I want to generate the system between short protein and membrane LIPID21 forcefield

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GROMACS version: 2021.5
GROMACS modification: No
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I’m a beginner in this field. I would like to set up the system of membrane using Lipid21 force field and peptide to see their aggregation.
First, I simulate separately for A) pure membrane (LIPID21) generated by CHARMM-GUI and B) pure peptide (amber99sb-ildn). Both simulation run without problem.

Second, I have tried to put A) and B) together. I use .top from both simulation that I have tried but it doesn’t work.
This is the error:

Fatal error:
Syntax error - File POPC.itp, line 11
Last line read:
‘[ moleculetype ]’
Invalid order for directive moleculetype
…

:::After posted:::
I have tried more to change the order of .itp files in .top file, the error was changed.
ERROR 1 [file POPC.itp, line 17]:
Atomtype cD not found

I go to check in POPC.itp but I still found cD atomtype. I don’t know where should I continue after this.
Would you give me suggestion?

2

See No default Improper Dih. types - #2 by MagnusL. You will need to copy and paste a bit between files to make sure that all definitions are in the right order.