Protein cage nanoparticles as secondary building units for the synthesis of 3-dimensional coordination polymersElectronic supplementary information (ESI) available: Dynamic light scattering, mass spectrometry, SAXS analysis and modeling. See DOI: 10.1039/c0sm00039f

Coordination polymers (CPs) have garnered much attention in the past several years for the relative facility of their synthesis and potential benefit in diverse applications such as gas separation, energy storage, drug delivery and as novel bio-imaging compounds. To date there have been relatively few reports of CP assembly from peptide-based precursors. CPs generated from biomolecules offer several potential advantages over their synthetic counterparts including extensive structural diversity, intrinsic chirality and the capacity for introduction of catalytic or similar biological functionalities. Here we describe the construction of CPs utilizing protein cage nanoparticles (PCN) as secondary building units. The dodecameric Dps protein cage from the hyperthermophilic archeon Sulfolobus solfataricus was modified for metal binding by chemical ligation of metal-chelating functionalities to the cage exterior. Treatment of modified PCN with transition metals results in the rapid formation of PCN-metal assemblies. These assemblies are characterized by a combination of dynamic light scattering, electron microscopy, small angle X-ray scattering and gas sorption studies. Exterior modification of Dps protein cages with metal-chelating groups and exposure to transition metals results in formation of 3-D coordination polymer networks, characterized by electron microscopy and small angle X-ray scattering.