Alexa Fluor Dye-labeled Peptide Synthesis Service

What is the delivery format?

Our standard peptides are delivered lyophilized with trifluoroacetate (TFA) as a counterion and packaged in glass vials, stored under argon to protect from oxygen. For additional formats, such as delivery in low-binding plastics or 2-D barcoded plates, or in-solution with different solvents, please inquire.

What is your quality control (QC)?

The detailed spectra are included on the Certificate of Analysis for your records. Additional quality controls such as amino acid analysis (AAA) and further nonstandard analysis are available on request.

Q. How should peptides be stored?

A. We recommend preparing single-use aliquots and storing the products immediately at –20°C, upon receipt. In this manner, the lyophilized peptides are stable for several years. Solubilized peptides should be used immediately because they are unstable (the lower the concentration, the more unstable the peptides are). Any remaining peptides in solution should be re-lyophilized for longer storage.

Q. How should peptides be handled?

A. Always wear gloves when working with peptides to avoid contamination (e.g., enzymatic, bacterial, etc.). As many peptides are light-sensitive, they should also be protected from direct light. Avoid repeated freeze-thaw cycles.

Q. How are peptides solubilized?

A. Peptides are complex biomolecules, and each peptide has unique chemical and physical properties because of the unique amino acid composition. Although some peptides are easy to dissolve in aqueous solutions, peptides are often insoluble, especially when they contain long stretches of hydrophobic amino acids.

General guidelines for solubilizing peptides:

Because of the unique solubility of each peptide, we recommend first testing the solubilization of each peptide with a small amount of product.

1. Always use sterile water or buffer [phosphate buffered saline (PBS), Tris or phosphate, pH 7] to solubilize peptides.
2. Oxygen-free solvents should be used to solubilize peptides containing cysteine, methionine or tryptophan, which are susceptible to rapid oxidation.
3. Allow the peptide to warm to room temperature (preferably in a desiccator) prior to adding the solvent of choice.
4. Solubilization can be improved by warming (<40°C) or sonicating the solution.
5. If the pH of the solution needs to be increased, use only very weak bases to prevent immediate inactivation or racemization.

Guidelines for solubilizing hydrophobic peptides:

1. If the product proves to be insoluble in aqueous buffers due to high hydrophobicity, dissolve a small amount of product in the smallest possible volume of a 50% (v/v) DMSO/water mixture. Then add the desired aqueous solution until the target concentration is achieved.
2. If the product precipitates during this process and cannot be redissolved by adding dimethylsulfoxide (DMSO), then lyophilize the peptide and try again, adding a little more 50% DMSO than in the previous attempt.
3. If DMSO interferes with your experimental system, dimethylformamide (DMF) or acetonitrile can serve as alternate solvents.