Plutonium isotopes in the surface air in Japan: Effect of Chernobyl accident

Plutonium isotope concentrations in the surface air at Tsukuba, Japan are reported during the period from 1981 to the end of 1986. The^239,240Pu concentration in the surface air, which showed a marked seasonal variation with a spring maximum and fall minimum, decreased until the end of 1985 according to the stratospheric residence time of 1.15 years. In May 1986, elevated^239,240Pu concentrations with high²³⁸Pu/^239,240Pu activity ratios were observed. The serial trend of plutonium concentration in the surface air is similar to the concentrations of the Chernobyl-released radionuclides. These findings suggest that a significant part of the plutonium in the surface air in May 1986 was due to the Chernobyl fallout. The size distribution of plutonium bearing particles indicates that plutonium isotopes were mechanically released in the Chernobyl accident. The surface air concentration of plutonium from the Chernobyl accident was much lower than the concentrations of the volatile fission products, and increased the monthly mean^239,240Pu concentration by only 0.03 Bqm^–3.     

Combined analysis of microwave and infrared spectra of methyl iodide: rotational and l-type doubling constants of the v5, v3+v6 and v2 states

The rotational constant B and the l-type doubling constant q were determined for the v₅, v₃+v₆ and v₂, states of CH₂I from the microwave transition frequencies, in combination with the infrared data previously reported. Since these vibrational states were coupled through the Fermi resonance and the xy-type E-E and A₁-E Coriolis resonances, the analysis was made by setting up and solving the complete form of the secular determinants of the energy matrices. The rotational and l-type doubling constants were determined as B₅, = 0.250 173 cm^?1, B₃₆ = 0.247 600 cm^?1, B₂ = 0.249 369 cm^?1, q₅ = ?0.000 027 cm^?1 and q₃₆ = ?0.000 179 cm^?1, which are unperturbed by Fermi and Coriolis interactions. Other band constants for v₅ and v₃+v₆ were also refined in accordance with the new values of B₅ and B₃₆. The present study indicated that the combined analysis of microwave and infrared spectral data was useful for the precise determination of vibration-rotation, levels in the perturbed system.     

Effect of the mobility of ligands in polyrotaxanes on order structure of water clusters

The effect of the mobility of ligands (maltose groups) in the polyrotaxanes (pRXs) on the structure of the surrounding water molecules was investigated. Raman spectra of collective OH stretching vibration of water molecules in aqueous solutions of maltose-pRX conjugates with different alpha-cyclodextrin (alpha-CD) threading on a poly(ethylene glycol) (PEG) chain was measured. The mobility of maltose groups was estimated by measuring the relaxation time T2 of the C1 protons in maltose groups bound on alpha-CD by NMR experiment. A positive correlation between the Raman intensity of the collective band and the relaxation time T2 was obtained. This result indicates that the degree of order of the water clusters is higher as the mobility of maltose groups increases in these conjugate solutions. It is suggested that rapid motion of maltose groups in the pRX conjugate can contribute to preserving ordered structure of the bulk water clusters.     

Reverse zymography using fluorogenic substrates for protease inhibitor detection

A novel, sensitive method for detecting protease inhibitors by using fluorescent protease substrates in gels is described. The protease inhibitors were separated on sodium dodecyl sulfate (SDS)-polyacrylamide gels containing a copolymerized peptide substrate, namely 4-methyl-coumaryl-7-amide (MCA). As the incorporated substrates in the gel, Boc-Phe Ser-Arg-MCA was used for trypsin, Suc-Ala-Ala-Pro-Phe-MCA for alpha-chymotrypsin, and Z-Phe-Arg-MCA for papain. After electrophoresis, washing and incubating the gel with the target protease solutions allowed the substrate to be cleaved by the protease, and the release of the fluorescent 7 amino-4 methyl-coumarin (AMC), which was detected under a UV transilluminator. The uncleaved peptide-MCA substrate remained where the inhibitors were present, and was visualized as dark blue bands on the light-green fluorescent background gel. This new method offers several advantages over other previous methods including: (i) greatly increased sensitivity can be achieved in a shorter period of time, which may be useful for discovering new protease inhibitors in small amounts of crude material; (ii) the procedure is quite simple and quick since the incubation period is very short and no time is needed for staining and destaining steps; (iii) since these probes using substrate specificity/target proteases, they are excellent tools for detection and discrimination of unknown protease inhibitors for various target proteases.     

m-Diethynylbenzene macrocycles: syntheses and self-association behavior in solution

m-Diethynylbenzene macrocycles (DBMs), buta-1,3-diyne-bridged [4(n)]metacyclophanes, have been synthesized and their self-association behaviors in solution were investigated. Cyclic tetramers, hexamers, and octamers of DBMs having exo-annular octyl, hexadecyl, and 3,6,9-trioxadecyl ester groups were prepared by intermolecular oxidative coupling of dimer units or intramolecular cyclization of the corresponding open-chain oligomers. The aggregation properties were investigated by two methods, the (1)H NMR spectra and the vapor pressure osmometry (VPO). Although some discrepancies were observed between the association constants obtained from the two methods, the qualitative view was consistent with each other. The analysis of self-aggregation by VPO revealed unique aggregation behavior of DBMs in acetone and toluene, which was not elucidated by the NMR method. Namely, the association constants for infinite association are several times larger than the dimerization constant, suggesting that the aggregation is enhanced by the formation of dimers (a nucleation mechanism). In polar solvents, DBMs aggregate more strongly than in chloroform due to the solvophobic interactions between the macrocyclic framework and the solvents. Moreover, DBMs self-associate in aromatic solvents such as toluene and o-xylene more readily than in chloroform. In particular, the hexameric DBM having a large macrocyclic cavity exhibits extremely large association constants in aromatic solvents. By comparing the aggregation properties of DBMs with the corresponding acyclic oligomers, the effect of the macrocyclic structure on the aggregation propensity was clarified. Finally, it turned out that DBMs tend to aggregate more readily than the corresponding phenylacetylene macrocycles, acetylene-bridged [2(n)]metacyclophanes, owing to the withdrawal of the electron density from the aromatic rings by the butadiyne linkages which facilitates pi-pi stacking interactions.     

Quantitative study of diffuse increased 99mTc-methylene diphosphonate accumulation of both kidneys

Patients with diffuse increased accumulation in both kidneys on 99mTc-MDP bone scintigram were evaluated quantitatively. Among 1,100 cases, 7 (0.63%) showed this finding. The accumulation density ratios of kidneys/lumbal vertebra in A/D exchanged images of these patients were compared with control group, so that these ratios of patient group were higher than control group statistically. In conclusion, the accumulation density ratio was made the index of diffuse increase accumulation in both kidneys on 99mTc-MDP bone scintigram.     

Chiral recognition in NMR spectroscopy using crown ethers and their ytterbium(III) complexes

Chiral crown ethers 1 and 5 are useful enantiomeric discriminating agents in ¹H NMR spectroscopy for neutral and protonated primary amines, amino acids, and amino alcohols. The presence of the carboxylic acid groups in 1 and 5 provide sites at which ytterbium(III) can bind. Adding ytterbium(III) nitrate to crown–substrate mixtures in methanol-d₄ causes shifts in the spectra of substrates and often enhances the chiral discrimination in the ¹H NMR spectrum. The enhancement in enantiomeric discrimination that occurs in the presence of ytterbium(III) allows lower concentrations of the crown ether to be used in chiral recognition studies. Several amide derivatives of 1 were prepared and evaluated as chiral NMR discriminating agents, although except for 1e, these were less effective than 1.     

Geochemical studies on the Chernobyl radioactivity in environmental samples

Artificial radionuclides in deposition and airborne dust samples in 1986 were measured at Tsukuba and 11 stations in Japan. In May 1986, the Chernobyl radioactivity was observed in rain and air samples in Japan. The Chernobyl-derived Pu isotopes, which are characterized by higher²³⁸Pu/^239,240Pu (85) and²⁴¹Pu/²³⁸Pu (0.5) activity ratios than those of the nuclear test-derived Pu and⁹⁰Sr, were detected in deposition and airborne dust samples in Japan, as well as volatile radionuclides such as¹³¹I and¹³⁷Cs. However, the activities of Pu isotopes and⁹⁰Sr observed in Japan were about two and three orders of magnitude lower than those expected from the activity ratios in the total release at Chernobyl, which means that the residence time of Pu in the air was shorter than that of¹³⁷Cs. In order to understand the fractionation between the Chernobyl radionuclides we studied about individual wet and dry deposition. The results suggest that this cause is due to the difference of the particle size of radionuclide-bearing particles, which may be related to the release process of Chernobyl radionuclides.     

Effect of omega-hydrogenation on the adsorption of fluorononanols at the hexane/water interface: pressure effect on the adsorption of fluorononanols

The interfacial tension gamma of the hexane solution of 1H,1H-perfluorononanol (FDFC(9)OH) and its omega-hydrogenated analogue, 1H,1H,9H-perfluorononanol (HDFC(9)OH), against water was measured as a function of pressure and concentration at 298.15 K in order to clarify the effect of omega-dipole on the orientation of fluorononanol molecules from the viewpoint of volume. The adsorbed films of both alcohols exhibit two kinds of phase transitions among three different states: the gaseous, expanded, and condensed states. The partial molar volume changes of adsorption - in the expanded and condensed states were evaluated and compared between the two systems. The - values of both alcohols are negative, and thus the alcohol molecules have smaller volume in the adsorbed film than in the bulk solution. Furthermore, the value was obtained through the evaluation of by the density measurement of the bulk hexane solution. It was found that the value of HDFC(9)OH is smaller than that of FDFC(9)OH in the condensed state. On the basis of three matters concerning the molecular structure of alcohols, the occupied area at the interface, and the orientation of FDFC(9)OH in the adsorbed film deduced from the earlier results of X-ray reflectivity measurement, the mean tilt angle of HDFC(9)OH from the interface normal in the condensed film was estimated to be 15 degrees . The thermodynamic estimation demonstrated here is highly valuable one to provide structure information on an adsorbed film.     

(+)-Phorboxazole A synthetic studies. A highly convergent, second generation total synthesis of (+)-phorboxazole A

[structure: see text] A second generation total synthesis of the potent antitumor agent (+)-phorboxazole A (1) has been achieved. The cornerstone of this approach comprises a more convergent strategy, involving late-stage Stille union of a fully elaborated C(1-28) macrocycle with a C(29-46) side chain. The second generation synthesis entails the longest linear sequence of 24 steps, with an overall yield of 4.2%.