Electric field-associated deformation of polyelectrolyte gel near a phase transition point

The influence of de electric fields on sodium acrylate—acrylamide copolymer gel near a phase transition point in acetone—water mixtures containing NaOH was studied. In the mixtures free of NaOH, the shrunken-state gel near a phase transition point was not influenced by dc electric fields, while the swollen-state gel near it shrank from its part facing to the positive electrode in dc electric fields. In the presence of NaOH, unprecedented swelling of the shrunken-state gel has been observed. The swollen-state gel showed swelling or shrinking in the field. The type of deformation was determined by the concentration of NaOH. The drift of mobile ions played a role in the deformation. The shrinking occurred through the conformational change of polymer network caused by the drift. The swelling was observed by the change of the osmotic pressure based upon the ion concentration difference between the inside and the outside of a gel.     

Preparation of polydiacetylene single crystals based on physical vapor growth technique

We have succeeded in obtaining 10-mm-size polydiacetylene (PDA) single crystals using the physical vapor growth technique followed by the irradiation of ultraviolet (UV) rays, for the first time. The variety of growth conditions, such as growth temperature, growth time, carrier gases, and flow rate of gases are examined. Especially, the growth temperature and growth time have clear effects on the quality of crystals. Morphologies and sizes with relation to the various growth conditions are also observed. They show only one type of plateletlike shape with a pair of large parallelopiped planes, regardless of variety of growth conditions. The crystal thickness was estimated as about 500 nm by the observation of atomic force microscopy. The solubility of diacetylene (DA) and PDA to some organic solvents, and the X-ray diffraction data indicate that the obtained crystals are single crystals.     

Development of a High-Affinity Antibody-Binding Peptide for Site-Specific Modification

Immunoglobulin G (IgG)-binding peptides such as 15-IgBP are convenient tools for the site-specific modification of antibodies and the preparation of homogeneous antibody–drug conjugates. A peptide such as 15-IgBP can be selectively crosslinked to the fragment crystallizable region of human IgG in an affinity-dependent manner via the ϵ-amino group of Lys8. Previously, we found that the peptide 15-Lys8Leu has a high affinity (K_d=8.19 nM) due to the presence of the γ-dimethyl group in Leu8. The primary amino group required for the crosslinking to the antibodies has, however, been lost. Here, we report the design and synthesis of a novel unnatural amino acid, 4-(2-aminoethylcarbamoyl)leucine (Aecl), which possesses both the γ-dimethyl fragment and a primary amino group. A peptide containing Aecl8 (15-Lys8Aecl) was synthesized and showed a binding affinity ten times higher (K_d=24.3 nM) than that of 15-IgBP (K_d=267 nM). Fluorescein isothiocyanate (FITC)-labeled 15-Lys8Aecl with an N-hydroxy succinimide ester at the side chain of Aecl8 (FITC-15-Lys8Aecl(OSu)) successfully labeled an antibody (trastuzumab, Herceptin^®) with the fluorophore. This peptide scaffold has both strong binding affinity and crosslinking capability, and could be a useful tool for the selective chemical modification of antibodies with molecules of interest such as drugs.     

Development of amperometric immunosensor using boron-doped diamond with poly(o-aminobenzoic acid)

An alternative method of a protein immunosensor has been developed at boron-doped diamond (BDD) electrode material. In order to construct the base of the immunosensor, o-aminobenzoic acid (o-ABA) was electropolymerized at an electrode by cyclic voltammetry. The poly-o-ABA-modified BDD was characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The XPS result found that carboxyl groups were formed at the electrode surface. The carboxyl groups were then used to covalently attach protein probes. The amperometric sensing of mouse IgG (MIgG) was selected as the model at the poly-o-ABA-modified BDD to compare to the poly-o-ABA-modified glassy carbon (GC) at the same condition. An antimouse IgG from goat (GaMIgG) was covalently immobilized at a poly-o-ABA-modified BDD electrode which used a sandwich-type alkaline phosphatase (ALP) catalyzing amperometric immunoassay with 2-phospho-L-ascorbic acid (AAP) as substrate. The ALP enzyme conjugated at the immunosensor can generate AAP to the electroactive species of ascorbic acid (AA), which can be determined by amperometric detection. The signal was found to be proportional with the quantity of MIgG. The limits of detection (LODs) of 0.30 (3 SD) and 3.50 ng mL(-1) (3 SD) for MIgG at BDD and GC electrodes were obtained. It also was found that the dynamic range of 3 orders of magnitude (1-1000 ng mL(-1)) was obtained at BDD, whereas at GC, the dynamic range was more narrow (10-500 ng mL(-1)). The method was applied to a real mouse serum sample that contains MIgG.     

Expression and Prognostic Significance of CD47–SIRPA Macrophage Checkpoint Molecules in Colorectal Cancer

Despite the confirmed anti-cancer effects of T-cell immune checkpoint inhibitors, in colorectal cancer (CRC) they are only effective in a small subset of patients with microsatellite-unstable tumors. Thus, therapeutics targeting other types of CRCs or tumors refractory to T-cell checkpoint inhibitors are desired. The binding of aberrantly expressed CD47 on tumor cells to signal regulatory protein-alpha (SIRPA) on macrophages allows tumor cells to evade immune destruction. Based on these observations, drugs targeting the macrophage checkpoint have been developed with the expectation of anti-cancer effects against T-cell immune checkpoint inhibitor-refractory tumors. In the present study, 269 primary CRCs were evaluated immunohistochemically for CD47, SIRPA, CD68, and CD163 expression to assess their predictive utility and the applicability of CD47–SIRPA axis-modulating drugs. Thirty-five percent of the lesions (95/269) displayed CD47 expression on the cytomembrane of CRC cells. CRCs contained various numbers of tumor-associated immune cells (TAIs) with SIRPA, CD68, or CD163 expression. The log-rank test revealed that patients with CD47-positive CRCs had significantly worse survival than CD47-negative patients. Multivariate Cox hazards regression analysis identified tubular-forming histology (hazard ratio (R) = 0.23), age < 70 years (HR = 0.48), and high SIRPA-positive TAI counts (HR = 0.55) as potential favorable factors. High tumor CD47 expression (HR = 1.75), lymph node metastasis (HR = 2.26), and peritoneal metastasis (HR = 5.80) were cited as potential independent risk factors. Based on our observations, CD47–SIRPA pathway-modulating therapies may be effective in patients with CRC.     

Double Charge Polarity Switching in Sb-Doped SnSe with Switchable Substitution Sites

Tin mono-selenide (SnSe) is one of the most promising thermoelectric materials; however, it experiences difficulty in controlling the carrier polarity, which is inevitable for realizing p-n homojunction devices. Herein, double switching of charge polarity in (Sn_1−xSb_x)Se by varying x is reported; pure SnSe shows p-type conduction, whereas the polarity of (Sn_1−xSb_x)Se switches to n-type conduction for 0.005 < x < 0.05, and then re-switches to p-type conduction for x > 0.05. The major Sb substitution site switches from the Se (Sb_Se) to Sn site (Sb_Sn) with increasing x. Sb_Sn (Sb³⁺ at Sn²⁺) works as a donor, but Sb_Se (Sb³⁻ at Se²⁻) does not produce a hole because of the Sb–Sb dimer formation. The mechanism of double polarity switching is explained by native p-type conduction in pure SnSe due to Sn-vacancy formation, whereas (Sn_1−xSb_x)Se exhibits n-type behavior due to conduction through the Sb_Se impurity band formed above the valence band maximum, and finally re-switches to weak p-type, where the Fermi level approaches the midgap level between the Sb_Se band and conduction band minimum. Clarification of the Sb doping mechanism will provide a crucial guide for developing more sophisticated doping routes for SnSe and high-performance energy-related devices.     

Single-crystal solidification of new Co–Al–W-base alloys

Solidification processing of new high-temperature Co–Al–W-base single-crystals has been investigated. Single-crystal bars with compositions of Co–9.4Al–10.7W, Co–8.8Al–9.8W–2Ta and Co–7.8Al–7.8W–1.5Ta–4.5Cr (at%) were successfully grown with a conventional Bridgman process. Helical grain selectors resulted in [001] dendritic growth with primary dendrite arm spacings in the range of 278–364 μm. Segregation of constituent elements in the dendritic structure was very limited, compared to Ni-base single-crystals. Concentration profiles obtained by electron microprobe and analyzed via the Scheil equation indicate distribution coefficients for Co, Al, W and Cr that are close to 1. The distribution coefficient of Ta was approximately 0.6, indicating preferential segregation to the liquid during solidification. These observations collectively suggest that convective instabilities and freckle formation are unlikely to occur during solidification of single-crystals of this new class of high strength Co–Al–W-base alloys.     

The Influence of Rh Addition on the Catalytic Activity of Cubic Pt Nanocrystals Supported on Alumina for NO/CH4 Reaction

The effect of the Rh addition to the well defined cubic (≈70%) Pt nanocrystals of around 13 nm supported on alumina was investigated for NO/CH₄ reaction. The impact of size and shape of Pt nanoparticles on the catalytic activity were also analyzed by comparing the results with a conventionally prepared catalyst.     

Self‐Activated Vanadate Compounds Toward Realization of Rare‐Earth‐Free Full‐Color Phosphors

Rare‐earth‐free phosphors based on vanadate compounds were investigated, where the vanadates included chloride vanadates (M^II₂VO₄Cl), pyrovanadates (M^II₂V₂O₇), orthovanadates (M^II₃(VO₄)₂) with divalent cations M^II of Mg, Sr, Ba, and Zn, and oxofluorovanadates (A^IVOF₄) with an alkali metal A^I. A chloride pyrolysis method and a liquid phase precipitation method were proposed for preparing the chloride vanadates and pyro‐ and orthovanadates, respectively. These vanadate compounds showed self‐activated photoluminescence (PL) based on the VO₄ clusters against the ultraviolet (UV) light irradiation. The colors of PL covered almost the whole visible‐light region from blue to yellow as Sr₂VO₄Cl (deep blue), Ca₂VO₄Cl (sky blue), Ba₂V₂O₇ (green), Sr₂V₂O₇ (yellowish green), Zn₃(VO₄)₂ (yellow), and Mg₃(VO₄)₂ (yellow). A correlation was suggested from these compounds between the luminescent colors and the structural feature as the longer V–O distances in the VO₄ tetrahedra in the crystal structures led to the longer wavelength in PL. This seemed to be also applicable for the oxofluorovanadates A^IVOF₄ (A^I = K and Cs) which contain the VOF₄ polyhedra with one O^2? ion and four F^‐ ions as the ligands, as they exhibited the reddish PL.