( Proteins ( ( are ( chains ( of ( amino acids ) ) ) ) . ) )
(ROOT (S (NP (NNPS Proteins)) (VP (VBP are) (NP (NP (NNS chains)) (PP (IN of) (NP (JJ amino) (NNS acids))))) (. .)))
Proteins are chains of amino acids.
(ROOT (S (NP (DT A) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN protein)) (VP (VBZ is) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (JJ amino) (NNS acids)) (VP (VBP are) (VP (VBN linked) (ADVP (RB together)) (PP (IN in) (NP (DT a) (JJ long) (NN chain))))))))) (. .)))