Magnetic model for a horse-spleen ferritin with a three-phase core structure

The increasing interests in magnetic nanoparticles has prompted research on ferritin, which is naturally a well-defined iron-storage protein in most living organisms. However, the exact magnetic behavior of ferritin is not well understood, because the crystal structures of ferritin and ferrihydrite, its major component, are not fully understood. Briefly, we discuss the previous magnetization models of ferritin and ferrihydrite and we present a new model (Σ3L) of the initial magnetization of ferritin, considering its different phases. The new model includes three Langevin-function terms, which represent three different magnetic moments provided by the likely hydroxide and oxide mineral phases in ferritin. Compared to previous models, our simple model fits the experimental data 12 times better in terms of the sum of least squares. The magnetic independence of each component supports the multi-phase compositional model of the mineral core of horse-spleen ferritin. This Σ3L model gives a quantization of the amounts of the different phases within horse-spleen ferritins that matches other published experimental data: 60-80% ferrihydrite, 15-25% maghemite/magnetite, and 1-10% hematite.     

Hydrogen-Bond Structure and Low-Frequency Dynamics of Electrolyte Solutions: Hydration Numbers from ab Initio Water Reorientation Dynamics and Dielectric Relaxation Spectroscopy

We present an atomistic simulation scheme for the determination of the hydration number (h) of aqueous electrolyte solutions based on the calculation of the water dipole reorientation dynamics. In this methodology, the time evolution of an aqueous electrolyte solution generated from ab initio molecular dynamics simulations is used to compute the reorientation time of different water subpopulations. The value of h is determined by considering whether the reorientation time of the water subpopulations is retarded with respect to bulk-like behavior. The application of this computational protocol to magnesium chloride (MgCl₂) solutions at different concentrations (0.6–2.8 mol kg⁻¹) gives h values in excellent agreement with experimental hydration numbers obtained using GHz-to-THz dielectric relaxation spectroscopy. This methodology is attractive because it is based on a well-defined criterion for the definition of hydration number and provides a link with the molecular-level processes responsible for affecting bulk solution behavior. Analysis of the ab initio molecular dynamics trajectories using radial distribution functions, hydrogen bonding statistics, vibrational density of states, water-water hydrogen bonding lifetimes, and water dipole reorientation reveals that MgCl₂ has a considerable influence on the hydrogen bond network compared with bulk water. These effects have been assigned to the specific strong Mg-water interaction rather than the Cl-water interaction.     

Investigation of the effects of graphite flake alignment on thermal emissivity by applying a magnetic field during coating of an aluminum sheet

In this study we investigated the effects of graphite flake alignment on thermal emissivity by applying a magnetic field during coating of aluminum sheets with graphite. The coating paste was prepared by ball milling graphite flakes with an organic binder. The graphite flake content was 9.1, 13.0, 16.7, 20.0, or 23.1 wt.%. After coating of aluminum sheets with the paste by dipping, a magnetic field was applied vertically to the coated aluminum sheet by use of neodymium magnets. It was observed that the graphite flakes were aligned at an angle to the surface by application of the magnetic field. In contrast, in the absence of the magnetic field the graphite flakes were aligned horizontally on the aluminum sheets. The surface roughness of specimens prepared by use of a magnetic field (MF; R _a = 10.172–14.654 μm) was more than twofold that of specimens for which no magnetic field was applied (NMF; R _a = 4.564 μm). The thermal emissivity of MF9 (9.1 wt.% graphite; ε = 0.80) was higher than that of NMF9 (9.1 wt.% graphite; ε = 0.77). The thermal emissivity of MF20 (20.0 wt.% graphite) was 0.91, the highest in this study. It was shown that flakes aligned at an angle to the surface contribute to enhanced thermal emissivity. Well aligned graphite flakes are therefore expected to enable high thermal dissipation from electronic components.     

In situ detection of live cancer cells by using bioprobes based on Au nanoparticles

We fabricate the high-performance probes based on Au nanoparticles (AuNP) for detection of live cancer cell. AuNP were synthesized with narrow sized distribution (ca. 10 nm) by Au salt reduction method and deposited onto the aminated substrate as a cross-linker and hot spot. Herein, AuNP has enabled the easy and efficient immobilization of the antibody (Cetuximab), which can selectively interact with epidermal growth factor receptor (EGFR) on the surface of epidermal cancer, as detecting moiety onto the AuNP-deposited substrate without nanolithography process. After conjugation of Cetuximab with AuNP-deposited substrate, Cetuximab-conjugated probe as a live cancer cell detector (LCCD) could detect EGFR-highexpressed A431 cells related to epithelial cancer with 54-times larger specificity and sensitivity in comparison with EGFR-deficient MCF7 cells. This implies that AuNP-based probes demonstrate abundant potentials for detection and separation of small biomolecules, cells and other chemicals.     

Effect of fused thiazolothiazole on the photovoltaic performance of fluorene-thiazole-based conjugated polymers

In this work, we utilized two fluorene-based polymers (F8TBTT and F8TTZT) as donor materials in organic photovoltaic cells (OPVs) and compared their performance to explain the effect of substituting fused thiazolothiazole for the bithiazole moiety. The OPV device based on F8TTZT showed a power conversion efficiency of 0.24%, which is three times higher than that of F8TBTT (0.07%) under the same conditions. The better performance can be explained by the increased planarity and enhanced intermolecular charge transport.     

Ring closure reaction dynamics of diarylethene derivatives in solution

Photochromic ring closure reaction dynamics of 1,2-bis(2-methylbenzo[b]thiophen-3-yl)hexafluoro cyclopentene and its derivatives in solution has been studied by femtosecond time-resolved fluorescence. Time-resolved spontaneous fluorescence of the open isomer reveals a fast component of around 1 ps and a slow component on the order of 100 ps. Fluorescence time profiles, reaction quantum yields, and relative populations of the parallel (C(s) symmetry) and antiparallel (C(2) symmetry) conformations indicate that both time components are attributable mostly to the C(2) conformer that undergoes the ring closure reaction. The fast component is assigned to the direct ring closure reaction, and the slow component is assigned to the reaction through conformation change. Time constants of the slow component for the derivatives are inversely proportional to the reaction quantum yields, suggesting that the rate of the conformational dynamics is comparable to the rate of other population relaxation processes. The relative amplitude and exact time constant of the fast component depend on the detection wavelength displaying a higher relative amplitude with shorter time constant at longer wavelengths. The results allow us to propose a conformational inhomogeneity model, in which a broad distribution of conformations of the open isomers in the ground state is projected into two minima in the excited electronic potential surface to lead to the slow and the fast reaction pathways.     

Simultaneous Quantification of 3′- and 6′-Sialyllactose in Rat Plasma Using Liquid Chromatography-Tandem Mass Spectrometry and Its Application to a Pharmacokinetic Study

Sialyllactose (SL), an acidic oligosaccharide, has immune-protective effects against pathogens and helps with the development of the immune system and intestinal microorganisms. To elucidate the pharmacokinetic characterization after oral administration to rats, the simultaneous quantification method for 3′-SL and 6′-SL in rat plasma was validated, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in an electrospray ionization (ESI) mode. Several types of columns [C18, amide, and hydrophilic interaction liquid chromatography (HILIC) phase] were used to separate the peaks of 3′-SL and 6′-SL, which improved chromatographic selectivity. Ultimately, the HILIC phase column had a good peak shape and quick resolution, with a mobile phase comprising ammonium acetate buffer and acetonitrile obtained by gradient elution. In addition, the simultaneous quantification of 3′-SL and 6′-SL in rat plasma samples were adequately applied to pharmacokinetic study.     

A colorimetric and fluorescent chemosensor for detection of Hg2+ using counterion exchange of cationic polydiacetylene

In this study, a colorimetric and fluorescent chemosensor for mercury ions (Hg²⁺) was developed. Cationic polydiacetylene (PDA) vesicles with a quaternary ammonium cation and iodide as a counterion show a blue-to-red color transition; the color change is accompanied by a fluorescence enhancement in selective response to Hg²⁺ ions because of a perturbation of the ene–yne conjugated backbone induced by counterion exchange. It allows for selective detection of Hg²⁺ with the naked eye and the sensor is used to determine Hg²⁺ concentrations in tap water samples.     

A Hollow Foldecture with Truncated Trigonal Bipyramid Shape from the Self‐Assembly of an 11‐Helical Foldamer

The creation of self‐assembling microscale architectures that possess new and useful physical properties remains a significant challenge. Herein we report that an 11‐helical foldamer self‐assembles in a controlled manner to form a series of 3D foldectures with unusual three‐fold symmetrical shapes that are distinct from those generated from 12‐helical foldamers. The foldamer packing motif was revealed by powder X‐ray diffraction technique, and provides an important link between the molecular‐level symmetry and the microscale morphologies. The utility of foldectures with hollow interiors as robust and well‐defined supramolecular hosts was demonstrated for inorganic, organic, and even protein guests. This work will pave the way for the design of functional foldectures with greater 3D shape diversity and for the development of biocompatible delivery vehicles and containment vessels.     

A triazine compound S06 inhibits proinvasive crosstalk between carcinoma cells and stromal fibroblasts via binding to heat shock protein 90

Carcinoma-associated fibroblasts (CAFs) promote tumor invasion by secreting soluble factors. A tagged triazine library was screened in our novel transwell coculture model of CAF and oral squamous cell carcinoma (OSCC). We discovered compound S06, which reduced OSCC invasion by inhibiting secretion of CAF-derived proinvasive chemokines. The N-terminus of Hsp90 was found to be the cellular target of S06. Importantly, S06 did not induce hepatic toxicity, a side effect associated with well-known Hsp90 inhibitors. Moreover, S06 inhibited tumor cell migration in a zebrafish xenograft model. Our results demonstrate that Hsp90 is a novel target for stromal-based therapy to modulate proinvasive molecular crosstalk within the tumor microenvironment. Furthermore, S06 represents a new class of Hsp90 inhibitor and is an attractive candidate for anticancer drug development.