How to Calculate the Isoelectric Point of Peptides

••• Comstock Images/Comstock/Getty Images

Peptides are short polymer fragments composed from amino acids. Each peptide has a certain amino acid sequence denoted with a three letter or one letter code; for example the amino acid alanine is abbreviated as “Ala” or “A.” The charge of the peptides in the solution depends upon the solution acidity. The isoelectric point (pI) refers to the solution acidity value at which the peptide molecule has the net charge of zero. The solubility of the peptide is minimal at the isoelectric point. Use available web servers to calculate the pI value for a peptide amino acid sequence.

    Write the peptide sequence using the one-letter code. For example, if a peptide has an amino acid sequence Ala-Ser-Glu-Leu-Pro (Alanine—Serin—Glumatic acid—Leucine—Proline), then the one letter sequence is "ASELP." If necessary consult the three letter to one letter conversion table given in Resources.

    Use any web browser, Internet Explorer or Firefox, for example, to navigate to a server that calculates the peptide isoelectric point (pI); see Resources.

    Enter the peptide one-letter sequence—"ASELP" in our example—in the box, and click on "Compute."

    Read the isoelectric point (pI) value given in the line "Theoretical pI/Mw." In our example, the pI is 4.00. Note the server also calculates the molecular weight (Mw) of the peptide.

Related Articles

How to Calculate the Isoelectric Point
How to Calculate the pH of Ammonia Water Using KB
How to Calculate Moles from Molecular Weight
How to Find the Radius
How to Find the PKA of a Weak Acid
How to Calculate Buffers
Endpoint Math Formula
How to Calculate End Point
How to Calculate Ka From Ph
How to Find Hydroxide Ion Concentration
How to Solve a Parabola
How to Calculate PH of Buffer Solutions
How to Find the X Intercept of a Function
How to Calculate the Formal Charge of CoCl2
How to Read K5M Capacitor Values
How to Calculate Kf
Definition of Molecular Bonds
How to Find a Z Score
How to Determine How Many Hybrid Orbitals

Dont Go!

We Have More Great Sciencing Articles!