Improved measurement of the K+-->pi+nunu; branching ratio

An additional event near the upper kinematic limit for K+-->pi(+)nunu; has been observed by experiment E949 at Brookhaven National Laboratory. Combining previously reported and new data, the branching ratio is B(K+-->pi(+)nunu;)=(1.47(+1.30)(-0.89))x10(-10) based on three events observed in the pion momentum region 211相似文献   

Construction of the multidecker anthracene-silver(I) system by intramolecular pi-pi interactions

As a continuation of the study on the construction of the multidecker aromatic compounds with pi-pi interactions, the anthracene derivatives 9,10-dimethylanthracene (dman), 9,10-diphenylanthracene (dpan), and 7,12-dimethylbenz[a]anthracene (dmban) have been studied toward complexation with the silver(I) ion. The crystal structures of [Ag(dman)(0.5)(p-xylene)(ClO(4))], [Ag(2)(dpan)(0.5)(C(6)H(6))(0.5)(CF(3)SO(3))(2)], and [Ag(2)(dmban)(2)(ClO(4))(2)](p-xylene), together with the metal-free ligand dpan, have been determined by single-crystal X-ray diffraction. These pi-electron-rich aromatic compounds are found to have great promise as an approach to the effective self-assembly of high nuclearity in a multilayer fashion.     

Syntheses and structures of photochromic silver(I) coordination polymers with cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene

Five novel silver(I) coordination polymers with cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3- thienyl)ethene (cis-dbe) were synthesized and are characterized in this paper. Treatment of AgCF(3)SO(3) or AgCF(3)CO(2) with cis-dbe afforded [Ag(2)(cis-dbe)(CF(3)SO(3))(2)] (1) and [Ag(2)(cis-dbe)(CF(3)CO(2))(2)] (2), and both complexes exhibit a 1-D infinite chain structure with two cyano groups and two thienyl groups of the ligand bridging four metal ions. Reaction of AgC(n)()F(2)(n)(+1)CO(2) with cis-dbe gave rise to an unprecedented cocrystallization of a 2-D sheet structure, [Ag(2)(cis-dbe)(C(n)F(2)(n)(+1)CO(2))(2)], where n = 2 (3), 3 (4), and 4 (5). Upon irradiation with 450 nm light, these five silver(I) complexes turned orange or red from yellow, and the color reverted to yellow on exposure to 560 nm light, indicative of the reversible cyclization/ring-opening reaction occurring in the crystalline phase. Furthermore, different anions gave not only the different structural dimensions but also the different photoresponsive patterns. The correlation between the crystal structures and the photochromic reactivity is discussed.     

Activities of the bimodal fluorescent protein produced by Photobacterium phosphoreum strain bmFP in the luciferase reaction in vitro

The activity of the bimodal fluorescent protein (bmFP) (lambda max, 488 and 517 nm) in the in vitro luciferase reaction has been studied. The bmFP that is produced by Photobacterium phosphoreum strain bmFP is a dimer of two homologous subunits binding four riboflavin 5'-phosphate (FMN)-myristate chromophores. The addition of bmFP to the luciferase reaction in the presence of the lumazine protein prevented the lumazine protein-induced blue shift in the emission band. The bmFP reduced electrochemically serves as a substrate in the luciferase reaction in the absence of added FMN, resulting in light emission with a single maximum at about 487 nm. The bmFP was also active in lieu of FMN in the NADH/FMN oxidoreductase (flavin reductase)-luciferase coupled bioluminescence reaction in the absence of added FMN. In the coupled reaction, bioluminescence with the isolated bmFP chromophore was weaker than that with the holo-bmFP. After bmFP was used in luciferase reactions initiated either chemically or electrochemically, it was still capable of emitting bimodal fluorescence.     

LOCALIZATION OF MONO-L-ASPARTYL CHLORIN e6 (NPe6) IN MOUSE TISSUES

Abstract It is known that HpD is retained longer by malignant tissue than normal tissue and is therefore a useful material for photodynamic therapy (PDT). Currently, vigorous research is being conducted throughout the world to discover a new material which can have greater cancer cell affinity than hematoporphyrin derivative (HpD) and will be used effectively for PDT. Investigation has been conducted to determine the spectral characteristics and cancer cell affinity of NPe6, a recently developed material.
Structurally, a double bond on the D-ring of the porphyrin ring of mono-L-aspartyl chlorin e6 (NPe6) has been reduced, thereby changing its spectral properties from that of HpD. This difference accounts for the stronger absorption bands in wavelengths longer than those of HpD. Furthermore, NPe6 in tumor showed stronger absorption at 660 nm than HpD. Absorption by hemoglobin (Hb) in the blood occurs at wavelengths in the range 500-600 nm, thereby lowering light transmittance. A compound which has a strong absorption band at wavelengths longer than 600 nm and consequently is not affected by Hb will naturally be activated by light at a greater depth in tissue than compounds which do not share this characteristic. The localization of NPe6 in sarcoma and various internal organs was examined with an endoscopic spectrophotometer using an excimer dye laser. After 72 h i.v. NPe6 injection, the results indicate that NPe6 has 10 times greater uptake in malignant tissue cells than in normal organs. Based on the above observations, it was concluded that NPe6 could be effective for PDT if toxicity is low and that this compound has a high malignant tissue affinity.     

Effects of molecular structure on the stability of a thermotropic liquid crystal. Gas electron diffraction study of the molecular structure of phenyl benzoate.

As a model of the core of molecules forming liquid crystals, the molecular structure of phenyl benzoate (Ph-C(=O)-O-Ph) at 409 K was determined by gas electron diffraction, and the relationship between the gas-phase structures of model compounds and the nematic-to-liquid transition temperatures was studied. Structural constraints were obtained from RHF/6-31G ab initio calculations. Vibrational mean amplitudes and shrinkage corrections were calculated from the harmonic force constants given by normal coordinate analysis. Thermal vibrations were treated as small-amplitude motions, except for the phenyl torsion, which was treated as a large-amplitude motion. The potential function for torsion was assumed to be V(phi(1),phi(2)) = V(12)(1 - cos 2phi(1))/2 + V(14)(1 - cos 4phi(1))/2 + V(22)(1 - cos 2phi(2))/2, where phi(1) and phi(2) denote the torsional angles around the C-Ph and O-Ph bonds, respectively. The potential constants (V(ij)()/kcal mol(-)(1)) and the principal structure parameters (r(g)/A, angle(alpha)/deg) with the estimated limits of error (3sigma) are as follows: V(12) = -1.3 (assumed); V(14) = -0.5(9); V(22) = 3.5(15); r(C=O) = 1.208(4); r(C(=O)-O) = 1.362(6); r(C(=O)-O) - r(O-C) = -0.044 (assumed); r(C(=O)-C) = 1.478(10); = 1.396(1); angleOCO = 124.2(13); angleO=CC = 127.3(12); angleCOC = 121.4(22); ( angleOCC(cis) - angleOCC(trans))/2 = 3.0(15); ( angleC(=O)CC(cis) - angleC(=O)CC(trans))/2 = 4.8(17), where < > means an average value and C-C(cis) and C-C(trans) bonds are cis and trans to the C(=O)-O bond, respectively. The torsional angle around the O-Ph bond was determined to be 64(+26,-12) degrees. An apparent correlation was found between the contributions of the cores to the clearing point of liquid crystals and the gas-phase structures of model compounds of the cores of mesogens, i.e., phenyl benzoate, trans-azobenzene (t-AB), N-benzylideneaniline, N-benzylideneaniline N-oxide (NBANO), trans-azoxybenzene (t-AXB), and trans-stilbene. The structures of t-AB, NBANO, and t-AXB have been obtained by our research group.     

Spiral, herringbone, and triple-decker silver(I) complexes of benzopyrene derivatives assembled through eta(2)-coordination

Three novel silver(I) complexes with benzopyrene derivatives were synthesized and characterized in this paper. Treatment of AgClO(4)*H(2)O with 7-methylbenzo[a]pyrene (L(1)) afforded [Ag(2)(L(1))(toluene)(0.5)(ClO(4))(2)](n)() (1) which exhibits a 2-D sheet structure with double-stranded helical motifs. Reaction of AgCF(3)SO(3) with dibenzo[b,def ]chrysene (L(2)) gave rise to an unprecedented cocrystallization structure, ([Ag(2)(L(2))(CF(3)SO(3))(2)][Ag(2)(toluene)(2)(CF(3)SO(3))(2)])(n)() (2), formed by a 2-D neutral lamellar polymer and a 1-D neutral rodlike one. The ligand benzo[e]pyrene (L(3)) coordinated to silver(I) ions generating a closed triple-decker tetranuclear complex [Ag(4)(L(3))(4)(p-xylene)(ClO(4))(4)] (3) which can be regarded as a stacking polymer owing to existing intermolecular pi-pi stack interactions. The structural diversity of the silver(I) coordination polymers with polycyclic aromatic hydrocarbons is not only related to the stacking patterns of free polycyclic aromatic hydrocarbons in the crystalline state, but also the geometric shapes of the molecules for these free ligands. In addition, the coordination of solvents to metal ions plays a crucial role in the formation of the unprecedented coordination polymeric architectures. The ESR spectroscopic results, conductivity, and synthesis properties are also discussed.     

Vinyl polymerization. 422. Initiation mechanism of uncatalyzed polymerization by polyethyleneglycol

The initiation mechanism on the radical polymerization of vinyl monomers by polyethyleneglycol (PEG-300) in aqueous solution was studied. The initiating radical species were determined by means of the spin trapping technique. They were concluded to be generated by the hydrogen atom transfer from the monomer adsorbed at the ether group of PEG-300 to the free monomer.