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I'm new to gmx so I'm just seeing if I'm able to make homoblock polypeptides. I would like to simulate a 5 residue polyglycine. I've used PRODRG to generate the pdb file, however trying to convert the file with pdb2gmx I receive the error:<br><br>Fatal error:<br>Residue 'Y' not found in residue topology database<br><br>My pdb file is:<br><br><br>ATOM 1 O GLY 1 -2.600 -2.350 -0.400 1.00 20.00 O<br>ATOM 2 C GLY 1 -2.250 -1.400 0.340 1.00 20.00 C<br>ATOM 3 O GLY 1 -1.850 -1.490 1.520 1.00 20.00 O<br>ATOM 4 CA GLY 1 -2.330 0.010 -0.240 1.00 20.00 C<br>ATOM 5 N GLY 1 -3.620 0.630 0.130 1.00 20.00 N<br>ATOM 6 C GLY 2 -3.800 1.640 1.000 1.00 20.00 C<br>ATOM 7 O GLY 2 -4.910 2.110 1.230 1.00 20.00 O<br>ATOM 8 CA GLY 2 -2.600 2.240 1.730 1.00 20.00 C<br>ATOM 9 N GLY 2 -2.160 3.460 1.030 1.00 20.00 N<br>ATOM 10 C GLY 3 -2.510 4.720 1.320 1.00 20.00 C<br>ATOM 11 O GLY 3 -2.050 5.670 0.680 1.00 20.00 O<br>ATOM 12 CA GLY 3 -3.510 4.990 2.460 1.00 20.00 C<br>ATOM 13 N GLY 3 -4.640 5.790 1.950 1.00 20.00 N<br>ATOM 14 C GLY 4 -5.930 5.680 2.300 1.00 20.00 C<br>ATOM 15 O GLY 4 -6.800 6.390 1.810 1.00 20.00 O<br>ATOM 16 CA GLY 4 -6.340 4.640 3.360 1.00 20.00 C<br>ATOM 17 N GLY 4 -6.800 5.360 4.570 1.00 20.00 N<br>ATOM 18 C GLY 5 -7.330 4.810 5.670 1.00 20.00 C<br>ATOM 19 O GLY 5 -7.640 5.500 6.640 1.00 20.00 O<br>ATOM 20 CA GLY 5 -7.550 3.300 5.730 1.00 20.00 C<br>ATOM 21 N GLY 5 -8.990 3.000 5.660 1.00 20.00 N<br>END<br><br>I'm not sure what I could be doing wrong since I pretty much mimicked the speptide.pdb in the tutor file.<br><br>Thanks for the help,<br>Joe.<br>                                            </body>
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