Alkaline solution can be added to dissolve the peptides with significant acidity which is difficult to be dissolved, meanwhile acid solution should be added to the Peptides with significant alkalinity which is difficult to be dissolve .

A small amount of organic solvent, such as acetonitrile, DMSO, DMF, propyl alcohol, isopropyl alcohol etc., can be added to the peptides which contains a large number of hydrophobic amino acid or neutral amino acids in the sequences. These peptides are difficult to directly dissolve in water.

When the peptide containing Met or Cys, we can not dissolve it by DMSO. If so, it is likely to lead to the oxidation of -SH.

C term and the N term modification: for acidic peptides, C terminal amidation modification; for Alkaline peptides, N terminal acetylation.

Revision sequence of the peptide chain.: some sequence has a large number of continuous hydrophobic amino acids, such as W, F, V, I, l, m, y, these hydrophobic amino acid sequence at large or continuous repetition and whole peptide usually is insoluble,.In order to enhance the polarity and hydrophilicity of peptide, we also will advise clients to extend sequence or reduce the number of hydrophobic amino acids to increase solubility on the condition of non affecting experimental results.

Replacing hydrophobic amino acid residues of sequences: increasing solubility effect by substituting soluble amino acid for hydrophobic amino acid in sequence.We usually use Gly, Ala to replace the hydrophobic amino acids, which usually gets good dissolving effect.