Yun He wrote: > I have read some interesting threads about how to build a multi-chain model, > but these questions are usually focused on building from templates with the > same number of chains. Here is my question, how could I build a tetramer from > a dimer, if any chain of this tetramer is similar to the chain of that dimer.

If you only have a dimer, then Modeller cannot build a tetramer model, since it doesn't have any information on how the chains interact with each other. Modeller is not a docking program - you would need to dock your two dimers together first to make a tetramer. Alternatively, you could add manual distance restraints to your system to try and pull the chains together in the right way, but it would be tricky to do correctly.

Ben Webb, Modeller Caretaker