( ( ( ( ( ( ( ( CO 2 ) and ) ( H 2 ) ) ( ( O usually ) ( ( act ( as poisons ) ) ( to ( ( alkali ( metal ( methoxide catalyst ) ) ) ( in ( the ( low-temperature ( MeOH ( synthesis reaction ) ) ) ) ) ) ) ) ) ) , ) yet ) ( they ( play ( ( a ( promotional role ) ) ( in ( this ( new route ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (NNP CO) (CD 2)) (CC and) (NP (NNP H) (CD 2))) (VP (VBP O) (ADVP (RB usually)) (VP (VB act) (PP (IN as) (NP (NNS poisons))) (PP (TO to) (NP (NP (JJ alkali) (NN metal) (NN methoxide) (NN catalyst)) (PP (IN in) (NP (DT the) (JJ low-temperature) (NNP MeOH) (NN synthesis) (NN reaction)))))))) (, ,) (CC yet) (S (NP (PRP they)) (VP (VBP play) (NP (NP (DT a) (JJ promotional) (NN role)) (PP (IN in) (NP (DT this) (JJ new) (NN route)))))) (. .)))
CO 2 and H 2 O usually act as poisons to alkali metal methoxide catalyst in the low-temperature MeOH synthesis reaction, yet they play a promotional role in this new route.
(ROOT (S (PP (IN In) (NP (DT a) (JJ biological) (NN reaction))) (, ,) (NP (NNS proteins)) (VP (VBP act) (PP (IN as) (NP (NNS catalysts)))) (. .)))