Friends, I have a task to calculate how much is the buried SASA during formation of a bi-domain protein. The usual relation to obtain is (SAS-domain1 + SAS-domain2) - SAS-complete I have a difficulty to understand how the calculation is performed in Chimera. As a test case, i used the 1crn.pdb and performed using MSMS and in Chimera. *MSMS calculation* (Input: msms -if 1crn.xyzr -probe_radius 1.5 -density 3.0) Complete system SAS = 3054.258 , (residue 1-23) pA = 2143.122 , (residue 24-46) pB = 2324.809, hence total buried = ( pA + pB) - 3054.258 = 1413.673 *Chimer calculation* surf #0 (Reply log: SAS = 3022.61) measure buriedArea :1-23 :24-46 probeRadius 1.5 vertexDensity 3.0 Status line : SAS = 697.876, SES = 423.938 Reply log: *Buried solvent accessible surface area* B1SAS = 681.191, B2SAS = 714.56, BaveSAS = 697.876 (A1 = 2116.11, A2 = 2302.43, A12 = 3022.79 = 1434.92 + 1587.86) I am not getting the calculation (and the motive as well) of the BaveSAS in the following part of the code. q1) What is Chimera actually doing here q2) Which one i should report, raw buried SAS or BaveSAS in your opinion ? ---------------------------------- for ai,a in enumerate(atoms1): a.buriedSESArea = aareas1[ai,0] - aareas12[ai,0] a.buriedSASArea = aareas1[ai,1] - aareas12[ai,1] ases121 += aareas12[ai,0] asas121 += aareas12[ai,1] for ai,a in enumerate(atoms2): a.buriedSESArea = aareas2[ai,0] - aareas12[n1+ai,0] a.buriedSASArea = aareas2[ai,1] - aareas12[n1+ai,1] ases122 += aareas12[n1+ai,0] asas122 += aareas12[n1+ai,1] careas1, careas2, careas12 = s1[4], s2[4], s12[4] ases1, asas1 = area_sums(careas1) ases2, asas2 = area_sums(careas2) ases12, asas12 = area_sums(careas12) bsas1 = asas1 - asas121 bsas2 = asas2 - asas122 bsas = 0.5 * (bsas1 + bsas2) bses1 = ases1 - ases121 bses2 = ases2 - ases122 bses = 0.5 * (bses1 + bses2) Thanks, Bala -- C. Balasubramanian -- C. Balasubramanian