Time-resolved study on signaling pathway of photoactivated adenylate cyclase and its nonlinear optical response.

Photoactivated adenylate cyclases (PACs) are multidomain BLUF proteins that regulate the cellular levels of cAMP in a light-dependent manner. The signaling route and dynamics of PAC from Oscillatoria acuminata (OaPAC), which consists of a light sensor BLUF domain, an adenylate cyclase domain, and a connector helix (α3-helix), were studied by detecting conformational changes in the protein moiety. Although circular dichroism and small-angle X-ray scattering measurements did not show significant changes upon light illumination, the transient grating method successfully detected light-induced changes in the diffusion coefficient (diffusion-sensitive conformational change (DSCC)) of full-length OaPAC and the BLUF domain with the α3-helix. DSCC of full-length OaPAC was observed only when both protomers in a dimer were photoconverted. This light intensity dependence suggests that OaPAC is a cyclase with a nonlinear light intensity response. The enzymatic activity indeed nonlinearly depends on light intensity, that is, OaPAC is activated under strong light conditions. It was also found that both DSCC and enzymatic activity were suppressed by a mutation in the W90 residue, indicating the importance of the highly conserved Trp in many BLUF domains for the function. Based on these findings, a reaction scheme was proposed together with the reaction dynamics.

Determination Method of Diffusion Coefficient in a Neat Redox-Active Ionic Liquid at a Microdisk Electrode in the Domains Ranging from the Steady-State to Potentiodynamic Near-Steady-State.

In redox-active ionic liquids (RAILs), either or both of the constituent ions are redox-active. Because of the high concentration of the ions, RAILs exhibit not only ion conduction but also electron conduction through the bimolecular electron self-exchange reaction. Because neat RAILs do not contain any supporting electrolyte, migration of the redox active ions results in enhancement or diminishment of the redox current at an electrode. To treat the migration effect for electrochemical analysis, a limiting current correction was theoretically derived by Oldham, Hyk, and Stojek (Oldham, K. J. Electroanal. Chem. 1992, 337, 91-126; Hyk, W.; Stojek, Z. Anal. Chem. 2002, 747, 4805-4813) for the steady-state voltammetry. Although steady-state voltammetry is a robust method in electrochemistry, the actual measurement is time-consuming and cannot be always made because of the instability of the electrochemical system. To overcome the problem, we propose the use of cyclic voltammetry to evaluate the diffusion coefficient of the redox-active ion that constitutes RAIL. The peak currents were analyzed by the purely diffusional framework of the Aoki-Matsuda-Osteryoung equation (Aoki, K.; Akimoto, K.; Tokuda, K.; Matsuda, H.; Osteryoung, J. J. Electroanal. Chem. 1984, 171, 219-230.) in the range from several mV s-1 to several ten mV s-1, and the migration correction to the near-steady-state limiting current was applied on the basis of the Oldham-Hyk-Stojek theory to scale the diffusion coefficient. As an example of RAILs, [FcC6ImC1][TFSI], which exhibits charge increase reaction with the same sign (S+ - e- ⇌ P2+), was used and the cyclic voltammograms were recorded at various sizes of the microdisk electrodes and various scan rates. The peak currents obeyed the Aoki-Matsuda-Osteryoung equation with the scaled diffusion coefficient, which has the same value as determined by the steady-state voltammogram. Our approach can be used to evaluate the diffusion coefficient of redox-active ions that constitute the RAIL with the charge increase reaction with the same sign.

Effects of functional groups of polyfluoroalkyl substances on their removal by nanofiltration.

Determining the reliability of nanofiltration (NF) membranes for the removal of contaminants of emerging concern, including polyfluoroalkyl substances (PFASs), pharmaceuticals, and personal care products (PPCPs), is important for ensuring drinking water safety. This study aimed to clarify the factors that influence the removal of nine major PFASs during submerged NF treatment via extrapolation based on the factors that influence PPCP removal. The rejection of nine PFASs in ultra-filtered dam water by a polypiperazine-amide (NF270) membrane increased from 71 % to 94 % at a low permeate flux of 5 L/m2 h as the PFAS molecular dimensions increased. PFASs with a carboxylic acid (-CO2H) were rejected to a greater extent than PFASs with a sulfo group (-SO3H). Further, negatively charged PFASs or PPCPs were rejected to a greater extent than uncharged and positively charged PPCPs. Our findings suggest that the rejection of PFASs can vary because of the (i) clearance distance between the PFASs' molecular dimensions and NF membrane pore diameter and (ii) intensity of electrostatic repulsion between the PFASs' functional groups and NF membrane surface. Our study indicates that submerged NF can achieve high PFAS rejection; however, variations in rejection among PFASs can become more prominent owing to a low permeate flux.

A redox-active ionic liquid manifesting charge-transfer interaction between a viologen and carbazole and its effect on the viscosity, ionic conductivity, and redox process of the viologen.

Redox-active ionic liquids (RAILs) are gaining attention as a material that can create a wide range of functions. We herein propose a charge-transfer (CT) RAIL by mixing two RAILs, specifically a carbazole-based ionic liquid ([CzC4ImC1][TFSI]) as a donor and a viologen-based ionic liquid ([C4VC7][TFSI]2) as an acceptor. We investigated the effect of CT interaction on the physicochemical properties of the CT ionic liquid (CT-IL) using the results of temperature-dependent measurements of UV-vis absorption, viscosity, and ionic conductivity as well as cyclic voltammograms. We employed the Walden analysis and the Grunberg-Nissan model to elucidate the effect of the CT interaction on the viscosity and ionic conductivity. The CT interaction reduces the viscosity by reducing the electrostatic attraction between the dicationic viologen and TFSI anion. It also reduces the ionic conductivity by the CT association of the dicationic viologen and carbazole. The electrochemically reversible responses of the viologens in [C4VC7][TFSI]2 and CT-IL are consistent with the Nernstian and the interacting two-redox site models. Notably, the transport and electrochemical properties are modulated by CT interaction, leading to unique features that are not present in individual component ILs. The inclusion of CT interaction in RAILs thus provides a powerful means to expand the scope of functionalized ionic liquids.

Effects of a Tailored Brief Behavioral Therapy Application on Insomnia Severity and Social Disabilities Among Workers With Insomnia in Japan: A Randomized Clinical Trial.

Importance: According to the stepped-care model, there is a medium to large effect size for using cognitive behavioral therapy for insomnia that is delivered digitally, such as a smartphone application. However, it has been reported that studies using fully automated cognitive behavioral therapy for insomnia applications without expert support have high dropout rates. Objective: To examine the effects of using a fully automated and individually tailored brief behavior therapy for insomnia (BBTI) applications for 2 weeks on insomnia-related symptoms, social disabilities, and work productivity among workers with insomnia in Japan. Design, Setting, and Participants: This intent-to-treat prospective parallel-group randomized clinical trial included participants 20 years or older with Insomnia Severity Index (ISI) scores of 8 or higher. Participants were recruited via internet advertisements and workplace flyers and randomized to tailored BBTI, standard BBTI, self-monitoring with sleep diaries, or a waiting list control group. The study was conducted from September 21, 2017, to February 23, 2018. Data were analyzed from February 24, 2018, to February 22, 2019. Interventions: A personalized BBTI and standard BBTI intervention, both of which included sleep scheduling, relaxation, sleep hygiene, and sleep diaries, administered via smartphone application. Main Outcomes and Measures: Primary outcomes were insomnia severity, measured using the Japanese version of the Insomnia Severity Index, and social disabilities, measured using the Japanese version of the Sheehan Disability Scale. Secondary outcomes were dysfunctional beliefs, sleep reactivity, and work productivity. All measures were taken before and after the intervention and at 1-month and 3-month follow-ups. Results: A total of 92 participants (mean [SD] age, 42.7 [11.5] years; 60 [65%] men) were randomized and included in analysis, with 24 participants assigned to tailored BBTI, 23 participants assigned to standard BBTI, 23 participants assigned to self-monitoring, and 22 participants assigned to the waiting list control group. At baseline, there were no significant differences among groups on any demographic characteristics or outcome measures. The results of the intent-to-treat analysis showed an interaction effect for all outcome measures. Compared with the waiting list control group, the BBTI interventions were more effective for reduction of insomnia severity (tailored BBTI: Hedges g = -1.64 [95% CI, -2.32 to -0.96]; P < .001; standard BBTI: g = -1.28 [95% CI, -1.93 to -0.63]; P < .001), social disabilities relating to social life (tailored BBTI: g = -1.33 [95% CI, -1.97 to -0.68]; P < .001; standard BBTI: g = -0.84 [95% CI, -1.46 to -0.22]; P = .009), and dysfunctional beliefs (tailored BBTI: g = -1.17 [95% CI, -1.80 to -0.54]; P < .001; standard BBTI: g = -0.84 [95% CI, -1.46 to -0.23]; P = .02) at the 3-month follow-up. Tailored BBTI quickly reduced insomnia severity (1-month follow-up: g = -0.85 [95% CI, -1.46 to -0.24]). Tailored BBTI was only more effective for improvement of work performance (g = -1.09 [95% CI, -1.71 to -0.46]; P = .005), social disabilities related to family life (g = -0.89 [95% CI, -1.51 to -0.28]; P = .005), and sleep reactivity (g = -1.09 [95% CI, -1.72 to -0.46]; P = .007) compared with the waiting list control group at the 3-month follow-up. The tailored BBTI led to improved worker productivity compared with standard BBTI (g = 0.94 [95% CI, 0.33 to 1.55]; P = .01) at the 3-month follow-up. Conclusions and Relevance: These findings suggest that an application for individually tailored BBTI is an inexpensive and effective treatment for insomnia. In future research, it would be informative to investigate the reasons for dropout during the follow-up period. Trial Registration: umin.ac.jp/ctr Identifier: UMIN000036572.

Electrochromism of Ferrocene- and Viologen-Based Redox-Active Ionic Liquids Composite.

Redox-active ionic liquids (RAILs) require no other additional reagents such as solvent and supporting electrolyte for electrochemical reactions under undiluted condition. Viologen-based RAILs are one of the electrochromic (EC) ionic liquids with sharp color contrast and high chemical stability. An operation of an EC cell requires two electroactive elements, an EC material and a charge compensating material. In this study, an equimolar composite of a viologen-based RAIL as the EC material and a ferrocene-based RAIL as the charge compensation material, was synthesized and applied to an EC cell. The EC cell with the composite RAIL of as high concentration as 0.92 M each redox species showed good coloration efficiency (91.4 cm2 C-1 at 540 nm on 1.0 V). The coloration process of the EC cell was diffusion-limited process. The current and absorbance of the EC cell reached constant values at large enough bias voltage because of the charge recombination between reduced viologens and oxidized ferrocenes. The recombination affected rapid color erasing process. Almost no deterioration of the composite RAIL was found by 1H NMR after 13 000 potential cycle durability experiment.

Electrochromism of a bipolar reversible redox-active ferrocene-viologen linked ionic liquid.

A ferrocene-viologen linked "bipolar" type redox-active ionic liquid ([FcC11VC1][TFSI]2) was synthesized as an electrochromic (EC) material that functions without any other additives: solvents, supporting electrolytes and sacrificial agents. The efficiency of a prototype symmetrical EC cell was 70 cm2 C-1 at 1.0 V. The EC process was stable even after over 10 000 potential cycles.

Soluble carbon nanotubes and their applications.

Carbon nanotubes (CNTs) have been the forefront of nanoscience and nanotechnology due to their unique electrical and mechanical properties and specific functions. However, due to their poor solubility in solvents, the applications using the materials have been limited. Therefore, strategic approaches toward the solubilization of CNTs are important in wide fields including chemistry, physics, biochemistry, biology, pharmaceuticals, and medical sciences. In this article, we summarize: (i) the strategic approaches toward the solubilization of CNTs using chemical and physical modifications, (ii) nanocomposites of CNTs and biological molecules including DNA, (iii) formation of CNTs with topological structures, (iv) separation of metallic and semiconducting nanotubes, (v) the preparations of films and fibers of CNTs and hybrid materials of CNTs and organic and inorganic molecules.

Construction and electrochemistry of Langmuir-Blodgett films of fullerene lipid composite/hybrid materials.

Studies of the electrochemistry of Langmuir-Blodgett (LB) films of C70/artificial lipids including tridodecylmethylammonium bromide (3C12N+Br-, 1), didodecylphosphate (2C12PO4H, 2), and dioleoylphosphatidylcholine (DOPC, 3) and of LB films of a fullerene lipid (4) bearing triple alkyl chains on a C60 moiety on electrodes were carried out in aqueous media. Stable Langmuir monolayers of fullerene C70/artificial lipid composites and the fullerene lipid (4) were formed at the air-water interface and these monolayers were transferred onto electrodes as LB films. Here, we focus on the importance of cationic matrix lipid films to the facile electrochemistry of C70 embedded in a LB film of cationic lipids on an electrode in aqueous media. On the basis of the electrolyte dependence and the charge dependence of the matrix lipids, a possible electron-transfer mechanism of the C70/artificial lipid LB film-modified electrodes is presented. Electrochemistry of a LB film of 4 was also obtained in an aqueous medium. We demonstrate that the introduction of the chemistry of lipid bilayer membranes to the LB films of fullerenes guides us toward the construction of fullerene/lipid bilayer devices.

Helical superstructures of fullerene peapods and empty single-walled carbon nanotubes formed in water.

Aqueous dispersions of fullerene C70-filled carbon nanotubes (C70@SWNTs or peapods) and empty single-walled carbon nanotubes (empty SWNTs) were prepared with the aid of trimethyl-(2-oxo-2-pyrene-1-yl-ethyl)-ammonium bromide (1), which is a carbon nanotube solubilizer. This is the first report describing the preparation and characterization of the transparent dispersion/dissolution of the peapods. The UV-vis-near-IR spectra of C70@SWNTs-1 and empty SWNTs-1 were almost identical. We found by means of transmission electron microscopy and atomic force microscopy that the empty SWNTs and C70-peapods form helical nanostructures in the shapes of rings, irregular rings, lassos, handcuffs, catenanes, pseudorotaxanes, and figure-eight structures. The mechanism of the superstructure formation has been discussed in relation to the unique characteristics of stiff polymer chains with the aid of an off-lattice Monte Carlo simulation.

A Fullerene/Lipid Electrode Device: Reversible Electron Transfer Reaction of C60 Embedded in a Cast Film of an Artificial Ammonium Lipid on an Electrode in Aqueous Solution.

Two reversible one-electron transfers are observed for an electrode device made from C60 and an artificial lipid (see schematic drawing). Cyclic voltammetric studies reveal that the redox couples are unchanged even after 50 cycles, thus indicating that the C60 radical monoanion and the C60 dianion generated in aqueous solution are very stable.

Separation of semiconducting single-walled carbon nanotubes by using a long-alkyl-chain benzenediazonium compound.

We designed and synthesized 4-dodecyloxybenzenediazonium tetrafluoroborate (1), which preferentially reacts with metallic single-walled carbon nanotubes (SWNTs) by kinetic control. We first determined the suitable experimental conditions for the preferential reaction of 1 with individually dissolved SWNTs by monitoring the decrease in absorbance for the metallic SWNT in the range of 400-650 nm in the absorption spectrum of the SWNTs. The reacted SWNTs were thoroughly rinsed with THF to obtain THF-insoluble SWNTs. The Raman spectrum of the THF-insoluble SWNTs showed a strong peak near 180 cm(-1), which corresponds to a semiconducting breathing band. The metallic breathing bands (approximately 220 cm(-1)) and Breit-Wingner-Fano (BWF) modes (1520 cm(-1)) corresponding to the metallic SWNTs were much weaker than those of the pristine SWNTs. We also confirmed that metallic peaks in the range of 400-650 nm in the absorption spectrum of THF-insoluble SWNTs that were individually dissolved in an aqueous micelle of sodium cholate were almost nondetectable. All the results indicate that the THF-insoluble SWNTs are semiconducting.

Solubilization of single-walled carbon nanotubes by using polycyclic aromatic ammonium amphiphiles in water--strategy for the design of high-performance solubilizers.

We describe the design of polycyclic aromatic compounds with high performance that dissolve single-walled carbon nanotubes (SWNTs). Synthetic amphiphiles trimethyl-(2-oxo-2-phenylethyl)-ammonium bromide (1) and trimethyl-(2-naphthalen-2-yl-2-oxo-ethyl)-ammonium bromide (2) carrying a phenyl or a naphtyl moiety were not able to dissolve/disperse SWNTs in water. By contrast, trimethyl-(2-oxo-2-phenanthren-9-yl-ethyl)-ammonium bromide (3) solubilized SWNTs, although the solubilization ability was lower than that of trimethyl-(2-oxo-2-pyrene-1-yl-ethyl)-ammonium bromide (4) (solubilization behavior observed by using 4 was described briefly in reference 4a). Transmission electron microscopy (TEM), as well as visible/near-IR, fluorescence, and near-IR photoluminescence spectroscopies were employed to reveal the solubilization properties of 4 in water, and to compare these results with those obtained by using sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HTAB) as solubilizers. Compound 4 solubilized both the as-produced SWNTs (raw-SWNTs) and purified SWNTs under mild experimental conditions, and the solubilization ability was better than that of SDS and HTAB. Near-IR photoluminescence measurements revealed that the chiral indices of the SWNTs dissolved in an aqueous solution of 4 were quite different from those obtained by using micelles of SDS and HTAB; for a SWNTs/4 solution, the intensity of the (7,6), (9,5), and (12,1) indices were strong and the chirality distribution was narrower than those of the micellar solutions. This indicates that the aqueous solution of 4 has a tendency to dissolve semiconducting SWNTs with diameters in the range of 0.89-1.0 nm, which are larger than those SWNTs (0.76-0.97 nm) dissolved in the aqueous micelles of SDS and HTAB.

Self-assembled aggregates and molecular bilayer films of a double-chain fullerene lipid: structure and electrochemistry.

The self-aggregation behavior of C60 fullerenes that bear two octadecyl chains (lipid 1) as well as the structures and electrochemical properties of cast films of 1 are described. We also examined the self-aggregation behavior in organic solvents of three previously reported compounds: C60 with three each of hexadecyl (lipid 2), tetradecyl (lipid 3), or dodecyl (lipid 4) chains. The fullerene lipids in alcohols spontaneously formed spherical aggregates, whose diameters are related to the alkyl-chain lengths, concentrations of the fullerene lipids, and the solvent polarity. The morphologies of the aggregates showed temperature dependence. Cast films of 1 formed multimolecular bilayer structures that undergo a phase transition typical of lipid bilayer membranes. The electrochemistry of cast films of 1 on an electrode in aqueous medium exhibits temperature dependence.

A multi-mode-driven molecular shuttle: photochemically and thermally reactive azobenzene rotaxanes.

The shuttling process of alpha-CyD in three rotaxanes (1-3) containing alpha-cyclodextrin (alpha-CyD) as a ring, azobenzene as a photoactive group, viologen as an energy barrier for slipping of the ring, and 2,4-dinitrobenzene as a stopper was investigated. The trans-cis photoisomerization of 1 by UV light irradiation occurred in both DMSO and water due to the movement of alpha-CyD toward the ethylene group, while the photoisomerization of 2 occurred in DMSO, but not in water. No photoisomerization was observed for 3 in both water and DMSO. The activation parameters of 1 and 1-ref in DMSO are subject to a compensation relation between deltaS(double dagger) and deltaH(double dagger); however, in water, the deltaS(double dagger) terms are not compensated by the deltaH(double dagger) terms. Alternating irradiation of the UV and visible lights resulted in a reversible change in the induced circular dichroism (ICD) bands of trans-1 and cis-1. In contrast, after the UV light irradiation, the ICD band of trans-2 decreased without the appearance of any bands of cis-2. The NMR spectra of 2 in DMSO showed coalescence of the split signals for the methylene and for the viologen protons due to the shuttling of alpha-CyD. Both the NOE differential spectra for cis-1 in water after UV light irradiation and 2 in DMSO after heating to 120 degrees C showed the negative NOE peaks assigned to interior protons of alpha-CyD, suggesting that alpha-CyD in cis-1 exists at the one ethylene moiety, and alpha-CyDs in cis-2 and 2 heated in DMSO exist at the propylene moieties.

Electrochemical fabrication of single-walled carbon nanotubes-DNA complexes by poly(ethylenedioxythiophene) and photocurrent generation by excitation of an intercalated chromophore.

It was found that single-walled carbon nanotubes (SWNTs) solubilized into water by complexation with DNA (salmon testes) can be readily deposited on the ITO electrode by electrochemical oxidative polymerization of ethylenedioxythiophene (EDOT). The driving force for this novel deposition is an electrostatic interaction between the anionic charges of wrapping DNA and the cationic charges of poly(EDOT) formed in the oxidative polymerization process. The presence of poly(EDOT), SWNTs and DNA in the composite was confirmed by measurements of UV-Vis, IR, resonance Raman spectra, cyclic voltammetry (CV) and confocal laser scanning microscopy (CLSM). The composite adsorbed a DNA intercalator (ethidium bromide: EB) very efficiently, which is regarded to be further evidence for inclusion of DNA. The surface morphology, characterized by CLSM, SEM and AFM, featured the network structure consisting of 0.5-ca. 10 microm nanorods. Very interestingly, we found that photoexcitation of EB bound to the DNA generates the photocurrent, indicating that the excited energy of EB is injected into SWNTs, which is collected by the electroconductive poly(EDOT) film on the ITO electrode. We believe, therefore, that the present system is a very convenient method to explore new materials related to redox and photochemical functions.

Structure and electrochemistry of self-organized fullerene-lipid bilayer films.

The unique properties of C(60)-bearing artificial lipids with three C(16) (lipid 1), C(14) (lipid 2), or C(12) (lipid 3) alkyl chains have been characterized by a variety of techniques, including (13)C NMR, UV/Vis, and FT-IR spectroscopies, differential scanning calorimetry (DSC), X-ray diffraction, and electrochemistry. The (13)C NMR and UV/Vis spectra show that the lipids 1-3 have a closed aziridine structure at a 6/6-ring junction of C(60). The DSC data reveal that cast films of 1 exhibit two endothermic peaks at temperature ranges of 35-40 degrees C (main transition) and 47-49 degrees C (subtransition) in air, water, and 0.5 M aqueous tetraethylammonium chloride solution, while cast films of 2 and 3 each display one endothermic peak at 50-57 degrees C. The results of temperature-dependent FT-IR and UV/Vis studies of cast films of 1-3, together with the above data, reveal that the main peak in the DSC thermogram of a film of 1 can be attributed to a typical phase transition as seen in lipid bilayer membranes, while the sub-endothermic peak seen with 1 and the peaks for 2 and 3 stem from a change in the orientation of the C(60) moieties. X-ray diffraction patterns of each of the cast films of 1-3 show a diffraction peak corresponding to the (001) plane, suggesting the formation of molecular bilayer membrane structures. Cyclic voltammograms and Osteryoung square-wave voltammograms obtained from cast films of 1-3 on basal plane pyrolytic graphite (BPG) electrodes show strong temperature dependences. Finally, the thermodynamics of the binding of nine different alkylammonium ions and two alkylphosphonium ions to the electrogenerated radical monoanions and dianions of 1-3 cast on electrodes is described.