Biomedical Engineering Reference
In-Depth Information
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Legend:
Caesin
Kinesin
ssDNA
Cargo
Microtubule
Figure 4.4
(See companion CD for color igure.) . Assembly-line. geometries. for. directed. sorting. and. patterning.. (a).
Microtubules.(cylinders).can.be.ixed.to.a.platform.in.speciied.design.patterns,.then.motor-cargos.added.that.
bind.and.track.along.the.microtubule.length..Complexity.in.this.approach.can.be.achieved.by.the.combination.
of.multiple.simple.designs..Gaps.in.microtubule.patterns.would.potentially.“dead.end”.kinesins..(b).A.concep-
tual.asterisk.pattern.for.collection.and.concentration.of.essential.building.blocks.at.a.central.assembly.point..
(c).Parallel.processing.routes.deliver.unique.building.blocks.for.optimized.spatial.assembly..(d).An.alternative.
geometry.with.Kinesins.ixed.to.a.platform.while.microtubules.with.attached.cargo.are.shuttled..Microtubules.
are.functionalized.with.a.short.ssDNA.that.is.partially.complementary.to.a.longer.strand.bound.to.the.cargo..
The.deposition.of.cargo.at.a.desired.location.is.favored.through.preferential.hybridization.with.a.full-length.
complementary.strand..(E).Strategy.in.which.sequential.microtubule.synthesis.is.accomplished.using.different.
functionally.modiied.tubulins.to.facilitate.track-speciic.binding.sites.for.cargo,.in.this.case.for.the.assembly.of.
a.nanoscale.ice-cream.cone.
Microtubules. are. dynamic. polymers.. Genetic. alterations,. protein. association,. tubulin.
modiications,.chemical.manipulation.as.well.as.temperature,.presence.of.GTP,.and.other.
factors.all.affect.their.dynamics..Microtubule.length.and.rigidity.will.affect.what.is.termed.
“the.persistence.length,”.or.the.distance.a.ilament.can.travel.before.it.alters.direction.from.
its. original. path.. For. Taxol-stabilized. microtubules. persistence. length. is. 5.2.mm. versus.
actin,. which. is. only. 17.7.μm. as. determined. by. analysis. of. thermally. driven. luctuations.
(Gittes.et.al.,.1993)..Rigidity.of.the.microtubule.ilament.is.important.when.constructing.
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