Biology Reference
In-Depth Information
HK97 wild-type and mutant particles can be produced and assembled in
E
from the expression of just two viral gene products: gp4 (a protease,
which is facilitating maturation) and gp5 (the coat protein). Maturation of the
capsids can be triggered
.
coli
in vitro
by chemical or low-pH treatments (Conway
et al
., 2001; Gan
et al
., 2006; Lata
et al
., 2000; Lee
et al
., 2008; Wikoff
et al
.,
2000).
It was not until very recently that HK97 became a platform for utilization
in nanotechnology. The team led by Johnson (The Scripps Research
Institute, La Jolla, CA) is currently exploring the feasibility of the particles
for biomedical applications. Its biochemistry and the large interior volume
of the matured head make it a potentially interesting candidate for drug-
delivery strategies.
.. P: A Bacteriophage
The
bacteriophage P22 is closely related to HK97
(see Section 2.2.7). Like HK97, the phages consist of a head and a tail, are not
enveloped, and encapsidate a linear double-stranded DNA genome. The head
has icosahedral
Salmonella typhimurium
T
= 7 symmetry and a diameter of about 58 nm (Chang
et
al
., 2006). Also for P22, it is the capsid that is of interest for nanotechnology.
Wild-type P22 as well as VLPs can be expressed with high yields, and
in
vitro
assembly methods have been established (Botstein
et al
., 1972; Fuller
& King, 1982; King
., 1976; King & Casjens, 1974). A recent pilot study
demonstrated that chemical functionalities can be installed on the outer
surface of the capsid (Kang
et al
., 2008), which opens the door for future
development of the candidate VNP.
et al
..10 t: A Bacteriophage
T7 also shares similarities with HK97 and P22. T7 is a double-stranded DNA
(linear genome) head-tail coliphage. The head is symmetric with icosahedral
T
., 2007).
Empty T7 particles can be produced with ease using various methods:
empty capsids are assembled prior to DNA packing and can be isolated (in low
yields) at the early stage of the infection (Studier, 1972). T7 ghost particles
can also be prepared by osmotic shock with yields of about 55% (Liu
= 7 symmetry and about 60 nm in diameter (Agirrezabala
et al
et al
.,
2005), or by alkaline lysis with yields as high as greater than 98% (Liu
.,
2006). The availability of empty particles has led to the exploration of T7
for nanotechnology. Empty T7 phages have been utilized as nanocontainers
for the encapsulation or constrained synthesis of materials (Liu
et al
et al
., 2005,
2006) (discussed in Chapter 5).
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