It has been a difficult problem for peptide workers to dissolve synthetic peptides with the solvent. According to the different amino acid sequences, we can use the following methods to dissolve synthetic peptides. It is best to dissolve a small amount of peptide water solution, do not dissolve all the samples at once.

1 the value of acidic amino acid Asp (D), Glu (E) and C end -COOH was set to -1.

2 the basic amino acid Arg (R), Lys (K), His (H) value of +1.

3 calculate the total charge in the peptide.

4 if the total charge of the peptide is positive, the peptide is alkaline and can be dissolved by water. If the peptide is insoluble in water, it can be dissolved with 10% acetic acid or higher concentration of acetic acid. If the peptide is insoluble, add TFA (<50ml) to dissolve, and dilute with deionized water to 1ml.

5 if the total charge of the peptide is negative, the peptide is acidic and can be dissolved in water. If the peptide is insoluble in water, add NH4OH (<50ml) to dissolve, and dilute with deionized water to 1ml.

6 if the total charge of the peptide is 0, the peptide is neutral. Neutral peptides need to be dissolved in organic solvents such as acetonitrile, methanol, isopropyl alcohol, and can also be modified with denaturing agents (e.g. urea, guanidine hydrochloride, etc.).

Example: KRLMKSIEVIMPL: (+4) + (-2) = +2. This peptide is alkaline. See Step 4 above.

LVKMKSIEDPDCE: (+3) + (-5) = -2. This peptide is acidic. See Step 5 above.