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Host–guest encapsulation of materials by assembled virus protein cages


Self-assembled cage structures of nanometre dimensions can be used as constrained environments for the preparation of nanostructured materials1,2 and the encapsulation of guest molecules3, with potential applications in drug delivery4 and catalysis5. In synthetic systems the number of subunits contributing to cage structures is typically rather small3,6. But the protein coats of viruses (virions) commonly comprise hundreds of subunits that self-assemble into a cage for transporting viral nucleic acids. Many virions, moreover, can undergo reversible structural changes that open or close gated pores to allow switchable access to their interior7. Here we show that such a virion — that of the cowpea chlorotic mottle virus — can be used as a host for the synthesis of materials. We report the mineralization of two polyoxometalate species (paratungstate and decavanadate) and the encapsulation of an anionic polymer inside this virion, controlled by pH-dependent gating of the virion's pores. The diversity in size and shape of such virus particles make this a versatile strategy for materials synthesis and molecular entrapment.

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Figure 1: Cryo electron microscopy and image reconstruction of the cowpea chlorotic mottle virus (CCMV).
Figure 2: Schematic illustration of the synthetic approach for mineralization within the virus particle.
Figure 3: TEM images of paratungstate-mineralized virus particles after isolation by centrifugation on a sucrose gradient.
Figure 4: High-resolution TEM image of a corner of an individual paratungstate core, encapsulated within the virion.
Figure 5: Encapsulation of polyanetholesulphonic acid (PAS) within the CCMV virion.


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We thank S. Brumfield, D. Mogk and G. Myer for experimental assistance, and R.Lakis for assistance with the electron microscopy.

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Correspondence to Trevor Douglas or Mark Young.

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Douglas, T., Young, M. Host–guest encapsulation of materials by assembled virus protein cages. Nature 393, 152–155 (1998).

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