Orientation Control of Photo‐Immobilized Antibodies on the Surface of Azobenzene‐Containing Polymers by the Introduction of Functional Groups

In our photo‐induced immobilization technique for an antibody (IgG) using azopolymers, the introduction of COOH and NMe₂ into the azopolymers, which can introduce surface charges, strongly affected the immobilization properties such as the efficiency of immobilization and the activity of the immobilized IgG (i.e., the orientation of the immobilized IgG). The introduction of COOH promoted a more active orientation of the immobilized IgG. The orientation was determined during the adsorption process onto the azopolymer surface in solution before photo‐immobilization, and was maintained during the photo‐immobilization. The surface charge of the azopolymer appears to be an important factor for IgG orientation, which involves electrostatic interactions between its Fab and the azopolymer surface.

     

Mechanism of the decrease in catalytic activity of human cytochrome P450 2C9 polymorphic variants investigated by computational analysis

Cytochrome P450 (CYP) is deeply involved in the metabolism of chemicals including pharmaceuticals. Therefore, polymorphisms of this enzyme have been widely studied to avoid unfavorable side effects of drugs in chemotherapy. In this work, we performed computational analysis of the mechanism of the decrease in enzymatic activity for three typical polymorphisms in CYP 2C9 species: *2, *3, and *5. Based on the equilibrated structure obtained by molecular dynamics simulation, the volume of the binding pocket and the fluctuation of amino residues responsible for substrate holding were compared between the wild type and the three variants. Further docking simulation was carried out to evaluate the appropriateness of the binding pocket to accommodate substrate chemicals. Every polymorphic variant was suggested to be inferior to the wild type in enzymatic ability from the structural viewpoint. F‐G helices were obviously displaced outward in CYP2C9*2. Expansion of the binding pocket, especially the space near F′ helix, was remarkable in CYP2C9*3. Disappearance of the hydrogen bond between K helix and β4 loop was observed in CYP2C9*5. The reduction of catalytic activity of those variants can be explained from the deformation of the binding pocket and the consequent change in binding mode of substrate chemicals. The computational approach is effective for predicting the enzymatic activity of polymorphic variants of CYP. This prediction will be helpful for advanced drug design because calculations forecast unexpected change in drug efficacy for individuals. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Near-infrared emission bands of Er-doped YAP and LSO crystals

The ground state absorption (GSA), photoluminescence (PL) and photoluminescence excitation (PLE) spectra for Er(1.0 at%):YAP and Er(0.5 at%):LSO were measured at room temperature. Based on the GSA spectra, the radiative transition rates and luminescence branch ratios of erbium ions were determined by the Judd-Ofelt (J-O) method. In the range of 1400-1700 nm Er(1.0 at%):YAP has intense absorption at 1509 nm (0.96×10⁻²⁰ cm²), which is almost two times larger than the peak absorption of Er(0.5 at%):LSO. From the PL and PLE spectra, four intense emission bands around 850 nm (⁴S_3/2→⁴I_13/2), 980 nm (⁴I_11/2→⁴I_15/2), 1230 nm (⁴S_3/2→⁴I_11/2) and 1520 nm (⁴I_13/2→⁴I_15/2) were observed. The stimulated emission cross-sections of the four bands were calculated by the Fuchtbauer-Ladenberg (F-L) equation. The results suggest that Er(1.0 at%):YAP has potential to realize laser oscillation at 858 nm because of the relatively large simulated emission cross-section (1.76×10⁻²⁰ cm²). The temperature dependences of the PL spectra for the two crystals were also investigated in the range of 290-12 K. The ∼1520 nm emission presents continuous increase with temperature, while the emissions around 850, 1230 and 980 nm firstly increase with temperature, then reach their own largest values at the transition temperatures (about 100 K), and finally decrease with temperature. These results were well interpreted by the temperature dependence of multi-phonon process.     

Diagonal composite order in a two-channel Kondo lattice

A novel type of symmetry breaking is reported for the two-channel Kondo lattice where conduction electrons have spin and orbital (channel) degrees of freedom. Using the continuous-time quantum Monte?Carlo and the dynamical mean-field theory, a spontaneous breaking of the orbital symmetry is observed. The tiny breakdown of orbital occupation number, however, vanishes if the conduction electrons have the particle-hole symmetry. The proper order parameter instead is identified as a composite quantity representing the orbital-selective Kondo effect. The single-particle spectrum of the selected orbital shows insulating property, while the other orbital behaves as a Fermi liquid. This composite order is the first example of odd-frequency order other than off-diagonal order (superconductivity), and is a candidate of hidden order in f-electron systems.     

Light focusing by slot Fabry-Perot photonic crystal nanoresonator on scanning tip

We numerically investigate the propagation of light through the photonic crystal (PhC) waveguide on low refraction index material for near-field light focusing at the visible wavelength (635 nm) by incorporating a center air slot and Fabry-Perot resonator on the scanning tip. Perturbations by water and substrate refraction index changes of the PhC are analyzed by the finite-difference time-domain method to show minimal impact on light confinement and throughput. Such a total dielectric probe tip design has great potential to complement the current widely used metal-coated optical-fiber-based light confinement probe.     

Curdlan as a Polymeric Starting Material to Access C6-Modified Glucose Derivatives

We evaluated the potential of a linear β-1,3-glucan (curdlan) as a starting material to access C6-modified glucose derivatives and found that 6-bromo-6-deoxyglucose, 6-azide-6-deoxyglucose, and 6-acetamido-6-deoxyglucose could be readily prepared from curdlan through its C6-selective and quantitative modifications and subsequent acid-catalyzed hydrolysis.     

On the volume and surface area of hyperbolic polyhedra

A truncated tetrahedron is a building block of hyperbolic 3-manifolds with totally geodesic boundary. We study the relation between the volume of a truncated tetrahedron and the area of its faces which form the boundary of manifolds.     

Discrimination Between 8‐Oxo‐2′‐Deoxyguanosine and 2′‐Deoxyguanosine in DNA by the Single Nucleotide Primer Extension Reaction with Adap Triphosphate

The adenosine derivative of 2‐oxo‐1,3‐diazaphenoxazine (Adap) exhibits a superb ability to recognize and form base pairs with 8‐oxo‐2′‐deoxyguanosine (8‐oxo‐dG) in duplex DNA. In this study, the triphosphate of Adap (dAdapTP) was synthesized and tested for single nucleotide incorporation into primer strands using the Klenow Fragment. The efficiency of dAdapTP incorporation into 8‐oxo‐dG‐containing templates was more than 36‐fold higher than with dG‐containing templates, and provides better discrimination than does the incorporation of natural 2′‐deoxyadenosine triphosphate (dATP). The selective incorporation of dAdapTP into 8‐oxo‐dG templates was therefore applied to the detection of 8‐oxo‐dG in human telomeric DNA sequences extracted from H₂O₂‐treated HeLa cells. The enzymatic incorporation of dAdapTP into 8‐oxo‐dG‐containing templates may provide a novel basis for sequencing oxidative DNA damage in the genome.     

Spectrophotometric determination of titanium with o-carboxyphenylfluorone in cationic micellar media, and its equilibrium and kinetic studies

Spectrophotometric determination of titanium(IV) was accomplished with o-carboxyphenylfluorone (OCPF) in the presence of hexadecyltrimethyl ammonium chloride (HTAC) under strongly acidic media. In the determination of titanium(IV), Beer's law was obeyed in the range of 24-340 ng mL⁻¹ with an effective molar absorption coefficient (at 530 nm) and relative standard deviation of 2.24 × 10⁵ dm³ mol⁻¹ cm⁻¹ and 0.64% (n = 8), respectively. The severe interference of iron ions was easily eliminated by the addition of ethylenediaminetetraacetic acid (EDTA); the effects of other foreign substances were low. Equilibrium and kinetic studies under analytical conditions were investigated to quantitatively evaluate the reaction mechanism. The obtained orange complex is considered to be Ti(OCPF)₄. Its stability log K_f and rate constant K_obs are 16.88 and 1.65 × 10⁻² s⁻¹, respectively. It is suggested that the color of the complex is related to the species of OCPF in the solution.