Biomedical Engineering Reference
In-Depth Information
100
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48°C
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430 nm
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Time (min)
Figure 1.10
(See companion CD for color igure.)
.Thermal.annealing.of.origami.with.22-mer.sticky.ends,.designed.to.form.
1D.polymer.chains..DNA.origami.do.not.assemble.into.chains.until.the.temperature.drops.below.50°C..Template.
strand,.20.eq.of.interior.staple.strands,.and.1.eq.of.sticky.end.strands.were.heated.to.90°C.in.1X.TAE.buffer,.then.
cooled.slowly.
present;.at.lower.temperatures,.the.designed.sticky-end.interactions.allow.formation.of.1D.
polymers.with.well-controlled.registration.and.orientation.
A. clever. assembly. approach. was. demonstrated. by. Endo. et. al.. (2010).. Taking. advan-
tage.of.the.strong.pi-stacking.interactions,.which.tend.to.make.exposed.helix.ends.stick.
together,. this. group. added. an. element. of. shape. complementarity. by. making. origami.
pieces.with.convex.and.concave.edges..The.“pegs”.and.“holes”.were.designed.so.that.up.
to.ive.origami.could.be.mixed.together.and.would.only.be.able.to.assemble.in.one.order..
In. addition,. speciic. base-pairing. interactions. were. provided. via. “sticky. ends”. located.
where. pegs. met. holes.. Since. all. the. “jigsaw. pieces”. use. the. same. template. strand,. each.
had.to.be.annealed.separately.and.puriied.by.gel.iltration.before.mixing..Assembly.of.
the.ive-piece.jigsaw.puzzle.required.10-50.h.of.slow.annealing.for.optimal.yield.of.24%.
based.on.monomer.conversion..Zhao.et.al..(2010).made.small.DNA.tiles.with.protruding.
sticky. ends. that. acted. as. staple. strands. to. fold. M13. template. DNA. into. hybrid. origami.
structures.. This. approach. did. produce. structures. up. to. four. times. larger. than. a. “plain.
vanilla”.origami,.as.can.be.seen.in.Figure.1.11,.but.the.larger.structures.often.had.vacan-
cies.where.one.of.the.“staple.tiles”.was.absent.
Rothemund's. original. rectangular. origami. design. gives. a. structure. that. is. curved. in.
solution,. rather. than. lat,. as. shown. in. Figure. 1.12.. The. evidence. for. this. solution. struc-
ture.is.based.on.both.structural.predictions.(Kim.et.al..2011a).and.the.propensity.of.the.
rectangular.origami.to.form.helical.ribbons.rather.than.lat.strips.when.the.short.ends.of.
the.rectangles.are.joined.together.by.pi-stacking.interactions.(Woo.and.Rothemund.2011)..
These.helical.ribbons.can.sometimes.be.observed.directly,.but.more.often.they.fragment.
when.they.land.on.the.mica.substrate,.producing.a.characteristic.pattern.of.short.segments.
and.offsets..Several.approaches.have.been.taken.to.reengineer.this.basic.origami.design.
