Development of a new type multi-moderator neutron spectrometer

A multi-moderator spectrometer on which is mounted a pair of ⁶Li and ⁷Li glass scintillators has been developed as a new type neutron spectrometer which can measure the neutron spectrum in a mixed field of neutrons, charged particles and gamma-rays realized in space. The particle identification capability was investigated in neutron-gamma-ray and neutron-proton mixed fields and the neutron response functions of the spectrometer were obtained by calculations and experiments up to 200 MeV.     

A calorimetric study of the acid dissociation of the conjugate acids of poly(N-vinylimidazole) and polyallylamine

Thermodynamic parameters for acid dissociation of the conjugate acids of poly(N-vinylimidazole) and polyallylamine have been determined in the presence of sodium chloride and sodium nitrate. Even though the plots of ΔG ⁰ against the degree of dissociation, α, are highly dependent on the added salt concentration levels, the concentration effect has never been observed for the corresponding ΔH ⁰ versus α plots. The effect on the ΔG ⁰ versus α plots has been attributed to the entropy change of the counterions between a polyelectrolyte phase and a bulk solution phase. The α dependency of ΔH ⁰ is affected remarkably by the kinds of cationic polymers and counter-anions. Each ΔH ⁰ value at completely neutralized conditions is quite close to the corresponding ΔH ⁰ value of the monomer analog. The difference in the ΔH ⁰ values at fully charged conditions has been explained by the heats due to The ion-pair formation of chloride anion to the conjugate acids of poly(N-vinylimidazole) and polyallylamine has been supported by ³⁵Cl NMR measurement. It has also been suggested that chloride anions bind the basic polymer molecules even at fully neutralized conditions. Received: 2 June 1999/Accepted in revised form: 19 July 1999     

DREAM++: Flexible docking program for virtual combinatorial libraries

We present a set of programs, DREAM++ (Docking and Reaction programs using Efficient seArch Methods written in C++), for docking computationally generated ligands into macromolecular binding sites. DREAM++ is composed of three programs: ORIENT++, REACT++ and SEARCH++. The program ORIENT++ positions molecules in a binding site with the DOCK algorithm [1, 2]. Its output can be used as input to REACT++ and SEARCH++. The program REACT++ performs user-specified chemical reactions on a docked molecule, so that reaction products can be evaluated for three dimensional complementarity with the macromolecular site. The program SEARCH++ performs an efficient conformation search on the reaction products using a hybrid backtrack [3, 4] and incremental construction [5, 6] algorithm. We have applied the programs to HIV protease–inhibitor complexes as test systems. We found that we can differentiate high-affinity ligands based on several measures: interaction energies, occupancy of protein subsites and the number of successfully docked conformations for each product. Encouraged by the results in the test case, we applied the programs to propose novel inhibitors of HIV protease. These inhibitors can be generated by organic reactions using commercially available reagents. They are alternatives to the inhibitors synthesized by Glaxo [7, 8].     

Intense THz-radiation from semiconductors under magnetic field irradiated with femtosecond laser pulses

The THz-radiation power from InAs reaches sub-mW level in a 1.7-T magnetic field irradiated with femtosecond laser pulses of 1.5-W average power. The THz-radiation power is related almost quadratically both to the magnetic field and to the excitation laser power. Furthermore, the THz-radiation spectrum is found to be controlled by the excitation pulsewidth, chirp direction of the excitation pulse, and the magnetic field.     

Convenient synthesis of 1,6,7,8-substituted 2-(3′,4′-substituted-phenyl)-4-quinolones via a 4-ethoxyflavylium salt

Condensation of 2-hydroxyacetophenone with benzaldehyde in the presence of 70% perchloric acid in ethyl orthoformate gave the corresponding 4-ethoxyflavylium perchlorate, which was treated with aqueous ammonia or methylamine solution to afford 1,6,7,8-substituted 2-(3′,4′-substituted-phenyl)-4-quinolone in fair to good yield.     

Biphasic electrochemical peptide synthesis

The large amount of waste derived from coupling reagents is a serious drawback of peptide synthesis from a green chemistry viewpoint. To overcome this issue, we report an electrochemical peptide synthesis in a biphasic system. Anodic oxidation of triphenylphosphine (Ph₃P) generates a phosphine radical cation, which serves as the coupling reagent to activate carboxylic acids, and produces triphenylphosphine oxide (Ph₃P O) as a stoichiometric byproduct. In combination with a soluble tag-assisted liquid-phase peptide synthesis, the selective recovery of desired peptides and Ph₃P O was achieved. Given that methods to reduce Ph₃P O to Ph₃P have been reported, Ph₃P O could be a recyclable byproduct unlike byproducts from typical coupling reagents. Moreover, a commercial peptide active pharmaceutical ingredient (API), leuprorelin, was successfully synthesized without the use of traditional coupling reagents.

The large amount of waste derived from coupling reagents is a serious drawback of peptide synthesis from a green chemistry viewpoint.     

Polymacromonomers with polyolefin branches synthesized by free-radical homopolymerization of polyolefin macromonomer with a methacryloyl end group

Polymacromonomers with polyolefin branches were successfully synthesized by free-radical homopolymerization of polyolefin macromonomer with a methacryloyl end group. Propylene-ethylene random copolymer (PER) with a vinylidene end group was prepared by polymerization using a metallocene catalyst. Then, the unsaturated end group was converted to a hydroxy end group via hydroalumination and oxidation. The PER with the hydroxy end group was easily reacted with methacryloyl chloride to produce methacryloyl-terminated PER (PER macromonomer; PERM). The free-radical polymerization of thus-obtained PERM was done using 2,2′-azobis(isobutyronitorile) (AIBN) as a free-radical initiator. From NMR analyses, the obtained polymers were identified as poly(PERM). Based on gel permeation chromatography (GPC), the estimated degree of polymerization (D_p) of these polymers were about 30. Thus, new class of polymacromonomers with polyolefin branches was synthesized.     

New methodology for synthesizing polyolefinic graft block copolymers and their morphological features

This paper describes a new synthetic route for polyolefinic graft block copolymers by adopting coupling reaction between terminally hydroxylated polyolefins and maleic anhydride grafted polyolefins. Terminally hydroxylated polypropylene (PP-OH) was coupled with maleic anhydride modified polyethylene (PE-g-MAH) and such ethylene-propylene random copolymer (EPR-g-MAH) to give polyolefinic graft block copolymers (PE-g-PP and EPR-g-PP, respectively). The formation of PE-g-PP was confirmed by enhancement on molecular weight and it brought about distinctive decrease in size of dispersed domain in its phase separation morphology. Occurrence of coupling reaction to give EPR-g-PP was indicated by extreme decrease in its solubility to n-decane and it led to unique morphology demonstrating lamella microstructure that had never been reported for a comparable polyolefin composite.     

Development of a new density functional program for all-electron calculation of proteins

In this article, we propose a new molecular orbital program for all-electron calculation of proteins which is based on density functional theory. To carry it out in a fully analytical way, we adopted the (pure-) analytical Xα method and modified it for saving a lot of memories for large-scale calculations. The recent software technology sophisticated in information science is inevitably applied to achieve calculations of large molecular systems. The program is coded by the object-oriented language C + +, its output is shown graphically, and the most of the procedures in this program are controlled through an efficient graphical user interface developed by ourselves. Such technology supports the safe construction of the huge software, the tidy representation of enormous data, and the ready control of complex calculations. Test calculations with various sizes of glycine polypeptides indicate that the computation time is proportional to the 1.7 powers of the number of residues. This result suggests that the all-electron calculations of proteins consisting of over 1000 atoms could be performed with distributed and/or massively parallel computers. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 245–256, 1997