[gmx-users] The last line in a .gro file

[Agnivo Gosai]

Dear Users

The last line of the .gro file lists out three co-ordinates and the GROMACS
manual says that these are the box vectors : v1(x) , v2(y) and v3(z)
Now , before using editconf to place our molecule inside a box , there is
no box associated with the system.
But pdb2gmx generates this .gro file having the vectors listed in the last
line.

My question is :- Is the last line has to do anything with the "size" of
the molecule ?

Thanks & Regards
Agnivo Gosai
Grad Student, Iowa State University.