( Sarcomeres ( ( are ( ( the ( smallest ( contractile units ) ) ) ( of ( muscle fiber ) ) ) ) . ) )
(ROOT (S (NP (NNS Sarcomeres)) (VP (VBP are) (NP (NP (DT the) (JJS smallest) (NN contractile) (NNS units)) (PP (IN of) (NP (NN muscle) (NN fiber))))) (. .)))
Sarcomeres are the smallest contractile units of muscle fiber.
(ROOT (S (NP (DT A) (NN sarcomere)) (VP (VBZ is) (NP (NP (DT the) (JJS smallest) (NN contractile) (NN portion)) (PP (IN of) (NP (DT a) (NN muscle))))) (. .)))