Hi Teddy,
Matchmaker does “rigid body” fitting and therefore naturally produces the ‘B’ result. Perhaps you actually meant to ask if it could produce the ‘A’ result. If so, it can — but not by using Matchmaker alone. The general procedure for that would be:
1) Open two copies of the linear form, and match them to opposite sides of the looped form, probably by using Matchmaker while restricting matching to the current selection and selecting one side, then the other.
2) Delete one half of one linear form (select the part to delete and Actions->Atoms/Bond->delete) and the other half of the other form.
3) Use the Model Panel’s “combine” button to combine the two halves into one model.
4) Use the “bond” command to form a (very long) bond connecting the two halves, between atoms that normally are connected.
5) Use Tools->Structure Editing->Minimize Structure to minimize the loop portion while holding the atoms in the matched parts frozen.
—Eric
Eric Pettersen
UCSF Computer Graphics Lab