I want to use GROMACS 2018.8 to simulate pulling a 28-bp DNA G-quadruplex structure and calculate the free energy profile with the enhanced sampling method(AWH) during the pulling process.The reaction coordinates are the 5' prime and 3' prime atoms along the two ends of the G-quadruplex . how to set the parameters of AWH ? Could someone provide a example of md.mdp for me ? Thank you very much.