Effects of Substituents on the Blue Luminescence of Disilane-Linked Donor‒Acceptor‒Donor Triads

A series of disilane-linked donor‒acceptor‒donor triads (D‒Si‒Si‒A‒Si‒Si‒D) was synthesized to investigate the effects of substituents on the photophysical properties. The triads were prepared by metal-catalyzed diiodosilylation of aryl iodides using a Pd(P(t-Bu)3)2/(i-Pr)2EtN/toluene system that we previously developed. Optical measurements, X-ray diffraction analysis, and density functional theory calculations revealed relationships between the photophysical properties and molecular structures of these triads in solution and in the solid state. The compounds emitted blue to green fluorescence in CH2Cl2 solution and in the solid state. Notably, compound 2 showed fluorescence with an absolute quantum yield of 0.17 in the solid state but showed no fluorescence in CH2Cl2. Our findings confirmed that the substituent adjacent to the disilane moiety affects the conformations and emission efficiencies of compounds in solution and in the solid state

Effects of Salinity Stress on the Structure of Bundle Sheath and Mesophyll Chloroplasts in NAD-Malic Enzyme and PCK Type C4 Plants

The effect of NaCl stress on the structure of leaf chloroplasts was investigated in several NAD-Malic enzyme (NAD-ME) and phosphoenolpyruvate carboxykinase (PCK) type C4 plant species. Seedlings of the monocot species, except Zoysia japonica, grown in 300 mL pots were subjected to salt stress by adding 50 mL of 3% NaCl solution per day to the soil for 5 d after the fourth leaf blades were fully developed. Z. japonica and the dicot species, Amaranthus tricolor, were also treated with 3% NaCl in a similar manner from 5 wk after germination. Salt stress negatively affected the growth, chlorophyll content and chloroplast structure in all the species. At the ultrastructure level, swelling of thylakoids and disruption of envelopes were more or less observed in mesophyll cell (MC) chloroplasts after salt treatment. The structure of bundle sheath cell (BSC) chloroplasts, on the other hand, was hardly damaged under salt condition although stromal and starch areas were considerably decreased. Furthermore, salinity induced granal development in BSC chloroplasts in most species; the number of thylakoids per granum, granal indices and appressed thylakoid density in salt-treated plants were generally higher than those in control. Since the similar responses have also been reported in all NADP-ME type C4 species investigated in our previous study, the high sensitivity to salt stress in MC chloroplasts and the granal development in BSC chloroplasts by salinity were considered to be common phenomena in all three C4 subtypes

Salinity Induces Granal Development in Bundle Sheath Chloroplasts of NADP-Malic Enzyme Type C4 Plants

In NADP-malic enzyme (NADP-ME) type C4 plants, MC chloroplasts have well-developed grana, whereas BSC chloroplasts are generally characterized by highly reduced grana. In the previous study, salt treatment induced granal development in BSC chloroplasts of Zea mays, an NADP-ME type C4 plant. Therefore, we examined the effects of salinity stress on the granal structure of BSC chloroplasts in seven other C4 species belonging to the NADP-ME type. The plants were grown in soil and after a certain period of time, they were treated with 3% NaCl for 5 d. Ultrastructure and quantitative properties of chloroplasts at the middle part of leaf tissues were investigated. In BSC chloroplasts of all the C4 species, almost no structural damage was observed, but the development of granal stacking was induced under salinity condition. Granal indices and appressed thylakoid density of BSC chloroplasts in the salt-treated plants were higher than those in the control plants. In all the species, the structure of MC chloroplasts was more or less damaged by salt stress; thylakoids were swollen and chloroplast envelope was disorganized. These results suggest that the granal development in BSC chloroplasts and the high damage of MC chloroplasts are common features of NADP-ME type C4 plants under salinity stress

Confocal Microscopic Evaluation of Mixing Performance for Three-Dimensional Microfluidic Mixer

We developed a confocal microscopic method for a quantitative evaluation of the mixing performance of a three-dimensional microfluidic mixer. We fabricated a microfluidic baker’s transformation (MBT) mixer as a three-dimensional passive-type mixer for the efficient mixing of solutions. Although the MBT mixer is one type of ideal mixers, it is hard to evaluate its mixing performance, since the MBT mixer is based on several cycles of complicated three-dimensional microchannel structures. We applied the method developed here to evaluate the mixing of water and a fluorescein isothiocyanate (FITC; diffusion coefficient, 4.9 × 10−10 m2 s−1) solution by the MBT mixer. This method enables us to capture vertical section images for the fluid distributions of FITC and water at different three-dimensional microchannel structures of the MBT device. These images are in good agreement with those of mixing images based on numerical simulations. The mixing ratio could be calculated by the fluorescence intensity at each pixel of the vertical section image; complete mixing is recognized by a mixing ratio of more than 90%. The mixing ratios are measured at different cycles of the MBT mixer by changing the flow rate; the mixing performance is evaluated by comparisons with the mixing ratio of the straight microchannel without the MBT mixer