( ( At ( the center ) ) ( ( ( ( is ( the nucleus ) ) , ) ( containing ( ( protons and ) neutrons ) ) ) . ) )
(ROOT (SINV (PP (IN At) (NP (DT the) (NN center))) (VP (VBZ is)) (NP (DT the) (NN nucleus)) (, ,) (S (VP (VBG containing) (NP (NNS protons) (CC and) (NNS neutrons)))) (. .)))
At the center is the nucleus, containing protons and neutrons.
(ROOT (S (NP (NNS Protons) (CC and) (NNS neutrons)) (VP (VBP are) (VP (VBN located) (PP (IN in) (NP (DT the) (JJ central) (NN nucleus))))) (. .)))