2.4 Summary and the Bigger Picture

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71

will produce oxygen gas. The gas will propel the polymersome forward. The movement

of the polymersome is directional due to the asymmetric structure of the particle. This

results in movement mimicking chemotaxis and can be used to carry drugs to diseased

sites in the body.

2.4 Summary and the Bigger Picture

Human movement on the molecular scale works by the stiff “head” of a molecular motor

moving along a fiber as if it were a street. The head movement is fueled by ATP, and

controlled by fast concentration changes of ions inside and outside of the muscle cell

that contains the walking head. The duration and the strength of muscle contraction

can also be controlled in this system. This system self-assembles to create muscles that

function on the macroscale.

Motor proteins and their corresponding fiber “streets” have been used extensively

in nanotechnology research. It is now possible to automate the assembly of such systems,

as well as to control the direction of several cargo “trucks” moving at the same time. It

is still difficult to load the motor protein or truck, however. In addition, the problems

of large-scale and long-duration movement have not yet been solved. Initial work has

demonstrated that some systems can be scaled up to micrometer size by self-assembly.

Biomimetic movement with molecules has not achieved purposeful carrying capac-

ities yet. But an initial self-assembled system allowed for movement in a tube. Another

system was able to use a sequence of enzymes to achieve chemotaxis that could be used

in drug delivery.

It is even more difficult to mimic motor-movement with other molecules. The only,

rather short, “street” that has been shown to give directional, planned movement is the

length of a rotaxane-type molecule. Only a few nanometers of movement is possible in

these systems. It is also difficult to load cargo onto the ring of a rotaxane.

Bibliography

[1]

Sharma A. In: Medical Biochemistry: Molecules to Disease. iBooks. 2016. https://itunes.apple.com/us/

book/medical-biochemistry-molecules/id1119168051?mt=11.

[2]

Krauss G. In: Biochemistry of Signal Transduction and Regulation. Weinheim, Germany: Wiley-VCH;

2014.

[3]

Raymaent I. Trends in Biochemical Sciences. 1994;19:129–134.

[4]

Kull FJ, Endow SA. Journal of Cell Science. 2013;126:9–19.

[5]

Vale RD, Milligan RA. Science. 2000;288:88–95.

[6]

Ikezaki K, Komori T, Sugawa M, Arai Y, Nishikawa S, Iwane AH, Yanagida T. Small. 2012;8:3035–3040.

[7]

Mukherjee S, Warshel A. PNAS. 2013;110:17326–17331.

[8]

Lampinen MJ, Noponen T. Journal of Theoretical Biology. 2005;236:397–421.

[9]

Goodman BS, Derr ND, Reck-Peterson SL. Trends in Cell Biology. 2012;22:644–652.

[10] Kikkawa M. The Journal of Cell Biology. 2013;202:15–23.