1. What is Peptide Net Charge?

The net charge of a peptide is the sum of all positive charges minus the sum of all negative charges at a given pH. It's important for understanding peptide solubility, interactions, and behavior in different environments.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

• Positive Charges come from:
  • N-terminus (when pH < 9.0)
  • Lysine (K) side chains
  • Arginine (R) side chains
  • Histidine (H) side chains
• Negative Charges come from:
  • C-terminus (when pH > 2.0)
  • Aspartic acid (D) side chains
  • Glutamic acid (E) side chains
  • Cysteine (C) when pH < 8.4
  • Tyrosine (Y) when pH < 10.5

3. Importance of Net Charge Calculation

Details: Knowing the net charge helps predict peptide solubility, behavior in electrophoresis, interaction with other molecules, and suitability for various applications in biochemistry and medicine.

4. Using the Calculator

Tips: Enter the peptide sequence using one-letter amino acid codes (e.g., "ACDEFGHIKLMNPQRSTVWY"). The pH should be between 0 and 14.

5. Frequently Asked Questions (FAQ)

Q1: Why does net charge change with pH?
A: Different amino acid side chains protonate/deprotonate at different pH values, changing their charge state.

Q2: What is the isoelectric point (pI)?
A: The pH at which the peptide has a net charge of zero. This calculator can help estimate pI by testing different pH values.

Q3: How accurate is this calculator?
A: It provides a good estimate but doesn't account for neighboring group effects or 3D structure influences on pKa values.

Q4: What about modified amino acids?
A: This calculator handles standard amino acids only. Modified residues require special consideration.

Q5: Why is net charge important in Australia?
A: Australian researchers frequently study peptides for drug development, biotechnology, and native animal/plant research where charge properties are crucial.