Biomedical Engineering Reference
In-Depth Information
demonstrated. one-dimensional. arrays. of. MS2. with. nanometer. precision.. By. designing.
new. DNA. origami. tiles. and. probes,. this. approach. for. nanoengineered. templating. could.
easily.be.modiied.to.produce.micrometer-sized.self-assembled.structures.from.nanoscale.
components.
7.5 Cowpea Mosaic Virus
7.5.1 general Properties, Structure, and Assembly
First.identiied.as.a.pathogen.in.cowpeas.in.West.Africa.over.50.years.ago,.cowpea.mosaic.
virus. (CPMV). has. become. synonymous. with. virus-based. nanoengineering.. It. has. been.
the. subject. of. intense. scientiic. research. because. the. virions. are. remarkably. stable. and.
are.easy.to.propagate.and.obtain.in.high.yields..Early.work.with.bioengineering.CPMV.
dealt.with.the.display.of.foreign.peptides.on.the.capsid.surface.for.the.purpose.of.epitope.
presentation. and. vaccine. development.. Although. this. work. was. groundbreaking. in. the.
ield.of.biotechnology,.it.is.beyond.the.scope.of.this.text,.and.we.refer.the.reader.to.a.review.
by.Sainsbury.for.a.more.in-depth.treatment.of.the.topic.(Sainsbury.et.al..2010).
CPMV.is.an.icosahedral,.nonenveloped.virus.in.the.family.
Comoviridae
..It.infects.legumes.
utilizing. leaf-eating. beetles. or. grasshoppers. as. transmission. vectors,. and. is. a. Biosafety.
Level. 1. pathogen. (Evans. 2009).. The. assembled. capsid. is. 28.nm. in. diameter. and. exhibits.
pseudo. T.=.3.icosahedral.symmetry,.as.it.is.formed.from. 60.copies.each.of.two.different.
capsid. proteins. (Lin. et. al.. 1999).. The. two. distinct. capsid. proteins. are. characterized. as.
large.(L),.and.small.(S).subunits,.with.the.S.subunit.(24.kDa).containing.one.domain.(A),.
and. the. L. subunit. (42.kDa). being. made. up. of. two. domains. (B. and. C). (Figure. 7.9).. The.
asymmetric.unit.of.quasi-equivalence.is.made.up.of.one.copy.of.each.domain,.hence.the.
pseudo.T.=.3.designation.(the.L.subunit.is.equivalent.to.two.capsid.monomers.in.a.normal.
T.=.3.symmetry)..The.assembled.capsid.displays.projections.at.the.threefold.and.ivefold.
rotation.axes.and.valleys.at.the.twofold.axes.(Evans.2008)..The.capsids.are.known.to.be.
A domain
(S subunit)
C domain
(L subunit)
B domain
(L subunit)
(a)
(b)
Figure 7.9
(See companion CD for color igure.)
. The. CPMV. structure.. The. capsid.(a). exhibits. pseudo. T.=.3. icosahedral.
symmetry..The.asymmetric.unit.(b).is.comprised.of.two.proteins:.the.small.subunit.(S).contains.the.A.domain.
(green);.the.large.subunit.(L).contains.the.B.domain.(red).and.C.domain.(yellow).
