Guideline for working with peptides

When working with dissolving peptides following points may help:

• All such attempts should be carried out on very small samples rather than the bulk material.
• Most peptides will dissolve in aqueous media with the addition of a little acid (acetic acid) or a little base (dilute ammonia) depending on their overall charge.
• Before dissolving a peptide short analysis of its sequence might help. If hydrophobic amino acids like A, C, F, I, L, M, P, V, W, Y are consisting more than 50 % of a peptide, dissolve a peptide first in a small amount of either dimethyl sulphoxide (DMSO) or N, N-dimethylformamide (DMF) PRIOR to the addition of any aqueous component.
• Gentle heating or use of ultrasonication may also aid peptide dissolution.

• Peptide should be slowly added to larger volumes of water/buffer, not opposite.
• Problems with peptide solubility can also result from oxidation and the formation of the disulphide bridges. Especially if a peptide has not been stored properly or is rather old. Check this by using Elman's reagent (Pierce).