Biomedical Engineering Reference
In-Depth Information
an.RNA.anchor..RNA.is.then.hybridized.to.the.DNA-linker,.and.contains.a.short.segment.
that. includes. the. O
A
. for. TMV,. that,. when. mixed. with. assembly-competent. TMV. capsid.
proteins,.initiates.self-assembly.of.TMV.rods.(Mueller.et.al..2011)..This.technique.can.be.
used.in.conjunction.with.the.aforementioned.materials.synthesis.techniques.for.a.highly.
sophisticated,.spatially.controlled.templating.technique.
7.6.4 Photocatalysis and Alternative energy
Among. the. areas. of. modern. technology. that. could. beneit. from. the. use. of. viral.
nanoengineering,. photocatalysis. stands. out. as. a. prime. candidate.. There. are. numerous.
examples.in.nature.of.photocatalytic.systems.that.harvest.the.energy.of.sunlight.to.drive.
chemical. reactions. at. the. cellular. level.. Building. upon. the. nanoscale. arrangement. of.
chromophores.within.these.natural.systems,.it.is.possible.to.enhance.the.eficiency.of.solar.
cells,.and.increase.the.sensitivity.of.optical.sensors.
It.has.been.demonstrated.that.TMV.can.be.used.as.a.light-harvesting.system,.and.that.
chromophores.organized.along.the.highly.ordered.one-dimensional.capsid.structure.can.
exhibit.FRET..Through.the.use.of.genetically.modiied.TMV.capsid.proteins.that.exhibit.a.
cysteine.at.position.123.(S123C),.chromophores.can.be.attached.through.maleimide.or.other.
thiol-based. chemistries.. Through. this. approach,. two. different. chromophores,. Oregon.
Green,.and.Alexa.Fluor.594.could.be.conjugated.to.separate.batches.of.capsid.monomers..
When. the. individually. modiied. monomers. were. combined. under. proper. conditions,.
TMV. capsids. could. self-assemble,. which. had. both. the. chromophores. lining. the. interior.
cavity.. FRET. between. the. two. chromophores. could. be. demonstrated. by. illuminating. at.
the. excitation. maxima. of. the. irst. chromophore,. and. then. observing. emission. from. the.
second. chromophore. (Miller. et. al.. 2007).. More. recently,. further. genetic. modiication. of.
the.capsid.protein.reorganized.the.N-terminus.to.be.presented.on.the.interior.channel.of.
the.assembled.capsid..This.allowed.for.differential.attachment.of.two.chromophores.on.
a. preformed. capsid. through. orthogonal. linking. chemistry,. simplifying. the. process. for.
generating.a.photocatalytic.nanostructure.(Dedeo.et.al..2010).
Presently,.alternative.energy.technologies.are.receiving.a.large.economic.incentive,.yet.
there.remain.inherent.challenges.associated.with.them..Poor.eficiency.is.a.constant.issue.
for.battery.technologies,.and.prevents.widespread.adoption..It.is.recognized.that.increased.
surface.area.at.the.nanoscale.can.greatly.enhance.the.eficiency.of.the.said.technologies;.
and.reliable,.controllable,.and.cost-effective.methods.to.realize.this.are.being.explored.
One.approach.is.to.leverage.nanobiological.structures,.such.as.virus.capsids,.as.templates.
to.generate.increased.surface.area..TMV.that.has.been.genetically.modiied.with.cysteine.
residues. at. position. 3. (TMV1cys). has. been. shown. to. self-assemble. on. gold. surfaces. in.
a. vertical. manner,. creating. a. carpet-like. structure.. The. vertical. alignment. of. the. viruses.
is. a. result. of. the. 3′. cysteine. being. the. only. residue. that. can. chemically. bind. to. the. gold.
surface.. Other. cysteine. residues. introduced. along. the. capsid. superstructure. are. slightly.
recessed,. which. prevent. interaction. with. the. gold. substrate.. These. remaining. cysteines.
act.as.nucleation.points.for.the.reduction.of.palladium,.which.is.followed.by.electroless.
deposition. of. nickel. or. cobalt. for. incorporation. into. batteries.. These. virus-templated.
structures. have. a. signiicant. increase. in. surface. area,. and. consistently. outperformed.
nontemplated. structures. when. integrated. into. a. NiO-Zn. battery. system. (Royston. et. al..
2007).As.can.be.seen.in.Figure.7.13,.addition.of.an.∼50.nm.silicon.layer.on.top.of.the.nickel.
using.physical.vapor.deposition.(PVD).resulted.in.a.composite.silicon.anode.with.increased.
capacity.and.stability.over.commercially.available.graphite.anodes.(Chen.et.al..2010).
