( Proteins ( ( are ( chains ( of ( ( amino acids ) ( linked together ) ) ) ) ) . ) )
(ROOT (S (NP (NNPS Proteins)) (VP (VBP are) (NP (NP (NNS chains)) (PP (IN of) (NP (NP (JJ amino) (NNS acids)) (VP (VBN linked) (ADVP (RB together))))))) (. .)))
Proteins are chains of amino acids linked together.
(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))))))))) (. .)))