Identification of integrin-dependent and -independent cell adhesion domains in COOH-terminal globular region of laminin-5 alpha 3 chain

Laminin-5 is an isoform of laminin that consists of alpha 3, beta 3, and gamma 2 chains and has potent cell adhesion- and cell migration-promoting activities. In this study, five subdomains in the COOH-terminal globular (G) domain of human laminin alpha 3 chain were individually expressed in Escherichia coli, and their biological activities were investigated. Recombinant G2, G4, and G5 domains promoted adhesion to plastic plates of HT1080 fibrosarcoma cells, A431 epidermoid carcinoma cells, and ECV304 vascular endothelial cells. For the cell adhesion activity, the G2 domain required a divalent cation and heat-sensitive conformation more strongly than G4 and G5. The cell adhesion to G2 but not G4 and G5 was effectively inhibited by an anti-integrin alpha 3 antibody. A cell adhesion sequence of 22 amino acids, alpha 3G2A, that was homologous to the integrin alpha 3 beta 1-binding sequence GD-6 of laminin alpha 1 chain was identified within the G2 structure. The cell adhesion to alpha 3G2A peptide was also inhibited by the anti-integrin alpha 3 antibody. The cell adhesion to G2, alpha 3G2A, G4, and G5 was strongly inhibited by heparin, but that to native laminin-5 was inhibited less effectively. Moreover, G5 potently stimulated chemotactic migration of rat liver epithelial cells in Boyden chambers, but G2 and G4 did not. These results indicate that the G domain of laminin alpha 3 contains multiple cell binding sites with different mechanisms and different functions. The G2 domain seems to recognize integrin alpha 3 beta 1, whereas G4 and G5 may interact with heparin-like molecules on cell surface.     

Thermal properties and characteristics of thin layers of nickel dithiolene complexes

Thermal properties of near infra–red–absorbing nickel dithiolene complexes have been examined by thermal gravimetric and differential scanning calorimetry analysis. The nickel complexes with relatively low melting points gave a DRAW disc with better recording characteristics, when they were used as inhibitors of the photofading of thin layers of cyanine dyes. Thin layers of the nickel complexes on polymethylmethacrylate or glass were formed by spin coating and by the radio–frequency reactive ion plating technique. Their reflectance, absorption spectra and optical recording characteristics have been recorded.     

Electrical Electron Spin Injection with a p+-(Ga,Mn)As/n+-GaAs Tunnel Junction

We demonstrate electrical electron spin injection in a p⁺-(Ga,Mn)As/n⁺-GaAs tunnel junction with an n-GaAs/(In,Ga)As/p-GaAs light emitting diode (LED). By applying a reverse bias to the p⁺-(Ga,Mn)As/n⁺-GaAs junction (forward bias to the LED), we observed clear hysteresis in electroluminescence (EL) polarization. The magnitude of the EL polarization, which does not depend critically on the spacer layer thickness up to 800 nm, is found to be about five times greater than that of the hole spin injection.     

Effect of a vacuum-deposited metal film on the CV of the Li insertion/extraction reaction at a graphitized carbon fiber electrode

A metal film of silver, copper, or gold was vacuum-deposited on the surface of mesophase pitch-based carbon fiber prepared at 3100 °C, and the Li insertion/extraction behaviour was examined by measuring the cyclic voltammogram (CV) for various film thicknesses in a non-aqueous electrolyte containing 1 M LiClO₄. The peak height of the CV was examined in detail for the deposited silver film. The peak height increased at first with increasing film thickness up to 150 Å, but then began to decrease. At around 200 Å, a minimum peak height which was nearly the same as that of the pristine sample was observed. The peak height then increased again up to a film thickness of 400 Å, where it was two times higher than that of pristine sample, then decreased gradually. Such a complicated CV could not be observed with a gold or copper film where the enhancing effect was monotonous and more remarkable with a thinner film. X-ray diffraction patterns of the silver film deposited on the carbon fiber showed a strong crystal orientation to the carbon substrate like epitaxial growth, which was found to be dependent on both the thickness and the deposition rate. The CV peak height correlated well with the silver crystal orientation, implying that the electrochemical reaction rate differs on different crystal faces. Such could not be found in the case of gold or copper. The peak enhancing effect and the cycle behaviour were elucidated in view of the nature of solid electrolyte interphase (SEI), conductivity, and the effect of alloy formation.     

Dispersion Stability of O/W Emulsions with Different Oil Contents Under Various Freezing and Thawing Conditions

Freezing and thawing of oil‐in‐water (O/W) emulsion‐type foods bring about oil–water separation and deterioration; hence, the effects of freezing and thawing conditions on the destabilization of O/W emulsions were examined. The freezing rate and thawing temperature hardly affected the stability of the O/W emulsion. O/W emulsions having different oil fractions were stored at temperatures ranging from –30 to –20 °C and then thawed. The stability after thawing depended on the storage temperature, irrespective of the oil fraction of the emulsion. A good correlation was found between the time at which the stability began to decrease and the time taken for the oil to crystalize. These results indicated that the dominant cause for the destabilization of the O/W emulsion during freezing and thawing is the crystallization of the oil phase and that the effects of the freezing and thawing rates on the stability are insignificant.     

Central Nervous System Stimulants Limit Caffeine Transport at the Blood–Cerebrospinal Fluid Barrier

Caffeine, a common ingredient in energy drinks, crosses the blood–brain barrier easily, but the kinetics of caffeine across the blood–cerebrospinal fluid barrier (BCSFB) has not been investigated. Therefore, 127 autopsy cases (Group A, 30 patients, stimulant-detected group; and Group B, 97 patients, no stimulant detected group) were examined. In addition, a BCSFB model was constructed using human vascular endothelial cells and human choroid plexus epithelial cells separated by a filter, and the kinetics of caffeine in the BCSFB and the effects of 4-aminopyridine (4-AP), a neuroexcitatory agent, were studied. Caffeine concentrations in right heart blood (Rs) and cerebrospinal fluid (CSF) were compared in the autopsy cases: caffeine concentrations were higher in Rs than CSF in Group A compared to Group B. In the BCSFB model, caffeine and 4-AP were added to the upper layer, and the concentration in the lower layer of choroid plexus epithelial cells was measured. The CSF caffeine concentration was suppressed, depending on the 4-AP concentration. Histomorphological examination suggested that choroid plexus epithelial cells were involved in inhibiting the efflux of caffeine to the CSF. Thus, the simultaneous presence of stimulants and caffeine inhibits caffeine transfer across the BCSFB.     

New fabrication technique of conductive polymer/insulating polymer composite films and evaluation of biocompatibility in neuron cultures

Poly(vinyl alcohol), PVA, produces a flexible composite polymer film with electrical, optical and electrochemical properties very similar to those of polypyrrole (PPy). The rate of electrochemical polymerization depends on the diffusion rate of the electrolyte across the PVA film to the indium tin oxide (ITO) electrode. In particular, a solvent with a hydrophilic nature easily penetrates into the PVA film. By applying this new process, we demonstrate a unique method of forming an electrically conductive pattern in PVA film. It will be possible to develop electrodes for electrical stimulation of the nervous system using the conducting polymer, PPy. Then, by applying a similar technique, we fabricated poly(3,4-ethylenedioxythiophene), PEDOT/PVA, composite films and investigated their basic electrochemical properties. Moreover, in this study, in order to develop a novel cell-culture system which makes it possible to communicate with cultured cells, fibroblasts were cultured on PPy- and PEDOT-coated ITO conductive glass plates for 7 days. The result reveals that the PPy and PEDOT films support the secretory functions of the cells cultured on its surface. The PPy- and PEDOT-coated electrodes may be useful to culture the cells on.     

Guided Molecular Assembly on a Locally Reactive 2D Material

Atomically precise engineering of the position of molecular adsorbates on surfaces of 2D materials is key to their development in applications ranging from catalysis to single‐molecule spintronics. Here, stable room‐temperature templating of individual molecules with localized electronic states on the surface of a locally reactive 2D material, silicene grown on ZrB₂, is demonstrated. Using a combination of scanning tunneling microscopy and density functional theory, it is shown that the binding of iron phthalocyanine (FePc) molecules is mediated via the strong chemisorption of the central Fe atom to the sp³‐like dangling bond of Si atoms in the linear silicene domain boundaries. Since the planar Pc ligand couples to the Fe atom mostly through the in‐plane d orbitals, localized electronic states resembling those of the free molecule can be resolved. Furthermore, rotation of the molecule is restrained because of charge rearrangement induced by the bonding. These results highlight how nanoscale changes can induce reactivity in 2D materials, which can provide unique surface interactions for enabling novel forms of guided molecular assembly.