( ( Over ( the ( past ( twenty years ) ) ) ) ( , ( ( this laboratory ) ( ( ( ( has isolated ) and ) ( biochemically ( characterized ( ( four classes ) ( of ( mutants ( -LRB- ( ( reviewed ( in ( -LRB- ( 1 -RRB- ) ) ) ) -RRB- ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Over) (NP (DT the) (JJ past) (CD twenty) (NNS years))) (, ,) (NP (DT this) (NN laboratory)) (VP (VP (VBZ has) (VP (VBN isolated))) (CC and) (VP (ADVP (RB biochemically)) (VBD characterized) (NP (NP (CD four) (NNS classes)) (PP (IN of) (NP (NP (NNS mutants)) (PRN (-LRB- -LRB-) (VP (VBN reviewed) (PP (IN in) (PRN (-LRB- -LRB-) (NP (CD 1)) (-RRB- -RRB-)))) (-RRB- -RRB-))))))) (. .)))
Over the past twenty years, this laboratory has isolated and biochemically characterized four classes of mutants (reviewed in (1)).
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD four) (NNS classes)) (PP (IN of) (NP (JJ biochemical) (NNS compounds))))) (. .)))