Thanks a lot for trying to help. I did exactly just that, the option you described renames duplicate chains in the structure, however, in my structure, there are no duplicate chains. There's an A and a B chain. When I copy combine, I get another structure with A and B as well. I want the second structure to have C and D instead, i.e. a unique chain ID that is different from the original model's chain.

On Thu, Apr 19, 2018 at 6:43 PM, Elaine Meng <meng@cgl.ucsf.edu> wrote:

Hi Ahmad,
See the previous reply: the combined single model will not have any two chains with the same ID if you use the option I described, which is the default. Make sure you are looking only at the final combined model, not the other starting models which may still be open.

Elaine

> On Apr 19, 2018, at 12:40 PM, Ahmad Abdelzaher <underoath006@gmail.com> wrote:
>
> Sorry for the confusion. By tubulin monomer I mean an alpha-beta dimer. A tubulin trimer would be three tubulins of six chains A-B-A-B-A-B, each two belonging to a tubulin monomer.
>
> My question is, if the first monomer has chains A and B, I want the copy/combine model to have different chain ID letters from A and B, for example C and D, and so on for the third, and fourth, etc.
>
> How can I do that?
>
> Regards.