( ( ( The iron ) ( in hemoglobin ) ) ( , ( however ( , ( ( ( is not ) ferromagnetic ) . ) ) ) ) )
(ROOT (S (NP (NP (DT The) (NN iron)) (PP (IN in) (NP (NN hemoglobin)))) (, ,) (ADVP (RB however)) (, ,) (VP (VBZ is) (RB not) (ADJP (JJ ferromagnetic))) (. .)))
The iron in hemoglobin, however, is not ferromagnetic.
(ROOT (S (NP (NNP Iron) (NNS ions)) (VP (VBP are) (ADJP (JJ critical) (PP (IN for) (NP (NP (DT the) (NN formation)) (PP (IN of) (NP (NN hemoglobin))))))) (. .)))