Dear Chimera-users, Hello, I am a brand new entry into this forum. I have started using chimera recently. I use Gromacs for my molecular modeling work. Till I become friendly with chimera I need your valuable suggestions and cooperations. I request you to kindly bear with my very silly doubts and questions. Let me explain my problem. I have a protein of 35 residues and have simulated in a box of water for 10ns. My protein has charge so in order to neutralize it I have added counterions randomly placed them in the solvent(water). The counter ions that I am adding are Cl- ions. I have created a *.trr file of the tracjectory for this 10ns. I would like to visulaize this trajectory using chimera. I am using Tools /MD/Ensemble Analysis /MD Movie to load the trr file. when I do so I am getting the following error: Unknown molecule type: CL- TypeError: __len__() should return an int (see reply log for Python traceback info) Traceback (most recent call last): File "/usr/local/chimera/share/__main__.py", line 59, in ? value = chimeraInit.init(sys.argv) File "CHIMERA/share/chimeraInit.py", line 318, in init tkgui.eventLoop() File "CHIMERA/share/chimera/tkgui.py", line 2675, in eventLoop File "CHIMERA/lib/python2.4/lib-tk/Tkinter.py", line 965, in mainloop self.tk.mainloop(n) File "CHIMERA/lib/python2.4/site-packages/Pmw/Pmw_1_2/lib/PmwBase.py", line 1751, in __call__ File "CHIMERA/lib/python2.4/site-packages/Pmw/Pmw_1_2/lib/PmwBase.py", line 1814, in _reporterror File "CHIMERA/lib/python2.4/site-packages/Pmw/Pmw_1_2/lib/PmwBase.py", line 1377, in displayerror File "CHIMERA/lib/python2.4/site-packages/Pmw/Pmw_1_2/lib/PmwBase.py", line 1747, in __call__ File "CHIMERA/share/chimera/baseDialog.py", line 231, in <lambda> File "CHIMERA/share/chimera/baseDialog.py", line 473, in OK File "CHIMERA/share/Trajectory/EnsembleLoader.py", line 87, in Apply File "CHIMERA/share/Trajectory/formats/Gromacs/__init__.py", line 56, in loadEnsemble File "CHIMERA/share/Trajectory/formats/Gromacs/__init__.py", line 67, in loadEnsemble File "CHIMERA/share/Trajectory/formats/Gromacs/Gromacs.py", line 30, in __init__ File "CHIMERA/share/Trajectory/formats/Gromacs/Gromacs.py", line 218, in __init__ File "CHIMERA/share/Trajectory/formats/Gromacs/Gromacs.py", line 229, in _readHeader File "CHIMERA/lib/python2.4/xdrlib.py", line 194, in unpack_fstring if j > len(self.__buf): TypeError: __len__() should return an int What exactly is the problem ? How to solve it ?