving in an organic solvent rather than a water/solvent mix, as dissolution rates are generally higher.
Once dissolved, add the peptide solution slowly to the buffered solution while stirring gently. This gradual addition prevents precipitation and allows visual monitoring.
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Jul 30, 2024
4 min read
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