( ( ( ( ( Tyrosine ( Crystals Tyrosine ) ) , ) ( an ( amino acid ) ) ) , ) ( ( may ( be ( the problem ) ) ) . ) )
(ROOT (S (NP (NP (NNP Tyrosine) (NNPS Crystals) (NNP Tyrosine)) (, ,) (NP (DT an) (JJ amino) (NN acid)) (, ,)) (VP (MD may) (VP (VB be) (NP (DT the) (NN problem)))) (. .)))
Tyrosine Crystals Tyrosine, an amino acid, may be the problem.
(ROOT (S (NP (NNS Catecholamines)) (VP (VBP are) (NP (NP (DT a) (NN class)) (PP (IN of) (NP (JJ amine) (NNS hormones))) (SBAR (WHNP (WHNP (DT that)) (NP (WRB when) (JJ synthesised))) (S (VP (VBP form) (NP (DT the) (JJ amino) (NN acid) (NN tyrosine))))))) (. .)))