Handling and Storage

Storage of Lyophilized Peptides

Lyophilized (freeze-dried) peptides exhibit optimal stability when stored at -20°C or below in sealed containers with desiccant. Under these conditions, most peptides remain stable for extended periods, though specific stability varies with sequence composition.

Short-term storage at 4°C is acceptable for routine laboratory use. Room temperature storage should be avoided for extended periods, particularly for peptides containing oxidation-sensitive residues.

Reconstitution Procedures

Peptide solubility depends on sequence composition. Charged and polar sequences dissolve readily in aqueous buffers, while hydrophobic sequences may require organic co-solvents or acidic/basic pH adjustment.

General approach: begin with small volumes of solvent, adding incrementally until dissolution. For difficult sequences, sonication or gentle warming may assist dissolution. Avoid vigorous vortexing, which can cause foaming and surface denaturation.

Solvent Selection

Common reconstitution solvents include sterile water, phosphate-buffered saline (PBS), dilute acetic acid, and DMSO. Solvent selection depends on peptide characteristics and downstream application requirements.

Solution Stability

Reconstituted peptide solutions are less stable than lyophilized forms. Aqueous solutions should be aliquoted into single-use volumes and stored frozen to avoid repeated freeze-thaw cycles, which can cause aggregation and degradation.

Solution stability varies with peptide sequence, concentration, pH, and buffer composition. Sequences containing methionine, cysteine, or tryptophan are particularly susceptible to oxidation in solution.

Handling Precautions

Allow lyophilized peptides to reach room temperature before opening vials to prevent moisture condensation on the cold powder. Work quickly when transferring material to minimize atmospheric exposure.

Use calibrated analytical balances for weighing, as peptide content (typically 70-90%) must be considered when calculating actual peptide mass. Electrostatic charge can cause powder to adhere to container walls; anti-static devices may assist handling.

Concentration Determination

For accurate concentration determination, UV spectroscopy using calculated molar extinction coefficients provides reliable results for peptides containing aromatic residues. Amino acid analysis offers an alternative method independent of chromophore content.

Weight-based concentration calculations must account for peptide content, counterion content, and moisture. Direct spectroscopic measurement provides more accurate results for critical applications.