Penetrating Peptides

Cupid Peptides are purified in our lab using the experience and knowledge we have gained since the company was formed.

Cupid Peptides arrive in a liquid in packs of 1 UNIT. They are designed to be used straight out of the packaging with minimal fuss. They do not contain TFA or Acetate so do not require lengthy clean-up steps. The only step before adding to cultured cells involves making certain the peptide is dissolved thoroughly in water.

Cupid Peptides are shipped as a 100 uM Stock Solution in distilled water. Upon arrival the stock solution should be aliquoted as desired and frozen at -20 degrees. I can then be thawed, used in an experiment and refrozen many times. It is not recommended to store peptide after it has been diluted in media or buffer.

Vacuum Sealed Cupid peptides

Cupid peptides are supplied in quantities of 1 Unit, where 1 Unit is 10 nanomoles of peptide. When fully dissolved in 100 microlitres of distilled water, 1 Unit will create a 100 micromolar Stock Solution. This Stock Solution is then diluted in the normal buffer the cells are in, to the dose required in the experiment. We recommend exposing cells to a top dose of 5 uM and titrating down from there.

We determine the concentration of all Cupid peptides using a commercial bicinchoninic acid (BCA) protein assay, using Bovine Serum Albumin (BSA) to generate a standard curve at an absorbance of 562 nanometers vs a water blank. Based on this curve, the peptide molarity is then calculated using the theoretical molecular weight of each Cupid Peptide (determined using protein programs available online such as:

Guarantees of Cupid Peptides

We provide Cupid peptides to the customer with essential guarantees that we know are important for their use with cultures of living cells.


1. Solubility* The peptides are soluble in water to at least 200 micromolar concentration (x40 recommended maximum dose).

2. Purity** The purity of the peptide is in excess of 80% unless otherwise stated.

3. Sterility. All products have been passed through a 0.22 micron filter


*The peptide solution remains soluble when diluted to 5 micromolar with common media formulations or 20 mM phosphate buffer or PBS (137 mM NaCl) at pH 7-8.

**The identity and purity of peptides are confirmed by running peptide samples on SDS-PAGE gels followed by protein staining to confirm the major peptide band agrees with the molecular weight calculated for the Cupid peptideand assess for the presence of any other bands. Note: Any protein impurities do not possess the Cupid cell-permeating sequence and do not have the capability to penetrate living cells. The Cupid Control Peptide is available to control against any bioactivity of any protein impurities