A soft on/off switch based on the electrochemically reversible H–J interconversion of a floating porphyrin membrane

Soft molecular assemblies that respond reversibly to external stimuli are attractive materials as on/off switches, in optoelectronic, memory and sensor technologies. In this Edge Article, we present the reversible structural rearrangement of a soft porphyrin membrane under an electrical potential stimulus in the absence of solid-state architectures. The free-floating porphyrin membrane lies at the interface between immiscible aqueous and organic electrolyte solutions and is formed through interfacial self-assembly of zinc(ii) meso-tetrakis(4-carboxyphenyl)porphyrins (ZnPor). A potential difference between the two immiscible electrolyte solutions induces the intercalation of bis(triphenylphosphoranylidene)ammonium cations from the organic electrolyte that exchange with protons in the porphyrin membrane. In situ UV/vis absorbance spectroscopy shows that this ionic intercalation and exchange induces a structural interconversion of the individual porphyrin molecules in the membrane from an H- to a J-type molecular configuration. These structural rearrangements are reversible over 30 potential cycles. In situ polarisation-modulation fluorescence spectroscopy further provides clear evidence of structural interconversion of the porphyrin membrane, as intercalation of the organic electrolyte cations significantly affects the latter''s emissive properties. By adjusting the pH of the aqueous phase, additional control of the electrochemically reversible structural interconversion can be achieved, with total suppression at pH 3.

The structural rearrangement of a porphyrin membrane self-assembled at a “soft” liquid|liquid interface from a H- to J-molecular configuration is reversibly modulated by externally manipulating the interfacial Galvani potential difference.     

Synthesis and biological activities of some new thiazolidine derivatives containing pyrazole ring system

As a part of systematic investigation of synthesis and biologically active compounds of thiazolidine (TZD) derivatives containing pyrazole ring system, several new pyrazole–TZD derivatives 8a , 8b , 8c , 8d and 9a , 9b , 9c , 9d have been synthesized. Compounds 8a , 8b , 8c , 8d were prepared from N‐substituted TZDs 6a , 6b , 6c , 6d and 1H‐pyrazole‐4‐carboxaldehyde 7 by Knoevenagel‐type reaction. Treatment of 8a , 8b , 8c , 8d with sodium hydride at room temperature caused dimerization reaction to afford the corresponding spirocompounds 9a , 9b , 9c , 9d . All the synthesized compounds were characterized by spectroscopic analysis. In vitro, the synthesized compounds 8a , 8b , 8c , 8d and 9a , 9b , 9c , 9d were tested for their growth inhibitory activity in A549 lung cancer, B16F10 murine melanoma, and HeLa human uterine carcinoma cells and for their differentiation of 3T3‐L1 preadipocytes to adipocytes. The results showed that compound 8c possessed growth inhibitory effect of B16F10 cells (IC₅₀ = 27 μM) and compounds 9c , 9d had induction effect on the differentiation of 3T3‐L1 preadipocytes. J. Heterocyclic Chem., (2011).     

Probing molecular structure at interfaces for comparison with bulk solution behavior: water/2-propanol mixtures monitored by vibrational sum frequency spectroscopy

The orientation of the isopropyl group at the liquid/vapor interface in 2-propanol/water binary mixtures was studied by vibrational sum frequency spectroscopy. The CH(3) stretch modes of the two methyl groups were used to determine the molecule's orientation by employing a novel united atom approach to model the (CH(3))(2)X moiety. For this purpose, the changes in the molecular susceptibility of the isopropyl group stretches were derived in the laboratory frame as a function of the tilt and twist angles. The results indicated that the methyl groups lay down on the surface at low alcohol mole fraction and gradually twisted with increasing mole fraction. At the azeotrope, x(iso) = 0.68, one of the methyl groups aligned approximately parallel to the surface normal, whereas the other was nearly parallel with the liquid/vapor interface. When the mole fraction of 2-propanol was higher than 0.68, the orientation of 2-propanol remained almost constant. The change in the alcohol's orientation with 2-propanol mole fraction closely tracked changes in its bulk activity coefficient. Such results lead to a picture in which the surface structure and bulk properties of the system are closely linked.     

Rhodium-catalyzed asymmetric hydroarylation of diphenylphosphinylallenes with arylboronic acids

Rhodium-catalyzed asymmetric hydroarylation of diphenylphosphinylallenes with arylboronic acids proceeded in high yields with high regio- and enantioselectivity to give chiral allylphosphine oxides of up to 98% ee. The structural determination of the key intermediate, a pi-allylrhodium complex, was successful to establish the catalytic cycle of the reaction.     

Suramin is a Novel Activator of PP5 and Biphasically Modulates S100-Activated PP5 Activity

Suramin is an activator of ryanodine receptors and competitively binds to the calmodulin-binding site. In addition, S100A1 and calmodulin compete for the same binding site on ryanodine receptors. We therefore studied the effects of suramin on protein phosphatase 5 (PP5) and S100-activated PP5. In the absence of S100 proteins, suramin bound to the tetratricopeptide repeat (TPR) domain of PP5 and activated the enzyme in a dose-dependent manner. In the presence of S100A2/Ca²⁺, lower concentrations of suramin dose-dependently inhibited PP5 activity as an S100 antagonist, whereas higher concentrations of suramin reactivated PP5. Although the C-terminal fragment of heat shock protein 90 (HspC90) also weakly activated PP5, the binding site of suramin and HspC90 may be different, and addition of suramin showed no clear effect on the phosphatase activity of PP5. Similar biphasic effects of suramin were observed with S100A1-, S100B- or S100P-activated PP5. However, the inhibitory effects of lower concentrations of suramin on S100A6-activated PP5 are weak and high concentrations of suramin further activated PP5. SPR and the cross-linking study showed inhibition of the interaction between S100 protein and PP5 by suramin. Our results revealed that suramin is a novel PP5 activator and modulates S100-activated PP5 activity by competitively binding to the TPR domain.     

Identification of the inclusion complexation between phenyl β-d-(13C6)glucopyranoside and α-cyclodextrin using 2D 1H or 13C DOSY spectrum

This study describes the 2D ¹H and ¹³C diffusion-ordered NMR spectroscopy (DOSY) experiments using the mixed sample of α-cyclodextrin (α-CyD) and phenyl β-d-(¹³C₆)glucopyranoside (1). Both the 2D ¹H and ¹³C DOSY spectra showed the component with a diffusion coefficient different from those of α-CyD and 1, which suggested the inclusion complexation of α-CyD with 1.     

Catalytic asymmetric hydroxylation of α-alkoxycarbonyl amides with a Pr(OPr)3/amide-based ligand catalyst

A catalytic asymmetric hydroxylation of N-nonsubstituted α-alkoxycarbonyl amides is described. A new effective catalyst comprising Pr(OⁱPr)₃ and a fluoro-substituted amide-based ligand was identified using oxaziridine as the oxidizing reagent. The catalyst components were in dynamic equilibrium in the reaction mixture, which assembled to form the associated transition state through metal coordination and hydrogen bonding.     

Experimental and numerical study of mechanism of glass modification process by continuous-wave laser backside irradiation (CW-LBI)

The modification of transparent materials using a femtosecond laser has been studied. We previously proposed a new method of modifying glass using a continuous-wave laser, named continuous-wave laser backside irradiation (CW-LBI), in which CW laser illumination induces a change in the refractive index without cracking the glass. In this study, we investigated the process of glass modification by CW-LBI using time-lapsed imaging and by calculation of the temperature. First, the modification of glass was observed by the shadowgraph method, and it was found that thermal radiation was included in the phenomena that occurred when the glass was modified. Second, the time-lapsed temperature distribution was calculated. The temperature distribution was roughly in accordance with the shape of the modified area observed in the shadowgraphs. We concluded that the radius of the modified area is dependent on the temperature reached in the glass.