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Distance dependence of the electric field effect on the interlayer photoinduced electron tunneling from cyanine dye to viologen through a fatty acid has been examined using various spacer layers of fatty acid, based on the fluorescence measurements. The magnitude of the field-induced change in tunneling rate is shown to increase monotonically with decreasing the donor−acceptor distance.

Silicon- and carbon-bridged phenylnitroxides were synthesized. They exhibited similar ESR profiles independent of the nature of the sp³ bridge and the substitution mode of the phenylene units. The spectra revealed a quintet signal at room temperature, which became a broad triplet by lowering the temperature. Accumulated ESR measurements at 77 K led to the successful observation of a signal at Δms = 2, indicating that the triplet state was involved in this system.

Dithienosiloles (DTSs) bearing conjugated aryl substituents on the thiophene rings (1 and 2) were prepared and their optical, electrochemical, and electron-transporting properties were investigated in comparison with those of simple DTSs having no conjugated substituents on the thiophene rings (4−6). UV absorption bands of 1 and 2 are red shifted from those of 4−6 by 40−80 nm, reflecting the expanded π-conjugation, whereas the first oxidation peaks in the cyclic voltammograms of 1 and 2 appear at potentials a little lower or almost the same energies relative to those of 4−6, depending on the nature of the substituents. The electron-transporting properties of 1 and 2 were evaluated by the performance of electroluminescent (EL) devices having vapor-deposited DTS, Alq, and TPD layers, as the electron-transport, emitter, and hole-transport, respectively. The results indicated that introduction of aryl substituents to DTSs led to inferior performance of the devices in most cases, while the device with 1c bearing trimethylsilylpyridyl substituents exhibited high efficiency of current−luminance energy conversion and emitted a green light with a maximum luminance of 16 000 cd/m². A trap-controlled electron transporting model is proposed to explain their performance.

Electric field effects on photoinduced electron-transfer processes have been examined in a polymer film for methylene-linked compounds of phenanthrene and N,N-dimethylaniline, based on the measurements of the field effects on fluorescence spectra. Both intra- and intermolecular electron-transfer processes are enhanced by an electric field (F), depending on the methylene chain length, and LE fluorescence emitted from the locally excited state of phenanthrene chromophore is quenched by F. Exciplex fluorescence is also influenced by F. The magnitude of the change in molecular polarizability following fluorescence process has been determined from the Stark shift both for LE fluorescence and for exciplex fluorescence.

The first total synthesis of (±)-linderol A, a hexahydrodibenzofuran isolated from Lindera umbellata bark, with potent inhibitory activity on melanin biosynthesis of cultured B-16 melanoma cells was achieved via a 20-step of reaction in 7.64% overall yield starting from 4,6-dimethoxysalicylaldehyde.

This paper reports on the organization, expression, and function of the divergently transcribedflbGandflaNoperons in the hook gene cluster ofCaulobacter crescentus. The transcription initiation site offlbGwas determined previously, and in this work the transcription map was completed by locating the 3′ end of the mRNA using nuclease S1 protection assays. A previous genetic study had suggested that theflbGoperon is comprised of four genes; however, the nucleotide sequence revealed three tandemly arranged ORFs that correspond to 5′-flbG,flbH, andflgE. FlbG is similar to FliK proteins which are required for termination of hook synthesis, FlbH is similar to FlgD proteins which are essential scaffolding proteins that cap the hook during its assembly, and FlgE corresponds to the hook structural protein. The divergently transcribedflaNgene codes for a hook associated protein I homolog based on its inferred amino acid sequence similarity to FlgK proteins. Based on the amino acid sequence similarities and phenotypes of mutants,flbG,flbH, andflaNhave been renamedfliK,flgD, andflgK. FlgD, FlgE, and FlgK proteins, with apparent molecular masses of 23, 68, and 41 kDa, respectively, were expressed from plasmids in a cell-free coupled transcription-translation system, and a protein corresponding to FliK was identified as part of a 190-kDa FliK-LacZ fusion protein. We present evidence showing that, in addition to its role in termination of hook synthesis, FliK is also required for initiation of hook assembly.

UV irradiation (266 nm) from a nanosecond and/or a femtosecond laser-induced reconstruction of CO adsorbed layer on Pt(111) electrode. The current peak shape in the cyclic voltammogram (CV) for the electrochemical oxidation of the adsorbed CO was varied by the irradiation, which did not leave any change in the CV response on the adsorption free Pt(111) surface. Although the current peak shape in the CV was changed, the total charge for the CO oxidation remained constant. The green light irradiation (532 nm) from the lasers did not induce any change in the CV. These findings suggested that the UV induced CO desorption and re-trapping cycles were sustained on the electrode surface, which passed through electronic excited states at the surface.

Susceptibility to Plasmodium chabaudi depends on the relative dominance of T_h1/T_h2 responses in host mice. A T_h2-dominant response during the early phase of infection in susceptible A/J mice causes a fatal disease course due to severe malaria. Schistosoma mansoni is a potent inducer of a T_h2-dominant response not only to the parasite antigens, but also to other antigens concurrently existing in the host animals. In spite of S. mansoni infection, these A/J mice escape death from malaria and showed accompanied enhanced production of IFN-γ to malaria antigens. Treatment with anti-IFN-γ mAb in S. mansoni-infected A/J mice abolished the resistance to malaria, indicating that IFN-γ was responsible for the resistance to P. chabaudi in S. mansoni-infected A/J mice. Results in this study show that under certain circumstances, S. mansoni infection can promote type 1 immune responses in A/J mice that normally develop T_h2 responses.

Background: CD80 (B7-1) and CD86 (B7-2) play an important role in antigen presentation to effector cells. Recent studies have demonstrated that these costimulatory molecules are also expressed on activated T cells. However, the functional role of CD80 and CD86 expressed on allergen-specific T cells in atopic diseases has not yet been clarified. Objective: We sought to determine the functional role of CD80 and CD86 expressed on allergen-specific T cells in atopic diseases. Methods: We assayed the expression of CD80 and CD86 on allergen-specific T-cell lines from patients with perennial allergic rhinitis stimulated by Dermatophagoides farinae -crude (Der f-c) antigen, 1 of the major allergens causing house dust mite allergy. T-cell proliferation induced by Der f-c-specific T-T cell interactions was measured, and the role of CD80 and CD86 in this proliferation was examined. In addition, we compared the proportion of CD45RO ^+ CD86 ^+ T cells in primary culture of PBMCs stimulated by Der f-c antigen between patients with perennial allergic rhinitis and control subjects. Results: On T-cell activation, CD86 antigen was upregulated earlier than CD80. Both CD80 and CD86 expressed on Der f-c-specific T cells could provide costimulatory signals to induce allergen-specific T-cell proliferation that was partially inhibitable by both anti-CD80 and anti-CD86 mAbs. The proportion of CD45RO ^+ CD86 ^+ T cells in primary culture from atopic patients was significantly higher than that from control subjects. Conclusion: These results suggest that costimulatory molecules, such as CD80 and CD86, expressed on allergen-specific T cells may be involved in the amplification of allergen-specific immune responses through T-T cell interactions in atopic diseases. (J Allergy Clin Immunol 1999;104:222-7.)

Electroabsorption spectra of meso,meso-linked zinc porphyrin arrays doped in a PMMA polymer film have been measured with a field modulation spectroscopy, and the change in electric dipole moment (Δμ) and in molecular polarizability has been evaluated for the transition into each of the exciton splitting components of the Soret band. Δμ following photoexcitation is non-zero in the oligomers, and the magnitude becomes larger with the increasing number of linked molecules, suggesting that photoinduced charge transfer occurs along the linked porphyrin array.

Surface morphology of oxacyanine dye (OC) suddenly changes in mixed Langmuir−Blodgett films composed of OC, arachidic acid, and methyl arachidate when the OC fraction becomes more than 30 mol %. The agglomerates of OC show a ring structure just like a rubber band. The diameter and the shape of the “rubber band” change with different OC fractions, and microcrystalline domains appear when J-type aggregates are formed. The morphological change of the surface monolayer is well-correlated with a change in the electroabsorption spectra of the OC chromophore.

Exciplex fluorescence in a mixture of N-ethylcarbazole (ECZ) and dimethyl terephthalate (DMTP) doped in a PMMA polymer film, which appears as a result of photoinduced electron transfer from ECZ to DMTP, is quenched by an electric field as the concentration of the electron donor, i.e., ECZ, is increased. Even when the DMTP concentration is increased, the exciplex fluorescence is not quenched by an external electric field as long as the ECZ concentration is low. These concentration dependences indicate that a hole transport occurs very efficiently and that an electron transport does not occur in this photoinduced electron-transfer system. In fact, a photocurrent could be detected in a mixture of ECZ and DMTP in PMMA films only when the concentration of ECZ was high.

Summary: A new method for the determination of the mobile phase volume (V m) in liquid chromatography is presented based on the model regarding the retention of ionic solutes in the presence of eluent electrolytes. TheV m value can be determined by measuring the retention volumes of two ions that have the same charge in two eluent electrolyte systems. Compared with the methods using isotopically labelled eluent components or inorganic salts asV m markers, the method presented is proved to give more reasonableV m values for both normal and reversed-phase liquid chromatography. As well as in binary mixed solvent systems, theV m values in single solvent systems can be determined by this method.

Summary: Gel chromatographic behaviour of tris(1, 10-phenanthroline)iron(II), tris(2,2′-bipyridine)iron(II) and tris(glycinato)cobalt(III) on Sephadex G-10 or G-25 was investigated by TLC with 0.001–1.0M NaCl as the eluent. The zone shapes and RM values of tris(1,10-phenanthroline)iron(II) and tris(2,2′-bipyridine)iron(II) were appreciably dependent on the sample and eluent concentration, while the neutral complex, tris(glycinato) cobalt(III), exhibited the round zones with constant RM values. The order of RM values was found to be tris(glycinato)cobalt(III