Metal-ion-dependent GFP emission in vivo by combining a circularly permutated green fluorescent protein with an engineered metal-ion-binding coiled-coil

Coordination of metal ions significantly contributes to protein structures and functions. Here we constructed a fusion protein, consisting of a de novo designed, metal-ion-binding, trimeric coiled-coil and a circularly permutated green fluorescent protein (cpGFP), where the fluorescent emission from cpGFP was induced by metal ion coordination to the coiled-coil. A circularly permutated GFP, (191)cpGFP(190), was constructed by connecting the original N- and C-termini of GFP(UV) by a GGSGG linker and cleaving it between Asp(190) and Gly(191). The metal-ion-binding coiled-coil, IZ-HH, was designed to have three alpha-helical structures, with 12 His residues in the hydrophobic core of the coiled-coil structure. IZ-HH exhibited an unfolded structure, whereas it formed the trimeric coiled-coil structure in the presence of divalent metal ions, such as Cu(2+), Ni(2+), or Zn(2+). The fusion protein (191)cpGFP(190)-IZ-HH was constructed, in which (191)cpGFP(190) was inserted between the second and third alpha-helices of IZ-HH. Escherichia coli cells, expressing (191)cpGFP(190)-IZ-HH, exhibited strong fluorescence when the Cu(2+) and Zn(2+) ions were present in the medium, indicating that they passed through the cell membrane and induced the proper folding of the (191)cpGFP(190) domain. This strategy, in which protein function is regulated by a metal-ion-responsive coiled-coil, should be applicable to the design of various metal-ion-responsive, nonnatural proteins that work both in vitro and in vivo.     

Loop-erased random walk on the Sierpinski gasket

In this paper the loop-erased random walk on the finite pre-Sierpiński gasket is studied. It is proved that the scaling limit exists and is a continuous process. It is also shown that the path of the limiting process is almost surely self-avoiding, while having Hausdorff dimension strictly greater than 1. The loop-erasing procedure proposed in this paper is formulated by erasing loops, in a sense, in descending order of size. It enables us to obtain exact recursion relations, making direct use of ‘self-similarity’ of a fractal structure, instead of the relation to the uniform spanning tree. This procedure is proved to be equivalent to the standard procedure of chronological loop-erasure.     

Characterization of hybrid electrolytes prepared from the Li2S-P2S5 glasses and alkanediols

Inorganic-organic hybrid electrolytes were prepared by the mechanochemical method using the Li⁺ ion conductive 70Li₂S·30P₂S₅ glass and various alkanediols. Local structure of the prepared electrolytes was analyzed by FT-IR and Raman spectroscopy. The effects of the proportion and chain length of alkanediols on conductivity of the hybrid electrolytes were investigated. The hybrid electrolyte with 2 mol.% of 1,4-butanediol exhibited the conductivity of 9.7 × 10^− 5 S cm^− 1 at room temperature and the unity of lithium ion transference number. The use of alkanediols with shorter chain length was effective in increasing conductivity of hybrid electrolytes. The electrolyte using ethyleneglycol showed the highest conductivity of 1.1 × 10^− 4 S cm^− 1 at room temperature. Lowering glass transition temperature by incorporation of alkanediols is responsible for the enhancement of conductivity of hybrid electrolytes.     

Remarks on Hölder continuity for solutions of the p-Laplace evolution equations

We study the interior Hölder regularity problem for the gradient of solutions of the p-Laplace evolution equations with the external forces. Misawa gave some conditions for the Hölder continuity of the gradient of solutions. We show Hölder estimates of the solutions with weaker condition as for Misawa.     

Structural diversity and magnetic properties in 1D and 2D azido-bridged cobalt(II) complexes with 1,2-bis(2-pyridyl)ethylene

By utilizing a flexible co-ligand 1,2-bis(2-pyridyl)ethylene (2,2'-bpe), two new azido-bridged cobalt(II) complexes with the formulae [Co?(N?)?(OH?)?(2,2'-bpe)?](n)(2,2'-bpe)(n) (1) and [Co(N?)?(2,2'-bpe)?](n) (2) have been synthesized and structurally characterized. Compound 1 shows an uncommon 1D chain comprised of double EO azido bridged five- and six-coordinated Co(II) geometries in a unique (-5-5-6-)(n) sequence of the coordination number. The 2,2'-bpe acts as a terminal co-ligand and an uncoordinated molecule in the crystal lattice. Moreover the adjacent 1D chain is assembled by C-Hπ interactions and the intermolecular hydrogen bonding between uncoordinated 2,2'-bpe and coordinated water molecules building a 2D layer. Whereas, compound 2 is a 2D coordination network containing the alternating double EO and double EE bridging modes of azides and ditopic 2,2'-bpe bridges. The magnetic investigation of 1 reveals dominant intra-chain ferromagnetic interactions, with the double EO azide-bridge and weak inter-chain antiferromagnetic interactions, with overall metamagnetic behaviour, having magnetic ordering at 6 K. The magnetic behaviour of 2 shows spin-canted antiferromagnetism below a T(N) of 12 K.     

Photoreactivity of crystals of a rhodium dithionite complex with ethyltetramethylcyclopentadienyl ligands: crystal surface morphology changes and degradation

A photoreactive rhodium dithionite complex [(RhCp(Et))(2)(μ-CH(2))(2)(μ-O(2)SSO(2))] (1(Et)) with Cp(Et) (η(5)-C(5)Me(4)Et) ligands was newly synthesized. Upon short-time irradiation with low intensity light, two kinds of stepwise surface morphology changes of the crystal 1(Et) were observed. Prolonged irradiation with high intensity light caused cracking and breaking down of the crystal.     

A convergent synthesis of the C1-C16 segment of goniodomin A via palladium-catalyzed organostannane-thioester coupling

A convergent synthesis of the C1-C16 segment of goniodomin A, an actin-targeting marine polyether macrolide natural product, has been achieved via a 2-fold application of palladium-catalyzed organostannane-thioester coupling.     

Minerals and aligned collagen fibrils in tilapia fish scales: structural analysis using dark-field and energy-filtered transmission electron microscopy and electron tomography

The mineralized structure of aligned collagen fibrils in a tilapia fish scale was investigated using transmission electron microscopy (TEM) techniques after a thin sample was prepared using aqueous techniques. Electron diffraction and electron energy loss spectroscopy data indicated that a mineralized internal layer consisting of aligned collagen fibrils contains hydroxyapatite crystals. Bright-field imaging, dark-field imaging, and energy-filtered TEM showed that the hydroxyapatite was mainly distributed in the hole zones of the aligned collagen fibrils structure, while needle-like materials composed of calcium compounds including hydroxyapatite existed in the mineralized internal layer. Dark-field imaging and three-dimensional observation using electron tomography revealed that hydroxyapatite and needle-like materials were mainly found in the matrix between the collagen fibrils. It was observed that hydroxyapatite and needle-like materials were preferentially distributed on the surface of the hole zones in the aligned collagen fibrils structure and in the matrix between the collagen fibrils in the mineralized internal layer of the scale.     

Compact bipolar plate-free direct methanol fuel cell stacks

Fuel cells with a PtAu/C anode and a Pr-doped Mn(2)O(3)/C cathode were stacked without using a bipolar plate, and their discharge properties were investigated in a methanol aqueous solution bubbled with air. A three-cell stack exhibited a stack voltage of 2330 mV and a power output of 21 mW.     

Anomalous mechanical characteristics of Au/Cu nanocomposite processed by Cu electroplating

An Au/Cu nanocomposite is produced by electroplating Cu on a nanoporous Au, and its mechanical characteristics are investigated by hardness tests. The Au/Cu nanocomposite showed a lower hardness and a lower elastic modulus than the nanoporous Au. Furthermore, annealing caused the nanocomposite to harden twice. Large lattice strains in the Au lattice for the nanocomposite were observed by high-resolution transmission electron microscopy. Also, first-principle calculations showed that lattice strains induce the decreased elastic modulus. Therefore, both the inverse mixing behaviour and the hardening via annealing are suggested to be related to the large lattice strains.