Laser-induced fluorescence of cyclohexadienyl (c-C6H7) radical in the gas phase

A laser-induced fluorescence spectrum was observed in the 500-560 nm region when a mixture of 1,4-cyclohexadiene and oxalyl chloride was photolyzed at 193 nm. The observed excitation spectrum was assigned to the A (2)A(2)<--X (2)B(1) transition of the cyclohexadienyl radical c-C6H7, produced by abstraction of a hydrogen atom from 1,4-cyclohexadiene by Cl atoms. The origin of the A<--X transition of c-C(6)H(7) was at 18 207 cm(-1). From measurements of the dispersed fluorescence spectra and ab initio calculations, the frequencies of several vibrational modes in both the ground and excited states of c-C(6)H(7) were determined: nu(5)(C-H in-plane bend)=1571, nu(8)(C-H in-plane bend)=1174, nu(10)(C-C-C in-plane bend)=981, nu(12)(C-C-C in-plane bend)=559, nu(16)(C-C-C out-of-plane bend)=375, and nu(33)(C-C-C in-plane bend)=600 cm(-1) for the ground state and nu(8)=1118, nu(10)=967, nu(12)=502, nu(16)=172, and nu(33)=536 cm(-1) for the excited states.     

Determination of trace elements and radioactive materials by substoichiometric isotope dilution analysis

Substoichiometric isotope dilution analysis has been applied for the determination of trace elements in liquid samples, of carrier content in radioisotope solution and of concentration of organic reagent. Cu in mineral acids and in ZnSe single crystal was determined by the substoichiometric extraction with dithizone. The values of 1.8 and 0.018 ppm in nitric acid and distilled one and of 1.4 and 0.44 ppm in ZnSe were obtained. Cu and P carrier contents in⁶⁴Cu and³²P solutions were determined by the substoichiometric extractions with dithizone in CCl₄ and with molybdic acid into MIBK in the series of the solutions adding various amounts of Cu or P carrier. An analogous method has been applied for the determination of dithizone and diethyldithiocarbamate solutions. The method was also applied for the determination of⁶⁰Co radioactivity in environmental samples. The analytical result of water samples is described.     

A self-assembling protein template for constrained synthesis and patterning of nanoparticle arrays

Self-assembling biomolecules that form highly ordered structures have attracted interest as potential alternatives to conventional lithographic processes for patterning materials. Here, we introduce a general technique for patterning nanoparticle arrays using two-dimensional crystals of genetically modified hollow protein structures called chaperonins. Constrained chemical synthesis of transition metal nanoparticles is initiated using templates functionalized with polyhistidine sequences. These nanoparticles are ordered into arrays because the template-driven synthesis is constrained by the nanoscale structure of the crystallized protein. We anticipate that this system may be used to pattern different classes of nanoparticles based on the growing library of sequences shown to specifically bind or direct the growth of materials.     

Solvent extraction of permanganates (Na, K) by 18-crown-6 ether from water into 1,2-dichloroethane: elucidation of an extraction equilibrium based on component equilibria

Ion-pair formation constants (K_MLA mol⁻¹ dm³) of Na⁺– and K⁺–18-crown-6 ether (18C6) complexes with MnO₄⁻ in water (w) were determined potentiometrically at 25 °C. Simultaneously, extraction constants (K_ex mol⁻² dm⁶) of the permanganates with 18C6 from w into 1,2-dichloroethane at 25 °C were obtained from the spectrophotometric determination of distribution ratios of the permanganates. These K_ex values were divided into K_MLA and other three component equilibrium constants and thereby extraction-selectivity and -ability were discussed in comparison with corresponding metal picrate–18C6 extraction systems reported before.     

Determination of radioactive nuclides of uranium and thorium series and estimation of α-flux in LSI constituent materials

Gamma-rays of nuclides of uranium and thorium series in silicone resin and ceramics were measured with a Ge(Li) detector. The state of radioactive equilibrium was determined by comparing the concentrations of uranium and thorium with the radioactive concentrations of²¹⁴Pb and²¹²Pb. The radioactive equilibrium was attained in silicone resin but not in ceramics. The -flux was calculated from the concentrations of uranium and thorium and their daughter nuclides. The calculated values of -flux agreed with that of -flux measured.     

Rate constant of the reaction of NO3 with CH2I2 measured with use of cavity ring-down spectroscopy

We have applied cavity ring-down spectroscopy to a kinetic study of the reaction of NO₃ with CH₂I₂ in 25–100 Torr of N₂ diluent at 298 K. The rate constant of reaction of NO₃ + CH₂I₂ is determined to be (4.0 ± 1.2) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ in 100 Torr of N₂ diluent at 298 K. The rate constant increases with increasing pressure of buffer gas below 100 Torr. The reaction of CH₂I₂ with NO₃ has the potential importance at nighttime in the atmosphere.     

Aryl-aryl coupling reaction using a novel and highly active palladium reagent prepared from Pd(OAc)2, 1,3-bis[diphenylphosphino]propane (DPPP), and Bu3P

A palladium-assisted coupling reaction of aryl triflate with arene was investigated, and a novel Pd reagent prepared from equimolar Pd(OAc)2, 1,3-Bis[diphenylphosphino]propane (DPPP), and Bu3P was developed. This method is useful for intramolecular biaryl coupling reactions, not only between aryl triflate and arene (triflate-amide), but also between aryl halide and arene (halo-amide).     

De novo design, synthesis, and function of semiartificial myoglobin conjugated with coiled-coil two-alpha-helix peptides

The introduction of a flavin chromophore on the myoglobin (Mb) surface and an effective electron-transfer (ET) reaction through the flavin were successfully achieved by utilizing the self-assembly of heterostranded coiled-coil peptides. We have prepared a semiartificial Mb, named Mb-1alphaK, in which an amphiphilic and cationic alpha-helix peptide is conjugated at the heme propionate (Heme-1alphaK). Heme-1alphaK has a covalently bound iron-protoporphyrin IX (heme) at the N terminus of a 1alphaK peptide sequence. This sequence was designed to form a heterostranded coiled-coil in the presence of a counterpart amphiphilic and anionic 1alphaE peptide sequence in a parallel orientation. Two peptides, Fla(1)-1alphaE and Fla(31)-1alphaE, both incorporating a 10-methylisoalloxazine moiety as an artificial flavin molecule, were also prepared (Fla=2-[7-(10-methyl)isoalloxazinyl]-2-oxoethyl). Heme-1alphaK was successfully inserted into apomyoglobin to give Mb-1alphaK. Mb-1alphaK recognized the flavin-modified peptides and a two-alpha-helix structure was formed. In addition, an efficient ET from reduced nicotinamide adenine dinucleotide to the heme center through the flavin unit was observed. The ET rate was faster in the presence of Fla(1)-1alphaE than in the presence of Fla(31)-1alphaE or the equivalent molecule that has no peptide chain. These results demonstrate that the introduction of a functional chromophore on the Mb surface can be achieved by using specific peptide-peptide interactions. Moreover, the dependence of the ET rate on the position of the flavin indicated that the distance between the heme active site and the flavin chromophore was regulated by the three-dimensional structure of the designed polypeptide.     

Polycyclic N-heterocyclic compounds. XLI. Synthesis of 4-substituted 6,7-dihydro-5H-pyrimido[5,4-d][1]benzazepines, 1,2,5,6-tetrahydro-4H-imidazo[1′,2′:1,6]pyrimido[5,4-d][1]benzazepines and their related compounds as a series of potential blood platelet aggregation inhibitors

As a series of polyheterocyclic compounds for exploitation as anti-platelet agents, tricyclic heterocyclic compounds, 4-substituted 6,7-dihydro-5H-pyrimido[5,4-d][1]benzazepines 3–6, 9, 12–14 , and 16–26 , having nitrogen, oxygen, or sulfur containing functional groups at the 4-position, were prepared. In addition, tetra-cyclic heterocyclic compounds, 3-methyl-1,2,5,6-tetrahydro-4H-imidazo[1′,2′:1,6]pyrimido[5,4-d][1]benzaze-pinium chloride ( 7 ), 1,2,5,6-tetrahydro-4H-imidazo[1′,2′:1,6]pyrimido[5,4-d][1]benzazepines 10a-e , 2,3,6,7-tetrahydro-1H 5H-pyrimido[1′,2′:1,6]pyrimido[5,4-d][1]benzazepine ( 11 ), and 1,2,5,6-tetrahydro-4H-thiazolo-[3′,2′:1,6]pyrimido[5,4-d][1]benzazepinium chloride ( 15 ) via ring closure of 4-(hydroxyalkylamino)- 6, 9a-e , and 3c , and 4-(2-hydroxyethylthio)-6,7-dihydro-5H-pyrimido[5,4-d][1]benzazepine ( 14 ) with phosphoryl chloride or thionyl chloride, respectively, were also prepared. Their inhibitory activities against collagen-induced aggregation of rabbit blood platelets in vitro were investigated. Among them, compound 5 having a morpholino group at the 4-position on the tricyclic nucleus, which enhanced the activity more than 14-fold as compared with aspirin, was found to have the most satisfactory in inhibitory activity.     

Substoichiometric precipitation of fluoride with lanthanum

The substoichiometric precipitation of fluoride with lanthanum was studied by using¹⁸F and¹⁴⁰La tracers and it was found that fluoride could be precipitated substoichiometrically with lanthanum and the reaction ratio between fluoride and lanthanum was 3∶1. The pH range at which fluoride can be separated substoichiometrically with lanthanum is between 2 and 8. Barium and indium interfere in the precipitation of fluoride, sodium, copper and manganese, however, not. Fluorosilicate can also be precipitated substoichiometrically by using lanthanum as a precipitant and the reaction ratio between fluorosilicate and lanthanum was 1∶2. This separation was applied for the determination of oxygen in silicon crystals. The concentration of oxygen measured in some silicon crystals was between 5 and 27 ppm and in good agreement with those by non-destructive method and infrared spectrophotometry.