Biology Reference
In-Depth Information
virions can be disassembled and re-assembled
. This is typically
achieved by first exposing the particles to a disassembly buffer, whereby
coat proteins can then be-reassembled by dialysis against an assembly
buffer. These techniques are extensively discussed in Chapter 5 and the
reader is referred to references therein.
Assembly and disassembly of viruses is well understood for some
viruses, and
in vitro
assembly methods play an important role in
nanotechnology. These disassembly techniques allow release of the
natural cargo (nucleic acid) and are used to: (i) generate empty particles
(Section 3.6) and (ii) hybrid VNPs. Hybrid VNPs or hybrid materials in general
are a combination of two or more different components. For example, a VNP
with an encapsulated gold core is considered a hybrid VNP consisting of
the proteins shell and gold core. Re-assembly allows packaging of artificial
cargos and leads to the generation of hybrid VNPs. The artificial cargo can
include drug molecules, imaging moieties, synthetic polymers, or inorganic
nanoparticles (discussed in detail in Chapter 5).
Re-assembly techniques also allow generation of particles with altered
symmetry, for example, icosahedral particles with
in vitro
T =
1,
pseudo
T =
2, and
T =
, 2007). Not only
can differently sized particles be generated, the coat proteins can also be
assembled into structures, such as tubes and sheets. It is truly fascinating
that a single protein, which
3 symmetries can be generated using BMV (Sun
et al.
self-assembles into discrete, uniform,
and monodisperse particles, can also be assembled into a range of
different structures. This level of control and flexibility cannot be achieved
with synthetic nanobuilding blocks. VNPs are intriguing materials, and
understanding the self-assembly processes is expected to have significant
impact on a range of technologies, including “smart” protein and/or
inorganic nanoparticle design.
The self-assembly of viral rods, especially TMV, has also been extensively
studied and has led to a range of applications in nanotechnology, the
examples of which are discussed below.
in planta
..1 BMV and CCMV
The coat proteins of the plant viruses BMV and CCMV are extremely flexible.
BMV and CCMV coat proteins can assemble into
T = 3
particles, as well as into sheets, stacks, and tubular structures (Bancroft
pseudo T
= 2, and
et
al.
, 1967; Krol
et al.
, 1999; Pfeiffer
et al.
, 1976; Pfeiffer & Hirth, 1974). BMV
particles have also been observed in a
T =
1 geometry;
T =
1 particles are
formed
after cleavage of the N-terminal 63 or 35 amino acid residues
of the coat protein by an endogenous protease or by trypsin.
in vitro
T
= 3 particles
could also be directly condensed into
T
= 1 particles without undergoing
complete disassembly (Fig. 3.6) (Larson
et al.
, 2005; Lucas
et al.
, 2001).
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