Hi, Justin, At md step, protein run out of box, if it will better that set position constraint, let protein at center of box? Thank you very much! maggin -- View this message in context: http://gromacs.5086.x6.nabble.com/refcoord-scaling-com-tp5009141p5009150.html Sent from the GROMACS Users Forum mailing list archive at Nabble.com.