Dear ChimeraX Support Team, I am currently using ChimeraX (v1.10.1) to study whether certain amino acid residues are surface-exposed or buried in my protein structures (WT and mutants from AlphaFold/NeuroSnap). To assess this, I measured solvent accessible surface area (SASA) with the following commands: measure sasa #1 measure sasa #1:92 measure sasa #1:562 This gives me the following SASA values (in Ų): * WT Ala92: 216.4 Ų * WT Gly562: 189.0 Ų When I compare these to published maximum ASA (MaxASA) values from Tien et al. 2013 (probe radius 1.4 Å): * Ala (max ASA) = 129 Ų * Gly (max ASA) = 104 Ų I get relative solvent accessibility (RSA) values greater than 1: * Ala92: 216.4 / 129 = 1.68 * Gly562: 189.0 / 104 = 1.82 Since RSA should not exceed 1, I believe I am mismatching ChimeraX’s calculation settings with the MaxASA reference set. So my questions are: 1. What radii model and probe radius does measure sasa in ChimeraX use by default? 2. Is there a way in ChimeraX to directly assign per-residue SASA attributes and normalize them internally (so RSA values remain ≤1)? 3. If ChimeraX defaults differ from published MaxASA tables, would you recommend reporting only SASA values, or generating my own MaxASA reference values with ChimeraX for consistency? I would be very grateful for any guidance or documentation pointers so I can report values in a way that is consistent and interpretable. Best, Kazi Sayeeda PhD Candidate Dept. of Cell and Developmental Biology (Krendel Lab) SUNY Upstate Medical University Syracuse, NY 13210 sayeedak@upstate.edu<mailto:%20sayeedak@upstate.edu>