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 ...

Many known complex oxides of general formula A(2)B(2)X(7) adopt the pyrochlore structure, a key structure-type that has been shown to demonstrate a vast range of useful physical properties. Areas currently of much interest with respect to pyrochlores, include metal-insulator transitions, magnetic frustration/spin ices, magnetoresistance, superconductivity, ferroelectrics, O/F ionic conductivity, mixed conductivity, pigments and catalysis. We present some recent results on three types of pyrochlore materials that show unusual magnetic, optical and electronic behaviours associated with subtle structural and compositional changes. High-resolution powder neutron diffraction studies of the superconducting Cd(2)Re(2)O(7) and the ferroelectric Cd(2)Nb(2)O(7) have been undertaken on material cooled below room temperature. Both Cd(2)Re(2)O(7) and Cd(2)Nb(2)O(7) exhibit small structure distortions, in each case involving a distortion from a cubic unit cell, on cooling below approximately 180 K and possible models that can be used to describe the low-temperature structures and associated atomic displacements are developed and described in this article. A range of materials of the general formula Ca(1-x)Ln(x)TaO(2-x)N(1+x), x= 0.5 and x= 1, Ln = La-Yb have been synthesised and shown to adopt pyrochlore and/or perovskite structures. The absorption spectra of these materials are discussed in terms of their structures and compositions.

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The cyanobacterial culture HT-58-2 was originally described as a strain of with the ability to produce tolyporphins, which comprise a family of distinct tetrapyrrole macrocycles with reported efflux pump inhibition properties. Upon reviving the culture from what was thought to be a nonextant collection, studies of culture conditions, strain characterization, phylogeny, and genomics have been undertaken. Here, HT-58-2 was shown by 16S rRNA analysis to closely align with strains and not with isolates. Light, fluorescence, and scanning electron microscopy revealed cyanobacterium filaments that are decorated with attached bacteria and associated with free bacteria. Metagenomic surveys of HT-58-2 cultures revealed a diversity of bacteria dominated by, 97% of which are species. A dimethyl sulfoxide washing procedure was found to yield enriched cyanobacterial DNA (presumably by removing community bacteria) and sequence data sufficient for genome assembly. The finished, closed HT-58-2Cyano genome consists of 7.85 Mbp (42.6% G+C) and contains 6,581 genes. All genes for biosynthesis of tetrapyrroles (e.g., heme, chlorophyll, and phycocyanobilin) and almost all for cobalamin were identified dispersed throughout the chromosome. Among the 6,177 protein-encoding genes, coding sequences (CDSs) for all but two of the eight enzymes for conversion of glutamic acid to protoporphyrinogen IX also were found within one major gene cluster. The cluster also includes 10 putative genes (and one hypothetical gene) encoding proteins with domains for a glycosyltransferase, two cytochrome P450 enzymes, and a flavin adenine dinucleotide (FAD)-binding protein. The composition of the gene cluster suggests a possible role in tolyporphin biosynthesis. A worldwide search more than 25 years ago for cyanobacterial natural products with anticancer activity identified a culture (HT-58-2) from Micronesia that produces tolyporphins. Tolyporphins are tetrapyrroles, like chlorophylls, but have several profound structural differences that reside outside the bounds of known biosynthetic pathways. To begin probing the biosynthetic origin and biological function of tolyporphins, our research has focused on studying the cyanobacterial strain, about which almost nothing has been previously reported. We find that the HT-58-2 culture is composed of the cyanobacterium and a community of associated bacteria, complicating the question of which organisms make tolyporphins. Elucidation of the cyanobacterial genome revealed an intriguing gene cluster that contains tetrapyrrole biosynthesis genes and a collection of unknown genes, suggesting that the cluster may be responsible for tolyporphin production. Knowledge of the genome and the gene cluster sharply focuses research to identify related cyanobacterial producers of tolyporphins and delineate the tolyporphin biosynthetic pathway.

Phase transition and high‐temperature properties of rare‐earth niobates (LnNbO4, where Ln = La, Dy and Y) were studied in situ at high temperatures using powder X‐ray diffraction and thermal analysis methods. These materials undergo a reversible, pure ferroelastic phase transition from a monoclinic (S.G. I2/a) phase at low temperatures to a tetragonal (S.G. I41/a) phase at high temperatures. While the size of the rare‐earth cation is identified as the key parameter, which determines the transition temperature in these materials, it is the niobium cation which defines the mechanism. Based on detailed crystallographic analysis, it was concluded that only distortion of the NbO4 tetrahedra is associated with the ferroelastic transition in the rare‐earth niobates, and no change in coordination of Nb5+ cation. The distorted NbO4 tetrahedron, it is proposed, is energetically more stable than a regular tetrahedron (in tetragonal symmetry) due to decrease in the average Nb–O bond distance. The distortion is affected by the movement of Nb5+ cation along the monoclinic b‐axis (tetragonal c‐axis before transition), and is in opposite directions in alternate layers parallel to the (010). The net effect on transition is a shear parallel to the monoclinic [100] and a contraction along the monoclinic b‐axis. In addition, anisotropic thermal expansion properties and specific heat capacity changes accompanying the transition in the studied rare‐earth niobate systems are also discussed.