Development of rapid bioassay method for plutonium

For the internal dosimetry of plutonium, a urine bioassay method is very useful but requires several days to obtain the result of the analysis. To shorten the time required for the urine bioassay, a rapid method for plutonium analysis using the ICP-MS system was developed. In this chemical procedure, a microwave oven was applied for sample digestion, and an extraction chromatography resin was used for the separation of plutonium. The measurement time was extremely reduced by application of the ICP-MS as compared to alpha-spectrometry. The total analysis time was about 12 hours and the detection limit was 0.3 mBq/sample. The short analysis time and the low detection limit indicate that this method is useful not only for special monitoring but also for routine monitoring.     

Enzymatic formation of pyrrole-containing novel cyclic polyprenoids by bacterial squalene:hopene cyclase

A convergent synthesis provided two pyrrole-containing squalene analogues, in which a C₂₀ isoprene unit is connected to pyrrole, 2-(geranylgeranyl)pyrrole and 2-(farnesyldimethylallyl)pyrrole. When incubated with recombinant squalene:hopene cyclase from Alicyclobacillus acidocaldarius, 2-(farnesyldimethylallyl)pyrrole was enzymatically converted to a 10:1 mixture of a tricyclic and a bicyclic unnatural novel polyprenoids, whereas 2-(geranylgeranyl)pyrrole was not a substrate for the enzyme.     

Photochemical reaction between tryptophan and thymine

Irradiation of tryptophan and thymine in aqueous solution produced two photoadducts whose structures were determined by spectral data and X-ray crystallographic analysis.     

Bond-selective photodissociation of partially deuterated ammonia molecules: photodissociations of vibrationally excited NHD(2) in the 5nu(NH) state and NH(2)D in the 5nu(ND) state

Ultraviolet photodissociation of NHD(2) excited to the fourth overtone state of the NH stretching mode (5nu(NH)) and NH(2)D excited to that of the ND stretching mode (5nu(ND)) has been investigated by using a crossed laser and molecular beams method. Branching ratio between the NH and ND bond dissociations has been determined by utilizing a (2+1) resonance enhanced multiphoton ionization scheme of H and D atoms. For the photolysis of NHD(2) in the 5nu(NH) state, the NH dissociation cross section is 5.1+/-1.4 times as large as the ND dissociation cross section per bond. On the other hand, for the photolysis of NH(2)D in the 5nu(ND) state, the ratio of the NH dissociation cross section per bond to the ND dissociation cross section decreases to 0.68+/-0.16. In comparison with the branching ratios for the photolysis of vibrationally unexcited NH(2)D and NHD(2), the present results indicate that the excitation of the NH stretching mode enhances the NH dissociation with ca. two times larger NH/ND branching ratio, whereas the excitation of the ND stretching mode results in the preferential ND dissociation with ca. 3-4 times larger ND/NH branching ratio than that for the vibrational ground states. The mechanism of the bond-selective enhancement has been discussed in terms of the energetics and dynamics of wave packet.     

Biologically active constituents of Magnolia salicifolia: inhibitors of induced histamine release from rat mast cells.

The extracts of the flower buds of Magnolia salicifolia showed remarkable anti-allergy effects in passive cutaneous anaphylaxis (PCA) test. The bioactive constituents of this medicinal drug were isolated by monitoring their activities with an in vitro bioassay system measuring inhibitory effects on induced histamine release from rat mast cells. Of the ten isolated compounds magnosalicin is a new compound of neolignan structure. In addition to the isolated compounds samples of coumarins and lignans were evaluated their biological activities with the in vitro bioassay.     

Architecture and solution properties of amphiphilic polymer brushes with peripheral charged ions

Functionalized poly(ethylene oxide) (PEO) macromonomers (alpha -tertiary amino and omega -methacryloyl groups) were prepared by ring-opening polymerization of live PEO anions end-capped with styrene oxide using 2-[2-(N ,N -dimethylamino)-ethoxy]ethanol potassium alkoxides as an initiator with methacryloyl chloride. PEO brushes were synthesized by free-radical homopolymerization of such PEO macromonomers. These brushes were converted into peripherally charged brushes by quaternization. We studied the solution properties of both types of brushes from the viewpoint of charge effect. It was found from dynamic light scattering (DLS) that the polymer brushes formed a single macromolecule in solution due to crowding of side chains. It was speculated from angular dependence measurements that the polymer brushes with large aspect ratios took a geometrical anisotropic conformation such as a cylinder. In methanol with a low dielectric constant, radius of gyration (R(G)), and cross-sectional radius of gyration (R(G,C)) of the polymer brushes with charged side chains were smaller than those of the polymer brushes without charges. In a solvent with a low dielectric constant such as methanol, ionic groups do not dissociate and condense. On the other hand, these physical values in an aqueous solution were somewhat larger than those of the polymer brushes without charges. In water with a high dielectric constant, peripherally charged brushes were strongly stabilized by electric double layers.