Nanostructures such as functionalized nanoparticles and superlattices have wide-ranging applications in diverse areas. [1][2][3][4] Although these materials are invariably used in the form of aqueous/organic dispersions, ultrathin films, or bulk powders, Giannellis and co-workers have recently pioneered an approach to preparing functionalized inorganic nanostructures with liquidlike behavior. [5,6] These are produced by electrostatically grafting an organic canopy layer onto the surface of charged nanoparticles of silica, [7] iron oxides, [7] and titania [8] for example, to provide a fluidization medium for the preparation of solvent-free nanoparticle ionic fluids. Like nanoscale objects in general, proteins exhibit persistent structures with dimensions that exceed the range of their intermolecular forces, such that liquid-vapor co-existence is unattainable. [9] As a consequence, solid-state proteins sublime at low pressures or thermally degrade under ambient conditions: thus, there are no known liquid proteins in the absence of solvent.Herein, we report, to our knowledge, the first example of a solvent-free liquid protein. Specifically, we report the preparation and properties of a protein melt based on a stoichiometric ferritin-polymer nanoscale construct with surface modifications that extend the range of intermolecular interactions to a length scale that is commensurate with fluidity in the absence of water. Moreover, we show that these spherically shaped nano-constructs undergo anisotropic ordering during melting at 30 8C to produce a viscoelastic protein liquid that exhibits thermotropic liquid-crystalline behavior, and which subsequently transforms to a Newtonian fluid at temperatures above 40 8C and is stable up to a temperature of 405 8C. The method, which utilizes the sitespecificity of surface amino acid residues and high degree of uniformity in ferritin molecular architecture to produce discrete single-component ferritin-polymer constructs (Supporting Information, Figure S1), should be readily accessible to exploitation as a facile route to solvent-free liquid proteins and enzymes in general.Electrostatically induced complexation of cationized ferritin (C-Fn), comprising approximately 240 covalently coupled N,N-dimethyl-1,3-propanediamine (DMPA) groups per molecule (10 DMPA per subunit; Supporting Information, Figure S2), with the anionic polymer surfactant C 9 H 19 -C 6 H 4 -(OCH 2 CH 2 ) 20 O(CH 2 ) 3 SO 3 À (S) resulted in the formation of the ionic nanoconstruct [C-Fn][S]. Sedimentationcoefficient distributions obtained by analytical ultracentrifugation of extensively dialyzed aqueous solutions of [C-Fn][S] showed a single peak centered at 37 S compared with values of 51 or 0.5 S for C-Fn or S alone (Supporting Information, Figure S3). The decrease in density of the conjugate compared with non-complexed C-Fn, as well as the absence of unbound surfactant, were consistent with a discrete proteinpolymer ionic construct. Significantly, calculations based on comparative density variations coupled with ...

The morphology of micelles formed by two novel metallosurfactants has been studied by small-angle neutron scattering (SANS) and small-angle-X-ray scattering (SAXS). The two surfactants both contain a dodecyl chain as the hydrophobic moiety, but differ in the structure of the head group. The surfactants are Cu(II) complexes of monopendant alcohol derivatives of a) the face-capping macrocycle 1,4,7-triazacyclanonane (tacn), and b) an analogue based upon the tetraazamacrocycle 1,4,7,10-tetraazacyclododecane. Here, neutron scattering has been used to study the overall size and shape of the surfactant micelles, in conjunction with X-ray scattering to locate the metal ions. For the 1,4,7,10-tetraazacyclododecane-based surfactant, oblate micelles are observed, which are smaller to the prolate micelles formed by the 1,4,7-triazacyclononane analogue. The X-ray scattering analysis shows that the metal ions are distributed throughout the polar head-group region, rather than at a well-defined radius; this is in good agreement with the SANS-derived dimensions of the micelle. Indeed, the same model for micelle morphology can be used to fit both the SANS and SAXS data.

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Nanostructures such as functionalized nanoparticles and superlattices have wide-ranging applications in diverse areas. [1][2][3][4] Although these materials are invariably used in the form of aqueous/organic dispersions, ultrathin films, or bulk powders, Giannellis and co-workers have recently pioneered an approach to preparing functionalized inorganic nanostructures with liquidlike behavior. [5,6] These are produced by electrostatically grafting an organic canopy layer onto the surface of charged nanoparticles of silica, [7] iron oxides, [7] and titania [8] for example, to provide a fluidization medium for the preparation of solvent-free nanoparticle ionic fluids. Like nanoscale objects in general, proteins exhibit persistent structures with dimensions that exceed the range of their intermolecular forces, such that liquid-vapor co-existence is unattainable.[9] As a consequence, solid-state proteins sublime at low pressures or thermally degrade under ambient conditions: thus, there are no known liquid proteins in the absence of solvent.Herein, we report, to our knowledge, the first example of a solvent-free liquid protein. Specifically, we report the preparation and properties of a protein melt based on a stoichiometric ferritin-polymer nanoscale construct with surface modifications that extend the range of intermolecular interactions to a length scale that is commensurate with fluidity in the absence of water. Moreover, we show that these spherically shaped nano-constructs undergo anisotropic ordering during melting at 30 8C to produce a viscoelastic protein liquid that exhibits thermotropic liquid-crystalline behavior, and which subsequently transforms to a Newtonian fluid at temperatures above 40 8C and is stable up to a temperature of 405 8C. The method, which utilizes the sitespecificity of surface amino acid residues and high degree of uniformity in ferritin molecular architecture to produce discrete single-component ferritin-polymer constructs (Supporting Information, Figure S1), should be readily accessible to exploitation as a facile route to solvent-free liquid proteins and enzymes in general.Electrostatically induced complexation of cationized ferritin (C-Fn), comprising approximately 240 covalently coupled N,N-dimethyl-1,3-propanediamine (DMPA) groups per molecule (10 DMPA per subunit; Supporting Information, Figure S2 Protein melts were prepared in the absence of water by lyophilization of the aqueous [C-Fn][S] solutions to produce a low-density solid that was subsequently annealed at 50 8C to produce a transparent, viscous, red liquid that remained fluid when cooled to room temperature, but re-solidified at À50 8C (Figure 1). TEM studies of the melt revealed discrete electron-dense nanoparticles, approximately 8 nm in diameter, indicating that the protein nanostructure remained structurally intact in the liquid state (Supporting Information, Figure S4). The melts were readily soluble in water or dichloromethane. Thermogravimetric analysis of the melt gave a water content of less than 2 % and a resid...

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