( ( Simulations ( of ( ( ( large molecules ) and ) ( biological macromolecules ) ) ) ) ( ( ( ( can therefore ) only ) ( be ( performed ( with ( classical mechanics ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNS Simulations)) (PP (IN of) (NP (NP (JJ large) (NNS molecules)) (CC and) (NP (JJ biological) (NNS macromolecules))))) (VP (MD can) (ADVP (RB therefore)) (ADVP (RB only)) (VP (VB be) (VP (VBN performed) (PP (IN with) (NP (JJ classical) (NNS mechanics)))))) (. .)))
Simulations of large molecules and biological macromolecules can therefore only be performed with classical mechanics.
(ROOT (S (NP (DT Any) (JJ large) (NN molecule)) (VP (VBZ is) (VP (VBN referred) (PP (TO to) (NP (RB as) (DT a) (NN macromolecule))))) (. .)))