( Nucleotides ( ( are ( ( ( heterocyclic compounds ) , ) ( that ( ( is , ) ( they ( contain ( ( ( ( at least ) two ) ( different ( chemical elements ) ) ) ( as ( members ( of ( its rings ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Nucleotides)) (VP (VBP are) (NP (NP (JJ heterocyclic) (NNS compounds)) (, ,) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (, ,) (SBAR (S (NP (PRP they)) (VP (VBP contain) (NP (NP (QP (IN at) (JJS least) (CD two)) (JJ different) (NN chemical) (NNS elements)) (PP (IN as) (NP (NP (NNS members)) (PP (IN of) (NP (PRP$ its) (NNS rings)))))))))))))) (. .)))
Nucleotides are heterocyclic compounds, that is, they contain at least two different chemical elements as members of its rings.
(ROOT (S (NP (DT A) (JJ heterocyclic) (NN compound)) (VP (VBZ contains) (NP (NP (NNS atoms)) (PP (IN of) (NP (NP (QP (CD two) (CC or) (JJR more)) (JJ different) (NNS elements)) (PP (IN in) (NP (PRP$ its) (NN ring) (NN structure))))))) (. .)))