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Peptide Storage Guidelines

Storing peptides correctly is critical for maintaining their stability and biological activity over time. Proper storage protocols can prevent degradation, ensuring that the peptide remains effective for research, therapeutic, or other applications.

Understanding Peptide Stability

Peptides are chains of amino acids linked by peptide bonds. Their stability is influenced by several factors, including:

• Amino Acid Sequence: Certain amino acids, such as cysteine, methionine, tryptophan, and glutamine, are more susceptible to oxidation or degradation.
• Contaminants: The presence of proteases, bacteria, or other contaminants can lead to peptide breakdown.
• Environmental Conditions: Exposure to high temperatures, moisture, and light can accelerate degradation.

General Storage Guidelines

Initial Handling

Upon receiving a peptide, it's essential to check its form. Most are shipped as a lyophilized (freeze-dried) powder, which is the most stable form for long-term storage.

• As a Lyophilized Powder: Store the powder at -20°C or colder (e.g., -80°C). This form is highly stable and can be stored for several years. Keep the vial sealed tightly to prevent moisture absorption.
• As a Solution: Once dissolved, peptides are significantly less stable. Store solutions at -20°C or -80°C. Avoid storing peptide solutions at 4°C for extended periods.

Working with Peptide Solutions

When preparing a peptide solution, use a high-purity solvent, such as sterile, deionized water or an appropriate buffer.

Single-Use Aliquots

• Procedure: Dissolve the entire peptide vial in the appropriate solvent to create a concentrated stock solution. Then, aliquot this stock solution into smaller, labeled microcentrifuge tubes.
• Benefits: This method ensures that each time you need to use the peptide, you only thaw a small portion, preserving the integrity of the remaining stock.

Freezing and Thawing

• Freezing: Freeze the aliquots quickly by placing them in an ethanol/dry ice bath or a specialized freezer rack to avoid degradation.
• Thawing: Thaw the aliquots on ice or in a cold room. Avoid rapid thawing at high temperatures.

Specific Considerations

Peptides Containing Cysteine, Methionine, or Tryptophan

Peptides with these amino acids are prone to oxidation.

• Storage: Store under an inert atmosphere (nitrogen or argon) if possible.
• Solvent: Use deoxygenated solvents for reconstitution.
• Additives: Antioxidants or reducing agents (e.g., DTT) may help, but use cautiously as they can interfere with some assays.

Peptides Containing Glutamine or Asparagine

These amino acids are susceptible to deamidation.

• Storage: Store at the coldest possible temperature (-80°C) as a lyophilized powder.
• Solvent: For reconstitution, use a slightly acidic buffer (pH ~4-5) to slow deamidation.

Preventing Microbial Contamination

• Always use sterile techniques and solvents.
• Use sterile, single-use aliquots.
• Avoid sodium azide when it may interfere with downstream applications, especially cell-based assays.

Summary of Storage Conditions