Peptide Storage and Handling

Storage Of Lyophilised Peptides

All products should be stored desiccated and refrigerated (preferably at -20°C). Most peptides stored in this way will remain stable for several years.

Storage of Peptides In Solution

Peptides in solution are much less stable than in the lyophilised form. Solutions should be made up at neutral pH (pH 5-7) and stored frozen at -20°C. To avoid repeated thawing and refreezing of the sample it is recommended that the peptide stock solution be divided into aliquots. Any portion of an aliquot unused after thawing should be discarded.

Reconstitution and Handling of Peptides

Most peptides will be soluble in sterile, distilled or MilliQ water. When first solubilising the peptide care should be taken to ensure that the initial concentration is greater than the desired final concentration. This will allow for the addition of other solubilising agents should the peptide prove to have only limited solubility.

If the peptide exhibits only limited solubility in water, then several options are open to aid this process, such as the addition of:

1. Dilute acetic acid (0.1M) for basic peptides (containing Arg, Lys, His).

2. Dilute ammonia (0.1M) for acidic peptides (containing Asp, Glu).

3. 10% organic modifier (i.e. Ethanol) for very hydrophobic peptides.

4. DMSO for extremely insoluble peptides (see note).

5. Concentrated solutions of either guanidine hydrochloride or urea may also be useful.

In conjunction with the options outlined above, sonication can also be a useful aid for solubilising peptides.

NOTE: The use of organics such as Ethanol, DMSO etc. may interfere with some biological assays. The use of DMSO should be avoided if the peptide contains methionine residues as this solvent may oxidise the Met to Met oxide (MetO).

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