Translocation through Channels

This result observed in the nanofluidic channel device, where longer molecules move faster, is counterintuitive and is the opposite of the results observed in nanopores where the longer chains take longer times to translocate. 

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Structural basis for sugar translocation through malto-porin channels at 3.1 A resolution. Science 267 512-514, 1995. 

Schirmer, T., T. A. Keller, Y.-F. Wang, and J. P. Rosenbusch. 1995. Structural basis for sugar translocation through maltoporin channels at 3.1 A resolution. Science 267 512-514. 

The compound dicyclohexylcarbodiimide (DCCD) inhibits proton translocation through F0 by reacting with the carboxyl group of a single glutamate residue in the channel-forming loop of the proteolipid. 

One of the characteristic motifs of heavy metal P-type ATPases is the CPX (commonly CPC) motif within transmembrane domain 6, widely regarded as a part of the cation channel (Silver and Phung, 1996) (Fig. 1). The possible role for these cysteines in the transmembrane domain may be the coordination of a heavy metal during its translocation through the cation channel. While these cysteines have proved to be essential for the function of some HMPAs, their exact role in catalysis is yet to be fully understood (Bissig et al., 2001 Forbes and Cox, 2000). 

The H+ translocates through the membrane in three steps. First it adsorbs into a half channel of the membrane, then it connects with a proton acceptor site on the rotating Fi ring. In a rotation, the proton is back-donated to the empty other half-channel of the membrane, that transfers the proton to the other side of the membrane. Rotational motion will only occur when one half-channel is unoccupied by a proton and the other half is empty. 

Y. Q. Xue and M. D. Chen, Dynamics of molecules translocating through carbon nanotubes as nanofluidic channels. Nanotechnology, 17, 5216 (2006]. 

The particles start at site i = 1 and hop inside the channel between the adjacent sites with the rates until they either translocate through the channel, exiting from site N with the rate r, or exit the the wrong side -site 1, with the rate [76-80], The probability P,(t) for the particle to be at site i at time t then obeys the (forward) ME... 

Muthukumar, M. and Kong, C.Y., 2006. Simulation of polyma- translocation through protein channels, Proc. Natl. Acad. Sci. USA, 103, 5273-5278. 

Wong, C.T.A. and Muthukumar, M., 2008a. PolymCT translocation through a cylindrical channel, J. Chem. Phys., 128,154903. 

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