TiO2 in CCMV with Photocatalytic Activity

1
Exploiting Protein Cage Dynamics for Engineering
Active Nanostructures NSF NIRT
CBET-0709358Brian Bothnerad, Yves Idzerdabd,
Mark Youngcd, Trevor Douglasad (PI) a.Department
of Chemistry and Biochemistry, b. Department of
Physics, c. Department of Plant Sciences, d.
Center for Bio-Inspired Nanomaterials, Montana
State University, Bozeman, MT 59717

Objectives The development of protein cage
architectures as dynamic size and shape
constrained templates for nanomaterials synthesis
using three integrated components - Active
Interfaces, Cage Dynamics, and Confinement.
Internally Constrained Proteins for Catalyst
Scaffolds
TiO2 in CCMV with
Photocatalytic Activity
Polymer in Hsp increased thermal stability
Nanoparticles of TiO2 were grown inside the CCMV
capsid by polymerization of a Ti-oxo anion
(Ti-BALDHI) at high pH.  Pair Distribution
Function (PDF) analysis showed a structure
similar to beta-TiO2, with a crystalline domain
size of 1.3nm.  This is significantly smaller
than the particle sizes shown by TEM, and
indicates that each protein cage likely contains
numerous small crystallites, rather than a single
TiO2 crystal.  The virus-templated TiO2
nanoparticles have been shown to by
photochemically active, and may be useful for
light-harvesting applications.
A cross-linked branched polymer can be initiated
and synthesized within the interior cavity of a
protein cage architecture. This polymer network
allows for the spatial control of pendant
reactive sites and dramatically increases the
stability of the cage architecture extending the
thermal stability of the protein cage to at
least 120 C. The polymer was generated
sequentially coupling multifunctional monomers
using click chemistry to create a branched
cross-linked polymer network through generation
2.5 where it was limited by the size of the
cavity.
A range of protein cage architectures can be used
as synthetic templates
The interior, exterior, and subunit interfaces
can be chemically and genetically modified.
Protein cage library size range from 30 to 10 nm
diameter. CCMV (30nm), Ferritin (12 nm), sHsp
(12 nm), Dps (10 nm)
Generations 2.5 exhibited exceptional stability
upon exposure to heat. The G41C native cage
decomposes upon exposure to 120 C for 10 min
while generation 2.5 remains intact upon exposure
to 120 C for 30 min.
TEM of unstained (right) and uranyl acetate
stained (left) CCMV reacted with Ti-BALDHI. The
diffraction pattern (insert) could be indexed to
b-TiO2. The scale bars are 100 nm.
Coordination
polymer in Hsp
a-Fe2O3 in Pf_Fn with
Photocatalytic Activity
A branched iron-phenanthroline based coordination
polymer has been constructed in a water based
system using a click chemistry approach to link
monomeric coordination complexes together within
a protein cage nano-architecture, which acts both
a template and a sized constrained reaction
environment.
Using ferritin from the hyperthermophile
Pyrococcus furiosis we have mineralized a
disorodered Fe(O)OH within the protein cage and
transformed it to hematite at 100ºC in the
presence of oxalate. The protein remains intact
during this process. The hematite mineral acts
as a semiconductor with a bandgap in the visible.
Coomassie stained acid urea denaturing gel
evidence of cross-linking of the protein
subunits. As the generations increase across the
gel, the monomer, which is dominant in G0.0 and
G0.5, gradually decreases with a parallel
increase in intensity at the top of the gel.
The ratio of the absorbance at 530 to 280 nm at
each generation is related to the number of
Fe(II) moieties per a cage. The absorbance at 530
nm is only due to the Fe(az-phen)32, while the
absorbance at 280 nm is from both the protein and
the Fe(az-phen)32.
Cartoon schematic for the conversion of a
disordered iron oxide to an ordered photoactive
iron oxide.
Photocurrents generated by the ß-TiO2 / CCMV
composites upon exposure to a high intensity LED
(420 nm) or UV (365 nm) light source. The
response to the visible illumination is
negligible.
Experimental PDF compared with ß-TiO2 and NaCl
phases. A good fit was obtained through a linear
combination of the two components.
The stepwise formation of a coordination polymer
inside Hsp G41C starts at the internal cysteine
of each protein subunit. Each generation is added
through the introduction of either an alkyne or
azide compound.
Rapid and Reversible Environmental Response
The development of rotein cages that can react to
environmental signals leading to changes in
confomation, stability, and chemical potential
are being investigated
Redox active switching of DPS cages.
C101S
WT
flexible
rigid
DPS
swollen
Noncovalent dye binding shows that reduction of
the disulfide in WT DPS decreases cage thermal
stability. A mutant form lacking the disulfide
is insensitive to redox potential. O oxidized,
R reduced.
frequency
closed
Transmission electron micrographs of (A)
unstained and (B) stained refluxed Pf-Fn. The
dark electron dense cores in (A) have an electron
diffraction pattern (insert) consistent with
?-Fe2O3.
Photocurrent generated upon exposure of hematite
in Pf_Fn with methyl viologen (blue dash-dotted),
ferrihydrite in Pf_Fn (red dashed), and methyl
viologen (black solid) to a high intensity LED
light.
time
Quartz crystal microbalance analysis of the
closed to swollen transition. Modulus of CCMV
protein cages reversibly transitions between two
states, controlled with pH and divalent cations.
40 50 60 70 80
90 C