Relative accessible surface area or relative solvent accessibility (RSA) of a protein residue is a measure of residue solvent exposure.
This discrepancy can be traced back to the conformation in which the Gly-X-Gly tripeptides are evaluated to calculate MaxASA.
The largest ASA values are consistently observed in alpha helices, with backbone angles around
Tien et al. 2013 recommend to use their theoretical MaxASA values (2nd column in Table), as they were obtained from a systematic enumeration of all possible conformations and likely represent a true upper bound to observable ASA.
[1] ASA and hence RSA values are generally calculated from a protein structure, for example with the software DSSP.
[4] However, there is also an extensive literature attempting to predict RSA values from sequence data, using machine-learning approaches.
[5] [6] Experimentally predicting RSA is an expensive and time-consuming task.
In recent decades, several computational methods have been introduced for RSA prediction.