Signals for scalar top quark atep collider HERA

In the framework of the minimal supersymmetric standard model (MSSM) and theR-parity breaking model (RBM), we investigate production processes of the scalar top (stop) at HERA energies. These models are characterized by the possible existence of the light stop whose mass is lighter than those of the top quark and the other squarks. It is shown that in the MSSM the stop pair production via boson-gluon fusion gives a sizeable cross section and the most serious background $ep \to ec\bar cX$ could be suppressed by appropriate kinematical cuts. We also show that in the RBM the stop is singly produced in the neutral current processes and we have a clear signal as a sharp peak in the Bjorken parameterx distribution of the scattered electron.     

Ageladine A: an antiangiogenic matrixmetalloproteinase inhibitor from the marine sponge Agelas nakamurai

A novel MMP inhibitor, ageladine A (1) with antiangiogenic activity was isolated from a marine sponge Agelas nakamurai. Structure 1 was determined by a combination of spectroscopic and chemical methods to be an unprecedented structure of 4-(4,5-dibromo-1H-pyrrol-2-yl)]-1H-imidazo[4,5-c]pyridin-2-amine.     

Direct catalytic asymmetric Michael reaction of hydroxyketones: asymmetric Zn catalysis with a Et2Zn/linked-BINOL complex

Full details of our direct Michael addition of unmodified ketones using new asymmetric zinc catalysis are described. Et(2)Zn/(S,S)-linked-BINOL complexes were successfully applied to direct 1,4-addition reactions of hydroxyketones. The first generation Et(2)Zn/(S,S)-linked-BINOL 1 = 2/1 system was effective for 1,4-addition of 2-hydroxy-2'-methoxyacetophenone (3). Using 1 mol % of (S,S)-linked-BINOL 1 and 2 mol % of Et(2)Zn, we found that a 1,4-addition reaction of beta-unsubstituted enone proceeded smoothly at 4 degrees C to afford products in high yield (up to 90%) and enantiomeric excess (up to 95%). In the case of beta-substituted enones, however, the first generation Et(2)Zn/(S,S)-linked-BINOL 1 = 2/1 system was not at all effective. The second generation Et(2)Zn/(S,S)-linked-BINOL 1 = 4/1 with MS 3A system was developed and was effective for various beta-substituted enones to afford products in good dr, yield (up to 99%), and high enantiomeric excess (up to 99% ee). With the Et(2)Zn/1 = 4/1 systems, catalyst loading for beta-unsubstituted enone was reduced to as little as 0.01 mol % (substrate/chiral ligand = 10 000). The new system was also effective for 1,4-addition reactions of 2-hydroxy-2'-methoxypropiophenone (9) to afford chiral tert-alcohol in high enantiomeric excess (up to 96% ee). Mechanistic investigations as well as transformations of the Michael adducts into synthetically versatile intermediates are also described.     

Novel bromotyrosine derivatives that inhibit growth of the fish pathogenic bacterium Aeromonas hydrophila, from a marine sponge Hexadella sp

Three new bromotyrosine derivatives, 11-N-methylmoloka'iamine (1), 11-N-cyano-11-N-methylmoloka'iamine (2), and kuchinoenamine (3), were isolated as antibacterial constituents from a marine sponge Hexadella sp. Their structures were elucidated on the basis of spectral and chemical methods. They exhibited moderate antibacterial activity against the fish pathogenic bacterium Aeromonas hydrophila.     

Photophysical properties of oligo(2,3-thienyleneethynylene)s

Photophysical properties of oligo(2,3-thienyleneethynylene)s (nTE, n denotes the number of thiophene rings, n = 2, 3) in benzene were investigated using steady-state, time-resolved fluorescence, and transient absorption spectroscopies. For 2TE, generation of the radiative S2 and nonradiative S1 states was confirmed. Upon excitation, the S2 state was initially generated and deactivated to the S1 state within 10 ps. The S1 state exhibited the transient absorption band at 470 nm, of which the lifetime was estimated to be 5.3 ns. In the case of 3TE, on the other hand, it was revealed that the radiative S1 state with a transient absorption peak at 650 nm was generated upon excitation. The T1 states of nTE were generated from the S1 states. The quantum yields were estimated to be 0.52 and 0.54 for 2TE and 3TE, respectively. Extremely fast reactions in the higher triplet excited state were indicated for both 2TE and 3TE.     

Direct observation of the one-electron reduction of methyl viologen mediated by the CO2 radical anion during TiO2 photocatalytic reactions

The one-electron reduction of methyl viologen (MV(2+)) mediated by the carbon dioxide radical anion (CO(2)(*-)) during photocatalytic reactions in a colloidal TiO(2) aqueous solution (pH 2) has been investigated by time-resolved absorption spectroscopy. The formation of MV(*+) generated from the one-electron reduction reaction with CO(2)(*-), which is generated from the one-electron oxidation reactions with the photogenerated holes (h(+)), was directly observed. The spectral features of the photogenerated charge carriers and the kinetic analysis of the formation process of MV(*+) revealed that the CO(2)(*-), desorbed from the surface, reacts with MV(2+) via a homogeneous electron-transfer process in the bulk solution.     

Calculation of membrane potential in synaptosomes with use of a lipophilic cation (tetraphenylphosphonium)

To estimate membrane potential in synaptosomes with the use of tetraphenylphosphonium (TPP+), an equation relating the amount of TPP+ accumulated in synaptosomes with membrane potential was derived from the following two assumptions. (1) TPP+ molecules were distributed into plasma membranes, mitochondria and cytosol of synaptosomes. (2) TPP+ achieves a Nernst equilibrium across both the synaptosomal and inner mitochondrial membranes. We propose three methods for calculation of membrane potential using this equation. The concentration of TPP+ was measured under various controlled conditions with an electrode selective for TPP+. The amount of TPP+ accumulated in synaptosomes was determined by measuring the difference between its initial concentration and the concentration after addition of synaptosomes, and membrane potential was estimated by the three methods. The resting potential of synaptosomes was estimated to be -75 to -90 mV by all of these methods. Membrane potentials under various controlled conditions were calculated, and the characteristics of the methods for estimation of membrane potential and those of membrane potential obtained by the methods are discussed.     

Kinetics of transient end-to-end contact of single-stranded DNAs

The formation of the pyrene (Py) dimer radical cation (Py(2)(*+)) was used to measure the kinetics of the intrastrand end-to-end contact rates of single-stranded DNAs (ssDNAs) in the 10 nanoseconds to the tens of microseconds time range. ssDNAs labeled with Py at both ends with the lengths of 3, 6, and 9 mer were synthesized, and the two-photon ionization method was employed to generate a Py(*+), which enables the measurements of the end-to-end contact rates from 10 ns. The formation rate of Py(2)(*+) depended on the length and the sequence of the ssDNAs, and about 1 order of magnitude faster rates were observed for the T-rich ssDNAs compared to those for the corresponding length of A-rich ssDNAs, showing that ssDNA made from adenines is much more rigid than that composed of thymidines. As for the T-rich ssDNAs, the formation of Py(2)(*+) attributed to the misfolded structures was also observed, which is consistent with the configurational diffusion model suggested by Ansari and co-workers.     

Bioactive marine metabolites VI. Structure elucidation of discodermin a,an antimicrobial peptide from the marine sponge Discodermia kiiensis

The structure of an antimicrobial peptide discodermin A isolated from the marine sponge Discodermia kiiensis has been elucidated as CHO-d-Ala-l-Phe-d-Pro-d-t-Leu-l-t-Leu-d-Trp-l-Arg-d-Cys(O₃H)-l-T$\text{hr-}\text{l}\text{-MeGln-}\text{d}\text{-Leu-}\text{l}\text{-Asn-}\text{l}\text{-Thr-Sar}$.     

New resveratrol oligomers in the stem bark of Vatica pauciflora

Five new resveratrol oligomers; pauciflorols A-C (1-3), isovaticanols B (6) and C (8), and three new oligostilbene glucosides; pauciflorosides A (11), B (13), C (14), were isolated from the stem bark of Vatica pauciflora (Dipterocarpaceae) together with known 17 resveratrol oligomers (4, 5, 7, 9, 10, 12 and 15-25) and bergenin (26). The structures of isolates were established on the basis of detailed spectroscopic analysis. The typical and characteristic spectral properties of some resveratrol oligomers were also discussed.