Dissolving Charged Peptides

  1. A peptide is acidic if the overall net charge of the peptide is negative. For an acidic peptide, if the total number of charges of the peptide at pH 7 is greater than 25% of the total number of residues, add a small amount of 0.1M ammonium bicarbonate to dissolve the peptide and dilute it with water to the desired concentration. Make certain that the resulting pH of the peptide solution is about 7 and adjust the pH as needed.
  2. A peptide is basic if the overall net charge of the peptide is positive. For a basic peptide, if the total number of charges of the peptide at pH 7 is between 10-25% of the total number of residues, add a small amount of 25% acetic acid to dissolve the peptide and dilute it with water to the desired concentration.
  3. A peptide is considered neutral if the overall net charge of the peptide is zero. If the total number of charges is greater than 25% of the total number of residues, use the strategy described in section 1. If the total number of charges is between 10-25% of the total number of residues, use organic solvents as recommended elsewhere in this document.
  4. If the total number of charges of a peptide is less than 10% of the total number of residues, use of organic solvents is recommended.