( proteins ( ( are ( ( long chains ) ( of ( amino acids ) ) ) ) . ) )
(ROOT (S (NP (NNS proteins)) (VP (VBP are) (NP (NP (JJ long) (NNS chains)) (PP (IN of) (NP (JJ amino) (NNS acids))))) (. .)))
proteins are long chains of amino acids.
(ROOT (S (NP (NNPS Proteins)) (VP (VBP are) (NP (NP (JJ long) (NNS chains)) (PP (IN of) (NP (JJ amino) (NNS acids))))) (. .)))