PEA Calculator

Method

The Percent Epitope Accessibility (PEA) Calculator uses solvent-accessible surface area (SASA) data obtained from the .rsa file generated by the NACCESS tool.

For each residue in the protein, the relative accessibility is calculated based on the residue's solvent-exposed surface area compared to the maximum possible exposure. This value is then normalized and used to identify regions (epitopes) with accessibility values above a defined threshold (25%).

The calculation steps are as follows:

  1. Normalize accessibility values for each residue.
  2. Identify residues with accessibility above 25%.
  3. Calculate accessibility percentages for specified epitopes based on selected residue ranges.
  4. Compute the Percent Epitope Accessibility (PEA) by dividing the number of accessible residues in epitopes by the total accessible residues and multiplying by 100.

This approach aids in identifying exposed regions on the protein surface that could potentially serve as epitopes for immune recognition.

The formula used for PEA Calculation is:

P E A = Total count of accessible residues in Epitope Regions Total count of accessible residues in Sequence × 100