( ( The ( `` ( Brownian ( Ratchet ( '' model ) ) ) ) ) ( ( states ( that ( ( a ( protrusive force ) ) ( is ( ( exerted ( during ( polymerization ( of actin ) ) ) ) ( by ( utilising ( ( the energy ) ( of ( ( ( Brownian motion ) ( ( in which ) ( ( the plasma-membrane ) ( is ( permitted ( to ( ( diffuse ( in ( only ( one direction ) ) ) ) ( by ( the ( growing ( actin filament ) ) ) ) ) ) ) ) ) ) ) ( -LRB- ( ( Figure 15 ) -RRB- ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (`` ``) (NNP Brownian) (NNP Ratchet) ('' '') (NN model)) (VP (VBZ states) (SBAR (IN that) (S (NP (DT a) (JJ protrusive) (NN force)) (VP (VBZ is) (VP (VBN exerted) (PP (IN during) (NP (NP (NN polymerization)) (PP (IN of) (NP (NN actin))))) (PP (IN by) (S (VP (VBG utilising) (NP (NP (DT the) (NN energy)) (PP (IN of) (NP (NP (JJ Brownian) (NN motion)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (DT the) (NN plasma-membrane)) (VP (VBZ is) (VP (VBN permitted) (S (VP (TO to) (VP (VB diffuse) (PP (IN in) (NP (RB only) (CD one) (NN direction))) (PP (IN by) (NP (DT the) (VBG growing) (NN actin) (NN filament)))))))))) (PRN (-LRB- -LRB-) (NP (NN Figure) (CD 15)) (-RRB- -RRB-))))))))))))) (. .)))
The &quot;Brownian Ratchet&quot; model states that a protrusive force is exerted during polymerization of actin by utilising the energy of Brownian motion in which the plasma-membrane is permitted to diffuse in only one direction by the growing actin filament (Figure 15).
(ROOT (S (NP (NNP Work)) (VP (VBZ is) (VP (VBN done) (SBAR (RB only) (IN if) (S (NP (DT a) (NN force)) (VP (VBZ is) (VP (VBN exerted) (PP (IN in) (NP (NP (DT the) (NN direction)) (PP (IN of) (NP (NN motion))))))))))) (. .)))