The antiapoptotic effect of low-dose UVB irradiation in NIH3T3 cells involves caspase inhibitions

UVB irradiation is a well-known apoptosis induction factor. However, we have previously found that low doses of UVB irradiation inhibited apoptosis induced by both serum starvation and lack of extracellular matrix, involving a significant inhibition of caspase-3/7 activation. In this study, we report on the relationship between the UVB-induced anti-apoptotic effect and caspase-3/7 inhibition by reactive oxygen species (ROS). The UVB-induced antiapoptotic effect was partially prevented by an antioxidant agent, N-acetylcysteine. A ROS-generating agent, menadione and a pro-oxidant agent, H2O2 also showed an effect that was similar to the UVB-induced antiapoptotic effect, indicating that ROS contributed to the antiapoptotic effect. UVB irradiation significantly suppressed caspase-3/7 activation, which was caused by the inhibition of proteolysis and not by the inhibition of enzymatic activity itself. The prevention of proteolysis was also confirmed by both the following results: one is the inhibition of in vitro caspase-3/7 and -9 activation in cell lysates exposed to UVB in the presence of cytochrome c and dATP, which was caused by the production of ROS, and the other is the inhibition of in vitro caspase-3/7 activation in the presence of active caspase-9. These results showed that the inhibition of the caspase cascade downstream mitochondria by ROS production, leading to a significant inhibition of caspase-3/7 activation, was one of the causes of the antiapoptotic effect by small doses of UVB irradiation.     

Nonylphenol Polyethoxylates Degraded by Three Different Wavelengths of UV and Their Genotoxic Change—Detected by Generation of γ‐H2AX

UV rays in sunlight are an important factor in the degradation of chemicals. In this study, we investigated the degradation of nonionic surfactants, nonylphenol polyethoxylates (NPEOs) with 10 or 70 ethylene oxide (EO) units using UVA, B and C, and their genotoxic change based on phosphorylation of histone H2AX (γ‐H2AX), a marker of DNA damage. NPEOs were degraded dependent on the energy of UV, that is, UVC having the highest energy was most effective, whereas UVA having the lowest energy caused little change. The EO side chain of NPEO(70) was broken near the benzene ring by UV, producing NPEOs with a shortened EO chain (around 10 units). The generation of γ‐H2AX reflected the pattern of degradation; shortening of the EO chain changed NPEO(70) into an inducer for γ‐H2AX, and degradation of NPEO(10) attenuated the genotoxicity. The γ‐H2AX generated by NPEO(10) and UV‐degraded NPEO(70) was independent of the cell cycle. The formation of DNA double strand breaks detected by gel electrophoresis was consistent with the results for γ‐H2AX. These results suggested that UV rays can make NPEOs harmless or genotoxic according to the degradation of the EO side chain, the effects being dependent on wavelength.     

Electric conductivities of 1:1 electrolytes in liquid methanol along the liquid-vapor coexistence curve up to the critical temperature. I. NaCl, KCl, and CsCl solutions

The molar conductivities Lambda of NaCl, KCl, and CsCl in liquid methanol were measured in the concentration range of (0.3-2.0) x 10(-3) mol dm(-3) and the temperature range of 60-240 degrees C along the liquid-vapor coexistence curve. The temperature range corresponds to the solvent density range of (2.78-1.55)rhoc, where rhoc = 0.2756 g cm(-3) is the critical density of methanol. The concentration dependence of Lambda at each temperature and density (pressure) has been analyzed by the Fuoss-Chen-Justice equation to obtain the limiting molar conductivity Lambda0 and the molar association constant KA. For all the electrolytes studied, Lambda0 increased almost linearly with decreasing density at densities above 2.0rhoc, while the opposite tendency was observed at lower densities. The relative contribution of the nonhydrodynamic effect on the translational friction coefficient zeta was estimated in terms of Deltazeta/zeta, where the residual friction coefficient Deltazeta is the difference between zeta and the Stokes friction coefficient zetaS. At densities above 2.0rhoc, Deltazeta/zeta increased with decreasing density though zeta and Deltazeta decrease, and the tendencies are common for all the ions studied. The density dependences of zeta and Deltazeta/zeta were explained well by the Hubbard-Onsager (HO) dielectric friction theory based on the sphere-in-continuum model. At densities below 2.0rhoc, however, the experimental results cannot be explained by the HO theory.     

Atomically Precise Alloy Nanoclusters

Metal nanoclusters (NCs) have a particle size of about one nanometer, which makes them the smallest unit that can give a function to a substance. In addition, metal NCs possess physical and chemical properties that are different from those of the corresponding bulk metals. Metal NCs with such characteristics are expected to be important for use in nanotechnology. Research on the precise synthesis of metal NCs and elucidation of their physical/chemical properties and functions is being actively conducted. When metal NCs are alloyed, it is possible to obtain further various electronic and geometrical structures and functions. Thus, research on alloy NCs has become a hot topic in the study of metal NCs and the number of publications on alloy NCs has increased explosively in recent years. Such publications have provided much insight into the effects of alloying on the electronic structure and function of metal NCs. However, the rapid increase in knowledge has made it difficult for researchers (especially those new to the field) to grasp all of it. Therefore, in this review, we summarize the reported chemical composition, geometrical structure, electronic structure, and physical and chemical properties of Au_n−xM_x(SR)_m, Ag_n−xM_x(SR)_m, Au_n−xM_x(PR₃)_l(SR)_m, and Ag_n−xM_x(PR₃)_l(SR)_m (Au=gold, Ag=silver, M=heteroatom, PR₃=phosphine, and SR=thiolate) NCs. This review is expected to help researchers understand the characteristics of alloy NCs and lead to clear design guidelines to develop new alloy NCs with intended functions.     

Molecular recognition in a supramolecular hydrogel to afford a semi-wet sensor chip

This communication describes a new molecular recognition chip using a semi-wet microenvironment provided by a self-assembled hydrogel. On the basis of the evidence that the molecular recognition capability of artificial chemosensors are practically retained even in the hydrogel compared to those in aqueous solution, we miniaturized the functionalized hydrogel to produce an unprecedented molecular recognition chip. We believe that the present noncovalent immobilization method is generally applicable to many chemosensors, which leads to a unique semi-wet sensor chip suitable to convenient and high-throughput assay to plural analytes.     

Rhodium(I)/Chiral Diene‐Catalyzed Enantioselective Addition of Boronic Acids to N‐Unsubstituted Isatin‐Derived Ketimines

Enantioselective addition of boronic acids to N‐unsubstituted isatin‐derived ketimines was realized using rhodium(I)/chiral diene catalysts. The reactions can be performed in the presence of catalytic amounts of a base to give adducts in high yield with high enantioselectivity. Preliminary mechanistic information including a computational model to explain the observed enantioselectivity is also provided.     

Catalytic Activity of Hexokinase in Reversed Micelles

Reversed micelles can control the size of water pools and the physical property of water by changing W(0)(=[water]/[surfactant]). Hexokinase (HK) activity seems to be easily affected by the microenvironment in the neighborhood of the enzyme because it is assumed that HK binds to the outer mitochondrial membrane by insertion of its hydrophobic NH(2) tail. The catalytic activity of HK was examined in reversed micelles in order to study the effect of the microenvironment in the neighborhood of HK on the activity. Sodium bis(2-ethylhexyl)sulfosuccinate (AOT), hexadecyltrimethyl ammonium chloride (HTAC), and octaoxyethylene dodecyl ether (C(12)E(8)) were used as anionic, cationic, and nonionic surfactants, respectively. HK activity was obtained by measuring ATP and ADP amounts with HPLC. The high electrostatic inner surfaces of AOT and HTAC reversed micelles were not favorable for HK to exhibit the catalytic activity, but the activity in HTAC reversed micelles was 2-3 times higher than that in AOT reversed micelles and the activities in both reversed micelles revealed an optimum at W(0)=10. The phenomenon was discussed in connection with the location of HK, nonuniform distribution of substrates, and the size and physical properties of the water pools. On the other hand, HK activity was much higher in C(12)E(8) reversed micelles than in AOT and HTAC reversed micelles and increased with the concentration of C(12)E(8). This suggests that HK activity is easily revealed in hydrated ethylene oxide chains. In conclusion, it was demonstrated that HK activity depends on the microenvironment such as the electrostatic field, the physical properties of water, and the hydrophobicity. Copyright 2001 Academic Press.     

Cooperation between artificial receptors and supramolecular hydrogels for sensing and discriminating phosphate derivatives

This study has successfully demonstrated that the cooperative action of artificial receptors with semi-wet supramolecular hydrogels may produce a unique and efficient molecular recognition device not only for the simple sensing of phosphate derivatives, but also for discriminating among phosphate derivatives. We directly observed by confocal laser scanning microscopy that fluorescent artificial receptors can dynamically change the location between the aqueous cavity and the hydrophobic fibers upon guest-binding under semi-wet conditions provided by the supramolecular hydrogel. On the basis of such a guest-dependent dynamic redistribution of the receptor molecules, a sophisticated means for molecular recognition of phosphate derivatives can be rationally designed in the hydrogel matrix. That is, the elaborate utilization of the hydrophobic fibrous domains, as well as the water-rich hydrophilic cavities, enables us to establish three distinct signal transduction modes for phosphate sensing: the use of (i) a photoinduced electron transfer type of chemosensor, (ii) an environmentally sensitive probe, and (iii) an artificial receptor displaying a fluorescence resonance energy transfer type of fluorescent signal change. Thus, one can selectively sense and discriminate the various phosphate derivatives, such as phosphate, phospho-tyrosine, phenyl phosphate, and adenosine triphosphate, using a fluorescence wavelength shift and a seesaw type of ratiometric fluorescence change, as well as a simple fluorescence intensity change. It is also shown that an array of the miniaturized hydrogel is promising for the rapid and high-throughput sensing of these phosphate derivatives.     

Electric conductivities of 1:1 electrolytes in liquid methanol along the liquid-vapor coexistence curve up to the critical temperature. III. Tetraalkylammonium bromides

The molar conductivities of the dilute solutions of the tetraalkylammonium bromides have been measured in methanol along the liquid-vapor coexistence curve up to about 180 degrees C. The limiting molar conductivities and the molar association constants have been obtained from the analysis of the concentration dependence of the conductivity. On the basis of the present data together with the literature ones, the validity of the Hubbard-Onsager (HO) dielectric friction theory [J. Hubbard, J. Chem. Phys. 68, 1649 (1978)] derived from the continuum model has been examined for the translational friction coefficients of the tetraalkylammonium ions in methanol in the density range of 0.8232 g cm(-3) > or =rho > or =0.5984 g cm(-3) and the temperature range of -15 degrees C < or =t < or =180 degrees C. At high densities and low temperatures, the observed friction coefficients of Me(4)N(+) and Et(4)N(+) are remarkably smaller than the prediction of the HO theory (where Me stands for methyl group and Et for ethyl group); this kind of limitation of the HO theory has not been recognized for smaller ions, and can be attributed to the loosening of the solvent structure closely related to the weak charge effect for the large ions. The negative deviation from the HO theory gradually disappears with decreasing density and increasing temperature, and the friction coefficients of Me(4)N(+) and Et(4)N(+) are explained by the HO theory reasonably well at low densities and high temperatures. For Pr(4)N(+) and Bu(4)N(+) (where Pr stands for propyl group and Bu for butyl group), the experimental friction coefficients lay in the validity range of the HO theory in all the conditions studied here; the breakdown of the continuum theory at low densities and high temperatures has not been observed in this work. The density dependences of the molar association constants of the tetraalkylammonium bromides are qualitatively explained by the Fuoss theory based on the continuum model.