( It ( ( ( ( was only ) ( in ( the 1950s ) ) ) ( that ( ( cell biologists ) ( ( ( ( put ( ( ( ( ( ( the ( two lines ) ) ( of ( research together ) ) ) , ) ( ( the work ) ( of ( the ( membrane biologists ) ) ) ) ) and ) ( ( the work ) ( of ( the ( structural biologists ) ) ) ) ) ) ( using ( electron microscopy ) ) ) , ) ( to ( form ( ( ( a ( new concept ) ) ( of ( the ( cell membrane ) ) ) ) ( applicable ( to ( all ( biological systems ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBD was) (ADVP (RB only)) (PP (IN in) (NP (DT the) (NNS 1950s))) (SBAR (IN that) (S (NP (NN cell) (NNS biologists)) (VP (VBD put) (NP (NP (NP (DT the) (CD two) (NNS lines)) (PP (IN of) (NP (NP (NN research)) (ADVP (RB together))))) (, ,) (NP (NP (DT the) (NN work)) (PP (IN of) (NP (DT the) (JJ membrane) (NNS biologists)))) (CC and) (NP (NP (DT the) (NN work)) (PP (IN of) (NP (DT the) (JJ structural) (NNS biologists))))) (S (VP (VBG using) (NP (NN electron) (NN microscopy)))) (, ,) (S (VP (TO to) (VP (VB form) (S (NP (NP (DT a) (JJ new) (NN concept)) (PP (IN of) (NP (DT the) (NN cell) (NN membrane)))) (ADJP (JJ applicable) (PP (TO to) (NP (DT all) (JJ biological) (NNS systems)))))))))))) (. .)))
It was only in the 1950s that cell biologists put the two lines of research together, the work of the membrane biologists and the work of the structural biologists using electron microscopy, to form a new concept of the cell membrane applicable to all biological systems.
(ROOT (S (NP (CD Two) (NNS membranes)) (VP (VBP form) (NP (NP (DT the) (NN mitochondrion) (NN structure)) (PP (IN of) (NP (DT a) (NN cell))))) (. .)))