( ( A protein ) ( ( is ( ( a chain ) ( of ( amino acids ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN protein)) (VP (VBZ is) (NP (NP (DT a) (NN chain)) (PP (IN of) (NP (JJ amino) (NNS acids))))) (. .)))
A protein is a chain 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))))))))) (. .)))