How to Calculate the Isoelectric Point

Without Protein Sequence

• 1

  Decide how to obtain the protein sequence. If the sequence is already available, go directly to Section 2. Otherwise, obtain it from the Universal Protein Resource database (see Resources).

• 2

  Enter a protein name as keywords in the query field and click "Search."

• 3

  Scroll down the search results and find an appropriate entry. Write down the database accession number.

• 4

  Navigate to the ExPASy Server Computing Tool (see Resources).

• 5

  Enter the database accession number from Step 4 in the field and "Click here to compute pI/Mw."

• 6

  Click "Submit" on the next screen.

• 7

  Read the isoelectric point (pI) value.

With Protein Sequence

• 8

  If the sequence was already available, navigate to the ExPASy Server Computing Tool (see Resources).

• 9

  Enter the sequence manually in the field or copy and paste from a file. Click "Click here to compute pI/Mw."

• 10

  Read the isoelectric point (pI) value.