Reaction mechanism for target-like products from197Au target bombarded with12C ions of energies above 100 MeV/u

Target-like products, that is,^191–200Au,^185–200Pt, and^183–195Ir, from¹⁹⁷Au target bombarded with¹²C ions at the energies of 180, 230, and 400 MeV/u were measured by using off-line gamma-ray spectrometry combined with chemical separation procedures. Spallation systematics by Rudstam reproduces well the measured cross sections for formation of platinum and iridium isotopes. It was found that the cross sections of gold nuclides increase with increase of the incident energy in the range studied and they are enhanced if compared with the reported proton-induced reaction of gold at a similar incident energy. It is suggested that the electromagnetic dissociation process plays a role for production of such gold nuclides.     

A versatile scaffold for facile synthesis of fluorescent cyano-substituted stilbenes

Here we report the facile derivatization of a cyano-substituted stilbene into higher π-extended analogues. The cyano-substituted stilbene, which serves as a synthetic scaffold, has a bromo group and a formyl group on its 4- and 4′-position of the phenylene rings and thus readily undergoes selective transformation into other functional groups using various simple organic reactions. The resultant π-conjugated molecules that contain a cyano-substituted stilbene skeleton exhibit fluorescence in solution and in the solid state.     

Direct counting of submicrometer-sized photosynthetic apparatus dispersed in medium at cryogenic temperature by confocal laser fluorescence microscopy: estimation of the number of bacteriochlorophyll c in single light-harvesting antenna complexes chlorosomes of green photosynthetic bacteria

The number of pigments in single light-harvesting complexes (chlorosomes) were calculated by imaging single chlorosomes in a frozen buffer at cryogenic temperature with a confocal laser fluorescence microscope and pigment extraction. Chlorosomes were isolated from two types of green photosynthetic bacteria Chlorobium (Chl.) tepidum and Chloroflexus (Cfl.) aurantiacus and were individually imaged in the frozen medium. Each fluorescence spot observed mainly came from a single chlorosome and was ascribable to self-aggregates of bacteriochlorophyll (BChl) c molecules as core parts of chlorosomes. A three-dimensional distribution of fluorescence of single chlorosomes was analyzed, and the number of chlorosomes in a volume of 54,000 microm(3) was counted directly. On the basis of the results, averaged numbers of the BChl c molecules contained in a single chlorosome of Chl. tepidum and Cfl. aurantiacus were determined to be 1.4 x 10(5) and 9.6 x 10(4), respectively. The present numbers are almost comparable to those estimated by other methods (Martinez-Planells et al., Photosynth. Res. 2002, 71, 83 and Monta?o et al., Biophys. J. 2003, 85, 2560).     

Synthesis and properties of thermoplastic propyl-etherified amylose

Amylose was etherified with 1-bromopropane in DMSO. The degree of substitution (DS) was varied by altering the feed ratio of 1-bromopropane. The structures of the products were characterized by IR and 1H-NMR spectroscopy. When the molar feed ratio of 1-bromopropane to hydroxyl groups of amylose was beyond 7.5, the hydroxyl groups were completely substituted with propyl ether groups. The etherified amylose with DS 1.9 showed a glass transition temperature (T_g), and that with DS 2.3 or 3.0 showed both T_g and melting temperature (T_m) (DS 3.0 means complete substitution). The etherification imparted melt processability and solubility in nonpolar organic solvent to amylose.     

Formation of Supramolecular Nanostructures through in Situ Self-Assembly and Post-Assembly Modification of a Biocatalytically Constructed Dipeptide Hydrazide**

Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.     

A Defective Nanotube Molecule of C552H496N24 with Pyridinic and Pyrrolic Nitrogen Atoms

A 3-nm molecule comprising a cylindrical core and cross-shaped rims was designed and synthesized by developing a modular synthetic route. By using a cyclic precursor from previous studies as a starting material, multiple carbazole units were installed at the rims of the defective cylinder. The defective cylinder was synthetically doped with two types of nitrogen atoms, that is, pyridinic and pyrrolic nitrogen atoms, which resulted in solvatochromic shifts in fluorescence by charge-transfer interactions. The structure of the large, C₅₅₂H₄₉₆N₂₄ molecule was fully disclosed by crystallographic analyses, and the unique helical arrangement of nitrogen-doped cylinders in the crystal was revealed.     

Catalytic Pauson-Khand-type reaction using aldehydes as a CO source

[reaction: see text]. Rhodium complex-catalyzed carbonylative alkene-alkyne coupling proceeds using aldehydes as a CO source. Cinnamaldehyde is the best CO donor, and various cyclopentenones were provided in high isolated yields by a solvent-free system.     

Dithienylethenes with a novel photochromic performance

Dithienylethenes with low decoloration quantum yields and thermal reversibility at high temperature above 100 degrees C were prepared. Introduction of bulky alkoxy substituents at 2- and 2'-positions of the thiophene rings strongly suppressed the cycloreversion quantum yields. The quantum yields were lower than 10(-3), and the photogenerated color remained stable enough under room light. On the other hand, the bulky alkoxy substituent decreased the thermal stability of the colored closed-ring isomers at high temperature. The color of the dithienylethene with cyclohexyloxy substituents faded out in less than 1 min at 160 degrees C.