[Chimera-users] Question about Model Loops Option in Chimera

Hello, I have a protein crystal structure where some regions are not resolved in the crystal. Therefore, I want to predict and fill these regions, without touching the rest, by using the Model Loops/Refine Structure option of Modeller in Chimera. When I select the non-terminal missing structure as a model and standard as a loop modeling protocol, some atoms in the rest of the structure are shifted from the original positions. However, I want to keep them as they are. Here I would like to ask what standard loop modeling protocol corresponds to. Does it also refine or optimize the structure as a whole? What does it actually correspond to? Any help would be appreciated. Thanks. Ece