A complete classification of continuous fractional operations on $$\mathbb {C}$$ C

Periodica Mathematica Hungarica - We completely classify continuous fractional operations on the complex number field $$\mathbb {C}$$ modulo equivalence. A continuous fraction is described by a...     

Novel sequential 1,4-Brook rearrangement-Wittig reaction: new one-pot approach for silyl dienol ethers

A novel one-pot synthetic method of silyl dienol ethers via 1,4-Brook rearrangement-Wittig reaction sequence has been developed. This tandem reaction proceeded via the intramolecular silyl migration step, which enabled stereoselective formation of phosphorane intermediates. The reaction is operationally simple and high yielding, thus providing a new useful formula for silyl dienol ether synthesis.     

Double-Layered Metal Mesh Film With Limited Viewing Angle Prepared by Electroless Plating of Self-Organized Honeycomb Film

We have reported that honeycomb-like porous polymer films, which were spontaneously formed in the casting of polymer solutions under humid conditions, were converted into honeycomb-like metal meshes by electroless plating. In this report, the unique optical properties of these meshes will be discussed. Silver-coated honeycomb mesh films were prepared by selforganization and electroless plating methods. The incident angle dependence of their transparency, and their electrical conductivity were measured. The metallized film had limited viewing angle.     

Efficient parametric excitation walking with delayed feedback control

In passive dynamic walking proposed by McGeer, mechanical energy lost by heel strike is restored by transporting potential energy to kinetic energy as walking down a slope. When energy input is larger as a slope is steeper, the bifurcation of a walking cycle occurs. In the parametric excitation walking, which is to realize passive dynamic-like walking on the level ground, the bifurcation of a walking cycle has also been observed when walking speed is fast. Recently, Asano et al. have shown that bifurcation exerts an adverse influence upon walking performance by using a rimless wheel model. In this paper, we apply the delayed feedback control (DFC), originally used in chaos control, to parametric excitation walking to suppress bifurcation. We show in numerical simulation that the proposed method makes period-two walking to period-one walking, and improves energy efficiency. In addition, the proposed method can generate a sustainable gait in the region where a biped robot cannot walk without DFC. The analyses using a Poincaré map reveal that period-one walking with DFC corresponds to an unstable periodic orbit and reveal that a robot model in this paper satisfies the sufficient condition of applicability of DFC.     

Influence of groove depth and surface profile on fluorescence enhancement by grating-coupled surface plasmon resonance

The fluorescence intensity of a sample placed on a metal grating pattern is enhanced due to excitation by the electric field of the grating-coupled surface plasmon resonance (GC-SPR). The dependence of the enhancement on groove depth and surface profile was studied with the aim of improving the sensitivity of fluorescence detection. The enhancement was found to depend on the groove depth, with intensity most enhanced on grating substrate of about 20 nm depth, which produced an intensity about 30 times greater than that on a flat borosilicate glass substrate. Rigorous coupled wave analysis calculation showed that the shape of the groove influenced GC-SPR, suggesting that controlling not only the depth but also the shape of the grating surface profile can be an important factor in improving the sensitivity of detection by fluorescence microscopy.     

Organic Ligand Binding by a Hydrophobic Cavity in a Designed Tetrameric Coiled‐Coil Protein

The design and characterization of a hydrophobic cavity in de novo designed proteins provides a wide range of information about the functions of de novo proteins. We designed a de novo tetrameric coiled‐coil protein with a hydrophobic pocketlike cavity. Tetrameric coiled coils with hydrophobic cavities have previously been reported. By replacing one Leu residue at the a position with Ala, hydrophobic cavities that did not flatten out due to loose peptide chains were reliably created. To perform a detailed examination of the ligand‐binding characteristics of the cavities, we originally designed two other coiled‐coil proteins: AM2, with eight Ala substitutions at the adjacent a and d positions at the center of a bundled structure, and AM2W, with one Trp and seven Ala substitutions at the same positions. To increase the association of the helical peptides, each helical peptide was connected with flexible linkers, which resulted in a single peptide chain. These proteins exhibited CD spectra corresponding to superhelical structures, despite weakened hydrophobic packing. AM2W exhibited binding affinity for size‐complementary organic compounds. The dissociation constants, K_d, of AM2W were 220 nM for adamantane, 81 μM for 1‐adamantanol, and 294 μM for 1‐adamantaneacetic acid, as measured by fluorescence titration analyses. Although it was contrary to expectations, AM2 did not exhibit any binding affinity, probably due to structural defects around the designed hydrophobic cavity. Interestingly, AM2W exhibited incremental structure stability through ligand binding. Plugging of structural defects with organic ligands would be expected to facilitate protein folding.     

Minocycline‐Based Europium(III) Chelate Complexes: Synthesis,Luminescent Properties,and Labeling to Streptavidin

Two chelate ligands for europium(III) having minocycline (=(4S,4aS,5aR,12aS)‐4,7‐bis(dimethylamino)‐1,4,4a,5,5a,6,11,12a‐octahydro‐3,10,12,12a‐tetrahydroxy‐1,11‐dioxonaphthacene‐2‐carboxamide; 5 ) as a VIS‐light‐absorbing group were synthesized as possible VIS‐light‐excitable stable Eu³⁺ complexes for protein labeling. The 9‐amino derivative 7 of minocycline was treated with H₆TTHA (=triethylenetetraminehexaacetic acid=3,6,9,12‐tetrakis(carboxymethyl)‐3,6,9,12‐tetraazatetradecanedioic acid) or H₅DTPA (=diethylenetriaminepentaacetic acid=N,N‐bis{2‐[bis(carboxymethyl)amino]ethyl}glycine) to link the polycarboxylic acids to minocycline. One of the Eu³⁺ chelates, [Eu³⁺(minocycline‐TTHA)] ( 13 ), is moderately luminescent in H₂O by excitation at 395 nm, whereas [Eu³⁺(minocycline‐DTPA)] ( 9 ) was not luminescent by excitation at the same wavelength. The luminescence and the excitation spectra of [Eu³⁺(minocycline‐TTHA)] ( 13 ) showed that, different from other luminescent Eu^III chelate complexes, the emission at 615 nm is caused via direct excitation of the Eu³⁺ ion, and the chelate ligand is not involved in the excitation of Eu³⁺. However, the ligand seems to act for the prevention of quenching of the Eu³⁺ emission by H₂O. The fact that the excitation spectrum of [Eu³⁺(minocycline‐TTHA)] is almost identical with the absorption spectrum of Eu³⁺ aqua ion supports such an excitation mechanism. The high stability of the complexes of [Eu³⁺(minocycline‐DTPA)] ( 9 ) and [Eu³⁺(minocycline‐TTHA)] ( 13 ) was confirmed by UV‐absorption semi‐quantitative titrations of H₄(minocycline‐DTPA) ( 8 ) and H₅(minocycline‐TTHA) ( 12 ) with Eu³⁺. The titrations suggested also that an 1 : 1 ligand Eu³⁺ complex is formed from 12 , whereas an 1 : 2 complex was formed from 8 minocycline‐DTPA. The H₅(minocycline‐TTHA) ( 12 ) was successfully conjugated to streptavidin (SA) (Scheme 5), and thus the applicability of the corresponding Eu³⁺ complex to label a protein was established.