Hi, I am trying to work out how maps are handled in various graphics programs so I can easily move between programs and expect to see the same thing in each session. Unfortunately at the moment that isn't working so well, and I would like to resolve this issue. Basically I have a situation where I have a PDB model and a CCP4 format EM density map in Chimera that are docked. When I open the exact same map and model in other programs such as O or Pymol, the map and the model are no longer in agreement. What I have noticed is that if I draw the unit cell for the map (P1 symmetry since this is an EM reconstruction), in Chimera, the model and map live in the center of the unit cell and are docked. If I draw the unit cell for O or Pymol, the map lives at the origin of the unit cell, at (0,0,0), which is in the corner, and model is outside of the unit cell offset by what appears to be some arbitrary translation (I have tried using half the unit cell dimensions as a translation, but that unfortunately gets me _very_ close to being correctly docked in the map, but off by some 10A). It appears Chimera is handling the map and model differently than the other packages and I am trying to get an idea of what happens when this map is loaded. I am including a listing of the map header from MAPMAN below. Thanks! Albion Grid = 96 96 96 Origin = -48 -48 -48 Extent = 96 96 96 Cell = 213.423 213.423 213.423 90.000 90.000 90.000 UVW = 1 2 3 Spcgrp = 1 Nr of points = 884736 Density min = -6.915E-01 Max = 2.397E+00 Average = 7.247E-11 Sigma = 2.290E-01 Variance = 5.243E-02 Mappage Prod= 8.257E+01 Plus = 57 Dyn. range = -6.903E-01 To = 2.398E+00 Cell vol. = 9.721E+06 Voxel vol. = 1.099E+01 Grid vol. = 9.721E+06 %Cell vol. = 100.00 Origin frac = -0.50000 -0.50000 -0.50000 Origin Cart = -106.712 -106.712 -106.712 Top frac = 0.48958 0.48958 0.48958 Top Cart = 104.488 104.488 104.488 Spacing = 2.223 2.223 2.223 Top = 47 47 47 Changes = F