Band structure and pressure-induced metallic transition in iodine – GW calculation

We have studied the band structure and the band gap closure in phase I of solid iodine under high pressure, using the methods based on the quasiparticle theory, i.e. GW approximation. Our calculations show that the band gap in the Cmca structure, which is the structure of the phase I of solid iodine, closes around 20 GPa. This pressure is near the upper boundary of phase I. We discuss the possible metallic transition in the molecular phase of solid iodine and the possible changes of the crystal structure.     

All-Fiber Optical Add-Drop Multiplexer Using a Pair of Fiber Grating Couplers

A new all-fiber optical add-drop multiplexer (ADM) using a pair of fiber grating couplers (FGCs) was proposed and first demonstrated. It was theoretically and experimentally shown that both drop and add efficiencies could be maximized in the proposed ADM. It was also clarified that the crosstalk between dropped and added signals could be improved in the proposed ADM compared with that in the single FGC. Drop and add operations in the ADM for 3-channel WDM signals with 1.6 nm wavelength spacing were confirmed. The ADM with signal amplification ability, which consists of a pair of FGCs, an EDF, and a pump-LD, was proposed and demonstrated. It was confirmed that the dropped and transmitted optical signals could be amplified in the ADM, and would be able to expand fiber routing spans.     

A Sol-Gel Synthesis for Thermally Stable Aniline/Silica Material

Aniline/silica sol-gel material was obtained. The aniline was immobilized on the silica surface using chloropropyltrimethoxysilane as bridge reagent. The base activator NaH was used to produce a fast SN₂ reaction between the base and the alkylorganosilane. The resulting modified silica was characterized by elemental analysis and infrared spectroscopy using an oven cell. The organic coverage on the surface was proportional to the organic precursor concentration. The aniline/silica materials are thermally stable up to 300°C, in high vacuum.     

A new simple route to deoxyamino sugars from non-sugar material: synthesis of d-tolyposamine and 4-epi-d-tolyposamine and formal synthesis of d-vicenisamine

A new, simple strategy has been formulated for the synthesis of deoxyamino sugars from a non-sugar starting material. Starting from the enantiomerically pure diol obtained from ethyl sorbate by Sharpless asymmetric dihydroxylation, the synthesis of two types of 2,3,4,6-tetradeoxy-4-amino sugars—d-tolyposamine and 4-epi-d-tolyposamine—, and formal synthesis of 2,4,6-trideoxy-4-amino sugar—d-vicenisamine—were performed.     

Chemical synthesis and application of C-terminally 5-carboxyfluorescein-labelled thymopentin as a fluorescent probe for thymopoietin receptor.

Thymopentin (TP5) is a synthetic pentapeptide fragment, which corresponds to position 32 - 36 of thymic polypeptide thymopoietin. Thymopoietin and TP5 display a variety of biological functions, including phenotypic differentiation of T cells and the regulation of immune systems. Previous chemical modification experiments suggested that there was an absolute requirement for N-terminal amino acids to maintain the biological activity of TP5. On the basis of this structure-activity relationship, we designed and synthesized the C-terminally 5-carboxyfluorescein-coupled TP5 (TP5-FAM) as a fluorescent probe for thymopoietin receptor. TP5-FAM could bind to the membrane of human lymphoid cell lines, MOLT-4 cells, in which the thymopoietin receptor is expressed. The binding is specific and saturable (K(d) = 33 microM). TP5 and human splenopentin are nearly equipotent inhibitors of TP5-FAM binding to the thymopoietin receptor, but porcine secretin did not show any significant inhibition of TP5-FAM binding to MOLT-4 cells. Thus, TP5-FAM is suggested to be a potent and biologically active ligand that would be useful for studying the binding and functional characteristics of the human thymopoietin receptor.     

Determination of peptide φ angles in solids by relayed anisotropy correlation NMR

A solid state NMR method is presented for determination of a backbone dihedral angle φ in peptides, being based on the previously reported method, relayed anisotropy correlation (RACO) NMR [Y. Ishii et al., Chem. Phys. Lett. 256 (1996) 133]. In the present method, the and the dipolar tensors in the system are two-dimensionally (2D) correlated via polarization transfer from to under magic angle spinning (MAS). This method was applied to N-acetyl , -valine, and the H–C–N–H dihedral angle was determined to be 154.0±1.4° or 206.0±1.4°, the former agreeing with the X-ray value of 154±5°.     

Mössbauer spectroscopic study of frozen solutions of57Co using a specially designed cryostat for time differential coincidence emission Mössbauer spectroscopy of237Np

Experiments on the⁵⁷Fe Mössbauer effect in frozen solutions were carried out in order to demonstrate the capabilities of a cryostat which was developed for the emission Mössbauer spectroscopy of²³⁷Np. We confirmed the existence of an aliovalent state of⁵⁷Fe in the temperature range from 5.5 to 35 K. However, the relative amounts of Fe(II) and Fe(III) in the frozen matrix were almost constant for the temperature range from 5.5 to 150 K. The design, operation and capabilities of the cryostat are also described.