Gurpreet Singh wrote: > Dear Gromacs Users, > > I am using g_sas program of gromacs to calculate SASA, ?using -pbc flag. > It seems to me that the program does not take into account the periodic > boundary conditions. > Even thought this problem is mentioned in the mailing list, it still not > clear whether the program can or cannot take into account the > periodicity. > i am using gromacs3.3.2 . Could anyone please clarify this. > http://bugzilla.gromacs.org/show_bug.cgi?id=180 I downloaded the gromacs 3.3.3 and carried out some test calculations. The PBC is still not working, at least with test i have performed. I generated a trajcetory file containing two atoms in a cubic box of 4nm having same x and y coordinates and varied the z coordinates of one of the atoms. one atom is fixed at z coordinate of 3.9. The result of sasa vs coordinates is as follows: Step no z coordinate total_sasa 1 2.05000000074506 14.1497 2 2.10000000149012 14.1497 3 2.15000000223517 14.1497 4 2.20000000298023 14.1497 5 2.25000000372529 14.1497 6 2.30000000447035 14.1497 7 2.35000000521541 14.1497 8 2.40000000596046 14.1497 9 2.45000000670552 14.1497 10 2.50000000745058 14.1497 11 2.55000000819564 14.1497 12 2.60000000894070 14.1497 13 2.65000000968575 14.1497 14 2.70000001043081 14.1497 15 2.75000001117587 14.1497 16 2.80000001192093 14.1497 17 2.85000001266599 14.1497 18 2.90000001341105 14.1497 19 2.95000001415610 14.1497 20 3.00000001490116 14.1497 21 3.05000001564622 14.1497 22 3.10000001639128 14.1497 23 3.15000001713634 14.1497 24 3.20000001788139 14.1497 25 3.25000001862645 14.1497 26 3.30000001937151 14.1497 27 3.35000002011657 13.7971 28 3.40000002086163 13.1359 29 3.45000002160668 12.5849 30 3.50000002235174 11.9237 31 3.55000002309680 11.3727 32 3.60000002384186 10.7115 33 3.65000002458692 10.1605 34 3.70000002533197 9.49926 35 3.75000002607703 8.94826 36 3.80000002682209 8.39726 37 3.85000002756715 7.51566 38 3.90000002831221 14.1497 39 3.95000002905726 7.51566 40 2.980232238769531E-008 14.1497 41 5.000003054738045E-002 14.1497 42 0.100000031292439 14.1497 43 0.150000032037497 14.1497 44 0.200000032782555 14.1497 45 0.250000033527613 14.1497 46 0.300000034272671 14.1497 47 0.350000035017729 14.1497 48 0.400000035762787 14.1497 49 0.450000036507845 14.1497 50 0.500000037252903 14.1497 51 0.550000037997961 14.1497 52 0.600000038743019 14.1497 53 0.650000039488077 14.1497 54 0.700000040233135 14.1497 55 0.750000040978193 14.1497
I used the following command to calculate the sasa g_sas_d -f test.xtc -s topol.tpr -pbc -ndots 500 I can attached the tpr and xtc file if needed With Regards, Gurpreet singh
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