Please do not hesitate to contact CASLO if you have any questions.
We have collected the following frequently asked questions and the answers:

How do I request a price quotation and order a product?

Please send your request by e-mail. You can also telephone us. You will receive a price quotation within 24 hours, and the price quotation includes detailed instructions for how to order the product. Prices include handling and delivery with express courier.

Are there any countries where peptides cannot be delivered?

CASLO delivers to most countries worldwide. CASLO does not, however, deliver products to personal addresses — only to research institutions, universities, companies, and similar organizations. CASLO only delivers products for research, not for clinical use.

In what format are peptides delivered?

We always deliver peptides in lyophilized format. As standard, we deliver peptides as trifluoroacetate (TFA) salts, where TFA ions counterbalance the positively charged groups on the peptide. We can deliver peptides as chloride or acetate salts, where chloride or acetate ions counterbalance the peptide, but changing the counterion adds an extra charge.

What is the purity of a peptide, and what are the impurities?

We can deliver peptides with purities ranging from >70% up to >99%. Impurities typically consist of peptides missing one or several amino acids. CASLO can help you find the correct purity for your application.

How do I dissolve a peptide?

The solubility of a long peptide strongly depends on the hydrophobicity of the peptide’s amino acid sequence. A peptide longer than 10–15 amino acids is only fully soluble in an aqueous buffer if it contains a certain number of hydrophilic amino acids. You can dissolve hydrophobic peptides in organic solvents like DMSO or similar.

The certificate of analysis, which we deliver with the peptide, specifies a hydrophilic/hydrophobic profile together with detailed guidelines for how to dissolve the peptide. If necessary, CASLO can predict the solubility and give guidelines for how to dissolve a peptide before you order it.

If we predict that the solubility of a peptide is too low for the planned usage, we can add a hydrophilic extension at either the N- or C-terminus to increase the aqueous solubility. CASLO also offers solubility testing of the peptide, and we will then note the solubility in the certificate.

How should I store a peptide?

Store products in lyophilized form at -70°C, or at -20°C if -70°C is not possible, until you use them. We can deliver peptides aliquoted in several vials in quantities that match each application.

What is the shelf life of a peptide?

Peptides remain stable for a minimum of one year if you store them lyophilized in a freezer at -70°C, or at -20°C if -70°C is not possible. Dissolving the peptide will reduce the shelf life. If the peptide contains several reactive amino acids that can oxidize, like Trp, Met, and especially Cys, the shelf life might also decrease.

The peptide contains several cysteines and can therefore easily form disulfide bonds. How do I avoid this?

If the peptide sequence contains several cysteines or other reactive amino acids that oxidize easily, CASLO can deliver the peptide with small amounts of the reductant DTT. We only deliver the peptide with DTT if you order it.

How shall I measure a peptide concentration?

The certificate of analysis, which we deliver together with the peptide, lists the theoretical molar weight (M.W.) and the M.W. detected by mass spectrometry for the peptide without counterions. In practice, however, a peptide is a salt where counterions counterbalance the positive loadings in the peptide. CASLO always delivers detailed instructions for how to calculate the theoretical M.W., including counterions.

Can I use peptides for cell cultures?

We generally deliver peptides as trifluoroacetate (TFA) salts. You can use peptide TFA salts for most cell cultures. Some cell cultures, however, are sensitive to the TFA counterion.

For use with these cell cultures, CASLO recommends delivering peptides as chloride or acetate salts, which are natural counterions. Peptides are generally not completely sterile, even though lyophilization has some sterilization effect. You can sterile filtrate peptides using standard sterile filters.

How can I make my peptide permeable to cells?

Several cell penetrating amino acid sequences exist, and most of them are positively loaded sequences. We can prolong peptide synthesis with a cell penetrating sequence. The most commonly used cell penetrating sequence is the HIV-TAT sequence (YGRKKRRQRRR), which we prolong to the N-terminal part of a peptide.

Another way is to conjugate fatty acids to the peptide (for example, myristic acid). The fatty acid places itself into the fatty acyl core of the phospholipid bilayer of the membrane on eukaryotic cells, acting as a lipid anchor in the biomembrane.

How can I make peptides resistant to degradation in the cells?

Cells contain several enzymes that degrade peptides and proteins. You can make peptides more resistant by ordering them with an acetylated N-terminus and amidated C-terminus. We offer these modifications without extra charge. We can also make peptides with the D-isomeric form of one or several amino acids in the sequence, which also increases the stability of the peptide.