Radiological status of Rongelap Island in 1999

A radiological survey and whole body counting of ¹³⁷Cs were carried out in Rongelap Island (main island) of Rongelap Atoll in July 1999. The maximum values of ¹³⁷Cs contamination and of g-ray dose rate were 39 kBq/m² and 0.033 mSv/h, respectively. The maximum a and b gross counting rates on the surface of ground were 1 cpm and 182 cpm in active area of 72 cm², respectively. Activity of ^239,240Pu for soil was 80 Bq/kg in the top 5 cm and aerial deposition was 3.4 kBq/m² in Rongelap Island in 1999. The body burden of ¹³⁷Cs was observed to be 27±11 Bq/kg for 6 workers. Assessment of external and internal annual doses (0.1 and 0.07 mSv/y) indicates that as of 1999 there is no large risk to the inhabitants of Rongelap Island from a radiological point of view. The radiological status of Rongelap Island, which was severely contaminated by the radiological fallouts of nuclear testings carried out in 1954, has improved year by year as shown by the decrease of ¹³⁷Cs. The effective halftime of ¹³⁷Cs, which is estimated to be 6.6 y is much shorter than the physical half-life of ¹³⁷Cs. Radioactive contamination in Kaballe Island, (a part of the northern islands used for farming) which is located 25 km northeast of Rongelap Island, was still high in 1999. One site nearby a beach was highly contaminated with ¹³⁷Cs, where the maximum activity of ¹³⁷Cs was 3.4 MBq/m², a-ray of 2 cpm, b-ray of 1205 cpm and g-ray of 0.73 mSv/h. Activity of ^239,240Pu in soil (n = 1) was 294 Bq/kg (top 5 cm) and 16 kBq/m².     

Structural difference between a superconducting sodium cobalt oxide and its related phase

Monolayer hydrate (MLH) Na_xCoO₂·y′H₂O was obtained from superconducting bilayer hydrate (BLH) Na_xCoO₂·yH₂O by partial extraction of H₂O molecules between the CoO₂ layers. Magnetization measurements indicated that electron densities in the CoO₂ layer of the MLH phase remained unchanged after the water extraction. Nevertheless, superconductivity was completely suppressed in the MLH phase. This strongly suggests that the highly 2D nature in the BLH phase due to its thick insulating layers consisting of H₂O molecules and Na⁺ ions plays an important role for inducing superconductivity.     

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.     

Living cationic ring-opening polymerization by water-stable initiator: synthesis of a well-defined optically active polythiourethane

Living cationic ring-opening polymerization under air and water was achieved using a well-defined water-resistant cationic initiator in dichloromethane without purification at ambient temperature.     

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.     

High-resolution submicron patterning of self-assembled monolayers using a molecular fluorine laser at 157 nm

Using a molecular fluorine laser at 157 nm wavelength, submicron patterning of organosilane self-assembled monolayers (SAMs) is demonstrated utilizing mask-contact photolithography. An organosilane, namely, octadecyltrimethoxysilane [ODS, CH(3)(CH(2))(17)Si(OCH(3))(3)], SAM is chemisorbed onto Si substrates covered with a 2 nm thick oxide layer and subsequently patterned using the laser. The optical path of the laser beam and the photomask-sample space are evacuated and then backfilled and purged with nitrogen during laser firing. The resulting pattern is investigated using various measurement techniques. The scanning probe microscopy images show that patterns are transferred to the SAM-covered Si substrates and that 500 nm features are successfully photoprinted in this way.     

Chlorovulones,new halogenated marine prostanoids with an antitumor activity from the stolonifer clavularia viridis Quoy and Gaimard

New halogenated marine prostanoids, chlorovulone I, II and III were isolated from the stolonifer $\text{Clavularia}$$\text{viridis}$ Quoy and Gaimard. The structure elucidation and the antitumor activity of chlorovulones were described.     

Electronic structures of exohedral lanthanide-C60 clusters

We have studied the electronic structures of several gas phase exohedral lanthanide (Ln)-C(60) clusters, Ln(n)C(60) (Ln=Pr, Ho, Tb, Tm, Eu, and Yb) with n=1-4, by photoionization spectroscopy of the neutrals and photoelectron spectroscopy of their anions. Both of the spectroscopic analyses reveal that most of the Ln atoms preferably take +3 oxidation states, while Eu atoms alone assume +2 oxidation states, and that C(60) accepts up to twelve donated electrons in Ln(n)C(60). An additional photoionization examination of the oxygen atom mixing into the Ln(n)C(60) clusters demonstrated that each oxygen atom reduces two electrons from C(60). This result implies that the number of accepted electrons in C(60) can be varied by a suitable choice of the number of Ln atoms and O atoms.     

Methane Decomposition in a Barium Titanate Packed-Bed Nonthermal Plasma Reactor

The behavior of lattice oxygen species of the ferroelectric material during methane oxidation was investigated using a nonthermal plasma reactor packed with BaTiO ₃ pellets. Lattice oxygen species in BaTiO ₃ play an important role in the formation of N ₂ O and the oxidation of CH ₄ . The oxidation products such as CO and CO ₂ were formed from independent reaction pathways. Lattice oxygen species were able to preferentially oxidize the carbon species deposited on the pellet surface into CO. Also, N ₂ O and NO _x were independently formed in the N ₂–O ₂ reaction, suggesting that different oxygen species give N ₂ O and NO _x. N ₂ O was produced by the oxidation of molecular nitrogen with lattice oxygen species.     

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.