Biology Reference
In-Depth Information
to the nucleation and crystallization event (Douglas & Young, 1998). This is
similar to the mechanism the iron storage protein ferritin uses to sequester
iron: the high charge density on the interior surface of the 12 nm-sized
protein cage leads to nucleation of soluble Fe(II), which is subsequently
oxidized using O
resulting in encapsulated iron oxide (Fe
O
) nanoparticles
2
2
3
(for a review see Uchida
., 2007).
These principles can be extended to generate a range of materials within
the CCMV cage; the requirement is that the precursors are negatively charged.
Materials such as titanium oxide (TiO
et al
) (Klem
et al
., 2008) and Prussian blue
2
nanoparticles (de la Escosura
., 2008) have been synthesized within
CCMV. Prussian blue nanoparticles are magnetic materials with potential
applications in data storage devices, and the synthesis of monodisperse
particles remains challenging. Monodisperse 18
et al
±
1.7 nm-sized Prussian
blue nanoparticles were synthesized within the internal cavity of CCMV.
Herein, precursor anions were added to CCMV, and nucleation was initiated
by photoreduction (de la Escosura
., 2008).
The beauty of using VNPs as templates is that one can alter the surface
properties and charge of the template using mutagenesis. It was demon-
strated that by altering the charge of the interior surface of the CCMV
particle from cationic to anionic, the resulting intact particles favored the
encapsulation of cationic species (Douglas
et al
., 2002). A mutant was
constructed in which all the basic residues on the N-terminus of the coat
proteins were substituted with the negatively charged amino acid Glu
(Brumfield
et al
., 2004). It was found that, because of the electrostatic
alterations, the mutant favors strong interaction with ferrous and ferric
ions, and that oxidative hydrolysis led to the size-constrained formation of
iron oxide (Fe
et al
O
) nanoparticles encapsulated in the viral cage (Douglas
et
2
3
al
., 2002).
To date, only two VNP platforms have been utilized as containers for
nucleation of inorganic materials inside the internal cavity: CCMV and the
phage T7 (note: a range of other VNPs have been utilized to encapsulate
materials as described in Chapter 5). Empty T7 ghost particles were utilized
as nanocontainers and filled with a fluorescent europium complex (Liu
et
al
., 2006). The synthesis mechanism is
the same as described for CCMV, that is, electrostatically driven nucleation
of soluble precursors.
., 2005) and metallic cobalt (Liu
et al
6.1.1 Potenial Applicaions of VNPs with Mineralized Cores Lie 
within the Fields of Data Storage and Medicine
Iron oxide nanoparticles, for example, have been shown to be promising
candidates for biomedical imaging such as magnetic resonance imaging
Search WWH ::




Custom Search