PredAcc predicts the accessibility to the solvent for amino acids of a protein knowing its sequence.

Accessibility threshold : The relative solvent accessibility value that determines whether a given amino acid is external (solvent accessible) or hidden. An amino acid is declared not exposed to solvent when its observed accessibility is less than a fraction of its accessibility observed in a reference state. Usual values are around 20%. The range available here goes from 0% (totally buried) to 55% (very exposed).

Gamma risk : For some residues, it is possible to warrant that their predicted state is correct given a reduced risk of error, here 5% or 10%. Using such a prediction approach, other residues are predicted as unknown.