Effects of Heterogeneous Mixing of Imidazolium-Based Ionic Liquids with Alcohols on Complex Formation of Ni(II) Ion.

Understanding the complex formation of metal ions in room-temperature ionic liquids (ILs) is essential for the application of ILs in solvent extraction. Nevertheless, the research on metal complex formation in ILs lags behind other applications. The complex formation equilibria may be influenced by specific interactions among the metal ion, ligand molecule, and IL cation and anion.

Characteristic effect of hydroxyurea on the higher-order structure of DNA and gene expression.

Hydroxyurea (HU; hydroxycarbamide) is a chemotherapy medication used to treat various types of cancer and other diseases such as sickle cell anemia. HU inhibits DNA synthesis by targeting ribonucleotide reductase (RNR). Recent studies have suggested that HU also causes oxidative stress in living systems.

Alcohol-Induced Denaturation of Hen Egg White Lysozyme Studied by Infrared, Circular Dichroism, and Small-Angle Neutron Scattering.

In aqueous binary solvents with fluorinated alcohols, 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and aliphatic alcohols, ethanol (EtOH) and 2-propanol (2-PrOH), the denaturation of hen egg white lysozyme (HEWL) with increasing alcohol mole fraction has been investigated in a wide view from the molecular vibration to the secondary and ternary structures. Circular dichroism (CD) measurement showed that the secondary structure of α-helix content of HEWL increases on adding a small amount of the fluorinated alcohol to the aqueous solution, while the β-sheet content decreases. On the contrary, the secondary structure does not significantly change by the addition of the aliphatic alcohols.

Markedly Different Effects of Monovalent Cations on the Efficiency of Gene Expression.

The effect of monovalent cations on a cell-free transcription-translation (TX-TL) system is examined using a luciferase assay. It is found that the potency for all ions analyzed here is in the order Rb  > K  > Cs  > Na  ≈ Li  > (CH ) N , where Rb is most efficient at promoting TX-TL and the ions of Li , Na , and (CH ) N exhibit an inhibitory effect. Similar promotion/inhibition effects are observed for cell-free TL alone with an mRNA template.

Effects of self-hydrogen bonding among formamide molecules on the UCST-type liquid-liquid phase separation of binary solutions with imidazolium-based ionic liquid, [Cmim][TFSI], studied by NMR, IR, MD simulations, and SANS.

The upper critical solution temperature (UCST)-type liquid-liquid phase separation of imidazolium-based ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cmim][TFSI], where represents the alkyl chain length of the cation, = 6, 8, 10, and 12) binary solutions with formamide (FA) was examined as a function of temperature and the FA mole fraction . The two-phase region (immiscible region) of the solutions is much larger and expands more with the increase in , in comparison with the previous [Cmim][TFSI]-1,4-dioxane (1,4-DIO) systems. An array of spectroscopic techniques, including H and C NMR and IR combined with molecular dynamics (MD) simulations, was conducted on the present binary systems to clarify the microscopic interactions that contribute to the phase-separation mechanism.

Anion Effects on the Mixing States of 1-Methyl-3-octylimidazolium Tetrafluoroborate and Bis(trifluoromethylsulfonyl)amide with Methanol, Acetonitrile, and Dimethyl Sulfoxide on the Meso- and Microscopic Scales.

The mixing states of two imidazolium-based ionic liquids (ILs) with different anions, 1-methyl-3-octylimidazolium tetrafluoroborate (CmimBF) and bis(trifluoromethylsulfonyl)amide (CmimTFSA), with three molecular liquids (MLs), methanol (MeOH), acetonitrile (AN), and dimethyl sulfoxide (DMSO), have been investigated on both mesoscopic and microscopic scales using small-angle neutron scattering (SANS), infrared (IR), and H and C nuclear magnetic resonance (NMR) spectroscopy. Additionally, molecular dynamics (MD) simulations have been conducted on the six combinations of ILs and MLs to observe the states of their mixtures on the atomic level. The SANS profiles of the IL-ML mixtures suggested that MeOH molecules only form clusters in both CmimBF and CmimTFSA, whereas AN and DMSO were homogeneously mixed with ILs on the SANS scale.

Assessment of the UCST-type liquid-liquid phase separation mechanism of imidazolium-based ionic liquid, [Cmim][TFSI], and 1,4-dioxane by SANS, NMR, IR, and MD simulations.

Liquid-liquid phase separation of binary systems for imidazolium-based ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cmim][TFSI], where represents the alkyl chain length of the cation), with 1,4-dioxane (1,4-DIO) was observed as a function of temperature and 1,4-DIO mole fraction, . The phase diagrams obtained for [Cmim][TFSI]-1,4-DIO systems showed that the miscible region becomes wider with an increase in the alkyl chain length, . For = 6 and 8, an upper critical solution temperature (UCST) was found.

Direct visualization of local activities of long DNA strands via image-time correlation.

Bacteriophages with long DNA genomes are of interest due to their diverse mutations dependent on environmental factors. By lowering the ionic strength of a hydrophobic (PPh4Cl) antagonistic salt (at 1 mM), single long T4 DNA strand fluctuations were clearly observed, while condensed states of T4 DNA globules were formed above 5-10 mM salt. These long DNA strands were treated with fluorescently labeled probes, for which photo bleaching is often unavoidable over a short time of measurement.

Aggregation of the Dipeptide Leu-Gly in Alcohol-Water Binary Solvents Elucidated from the Solvation Structure for Each Moiety.

The aggregation of a dipeptide, l-leucine-glycine (Leu-Gly), at 100 mmol dm has been observed in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP)-water and 2-propanol (2-PrOH)-water solvents at various alcohol mole fractions, , using the dynamic light scattering technique and molecular dynamics (MD) simulations. Leu-Gly was dissolved into the HFIP solvents at the concentration over the entire range, while the dipeptide was not dissolved in the 2-PrOH solvents above = 0.6.

K+ promotes the favorable effect of polyamine on gene expression better than Na.

Background: Polyamines are involved in a wide variety of biological processes including a marked effect on the structure and function of DNA. During our study on the interaction of polyamines with DNA, we found that K+ enhanced in vitro gene expression in the presence of polyamine more strongly than Na+. Thus, we sought to clarify the physico-chemical mechanism underlying this marked difference between the effects of K+ and Na+.

Mixing states of imidazolium-based ionic liquid, [Cmim][TFSI], with cycloethers studied by SANS, IR, and NMR experiments and MD simulations.

The mixing states of an imidazolium-based ionic liquid (IL), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cmim][TFSI]), with cycloethers, tetrahydrofuran (THF), 1,4-dioxane (1,4-DIO), and 1,3-dioxane (1,3-DIO), have been clarified on the meso- and microscopic scales using small-angle neutron scattering (SANS), IR, and NMR experiments and molecular dynamics (MD) simulations. SANS profiles of [Cmim][TFSI]-THF-d and -1,4-DIO-d solutions at various mole fractions x of molecular liquid (ML) have shown that [Cmim][TFSI] is heterogeneously mixed with THF and 1,4-DIO on the mesoscopic scale, to a high extent in the case of the latter solution. In fact, [Cmim][TFSI] and 1,4-DIO are not miscible with each other above the 1,4-DIO mole fraction x of 0.

Self-Synchronous Swinging Motion of a Pair of Autonomous Droplets.

Synchronized motion between two self-running oil droplets floating on an aqueous phase is reported. We describe the results of our observation on the interference between a pair of centimeter-sized nitrobenzene droplets undergoing back-and-forth motion on a waterway. The two droplets exhibit a swinging type of synchronization when a thin glass capillary is placed at the midpoint of the waterway with a narrow rectangle shape.

Construction of 3D Cellular Composites with Stem Cells Derived from Adipose Tissue and Endothelial Cells by Use of Optical Tweezers in a Natural Polymer Solution.

To better understand the regulation and function of cellular interactions, three-dimensional (3D) assemblies of single cells and subsequent functional analysis are gaining popularity in many research fields. While we have developed strategies to build stable cellular structures using optical tweezers in a minimally invasive state, methods for manipulating a wide range of cell types have yet to be established. To mimic organ-like structures, the construction of 3D cellular assemblies with variety of cell types is essential.

Effects of the long octyl chain on complex formation of nickel(ii) with dimethyl sulfoxide, methanol, and acetonitrile in ionic liquid of [Cmim][TFSA].

In the room-temperature ionic liquid (IL) of 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)amide ([C8mim][TFSA]), the complex formation of Ni2+ with molecular liquids (MLs), dimethyl sulfoxide (DMSO), methanol (MeOH), and acetonitrile (AN), has been examined using ultraviolet (UV)-visible spectroscopy. The overall stability constants log βn, enthalpies , and entropies of the equilibria have been determined to elucidate the mechanism of complex formation. From a comparison of such thermodynamic parameters of the present [C8mim][TFSA] systems with those of the previous systems of 1-ethyl-3-methylimidazolium-based IL, [C2mim][TFSA], the effects of the octyl chain of the imidazolium cation, [C8mim]+, on the complex formation of Ni2+ with MLs have been demonstrated.

Manipulating Living Cells to Construct Stable 3D Cellular Assembly Without Artificial Scaffold.

Regenerative medicine and tissue engineering offer several advantages for the treatment of intractable diseases, and several studies have demonstrated the importance of 3-dimensional (3D) cellular assemblies in these fields. Artificial scaffolds have often been used to construct 3D cellular assemblies. However, the scaffolds used to construct cellular assemblies are sometimes toxic and may change the properties of the cells.

Optical Fluid Pump: Generation of Directional Flow via Microphase Segregation/Homogenization.

We report the successful generation of directional liquid-flow under stationary laser irradiation at a fixed position in a chamber. We adopt a homogeneous solution consisting of a mixture of water and triethylamine (TEA), with a composition near the critical point for phase segregation. When geometrical asymmetry is introduced around the laser focus in the chamber, continuous directional flow is generated, accompanied by the emergence of water-rich microdroplets at the laser focus.

Hydrogen bonds of the imidazolium rings of ionic liquids with DMSO studied by NMR, soft X-ray spectroscopy, and SANS.

The hydrogen bonds of the imidazolium-ring H atoms of ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amides ([Cnmim][TFSA], n = 2 to 12 where n represents the alkyl chain length), with the O atom of dimethyl sulfoxide (DMSO) have been elucidated using 1H, 13C, and 15N NMR spectroscopy and soft X-ray absorption and emission spectroscopy (XAS and XES). Density functional theory (DFT) calculations have been performed on an isolated DMSO molecule and two cluster models of [Cnmim]+-DMSO by hydrogen bonding to interpret the XES spectra for the [Cnmim][TFSA]-DMSO solutions. The 1H and 13C NMR chemical shifts of the imidazolium ring showed that deshielding of the ring H and C atoms is moderate as the DMSO mole fraction xDMSO increases to ∼0.

Spontaneous Oscillations and Synchronization of Active Droplets on a Water Surface via Marangoni Convection.

Shape-oscillations and synchronization are intriguing phenomena in many biological and physical systems. Here, we report the rhythmic mechanical oscillations and synchronization of aniline oil droplets on a water phase, which is induced by Marangoni convection during transfer of the solute. The repetitive increase and decrease in the surface concentration in the vicinity of the contact line leads to the oscillations of droplets through an imbalance in surface tensions.

Manipulating Living Cells to Construct a 3D Single-Cell Assembly without an Artificial Scaffold.

Artificial scaffolds such as synthetic gels or chemically-modified glass surfaces that have often been used to achieve cell adhesion are xenobiotic and may harm cells. To enhance the value of cell studies in the fields of regenerative medicine and tissue engineering, it is becoming increasingly important to create a cell-friendly technique to promote cell⁻cell contact. In the present study, we developed a novel method for constructing stable cellular assemblies by using optical tweezers in a solution of a natural hydrophilic polymer, dextran.

Interfacial interaction and glassy dynamics in stacked thin films of poly(methyl methacrylate).

Neutron reflectivity and dielectric permittivity of alternately stacked thin films of protonated and deuterated poly(methyl methacrylate) were measured to elucidate a correlation between the time evolution of the interfacial structure and the segmental dynamics in the stacked thin polymer films during isothermal annealing above the glass transition temperature. The roughness at the interface between two thin layers increases with the annealing time, whereas the relaxation rate and strength of the α-process decrease with an increase in the annealing time. A strong correlation between the time evolution of the interfacial structure and the dynamics of the α-process during annealing could be observed using neutron reflectivity and dielectric relaxation measurements.

ONO-pincer ruthenium complex-bound norvaline for efficient catalytic oxidation of methoxybenzenes with hydrogen peroxide.

The enhanced catalytic activity of ruthenium complex-bound norvaline Boc-l-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.

Phase Transition and Dynamics in Imidazolium-Based Ionic Liquid Crystals through a Metastable Highly Ordered Smectic Phase.

The phase transition behavior and dynamics of ionic liquid crystals, 1-methyl-3-alkylimidazolium tetrafluoroborate with various alkyl chain lengths, were investigated by X-ray scattering, differential scanning calorimetry, optical microscopy, and dielectric relaxation spectroscopy to elucidate the mechanism of their structural and phase changes. A metastable phase was found to appear via a supercooled smectic phase on cooling. In the metastable phase, disorder in the smectic phase is partially frozen; thus, the phase has order higher than that of the smectic phase but lower than that of the crystalline phase.

Highly Concentrated Ethanol Solutions: Good Solvents for DNA as Revealed by Single-Molecule Observation.

We observed single DNA molecules at different ethanol concentrations by using fluorescence microscopy. Large single DNA molecules undergo reentrant conformational transitions from elongated coil into folded globule and then into elongated coil state, accompanied by the increase of the concentration of ethanol in a low-salt aqueous environment. The second transition from globule into the coil state occurs at around 70 % (v/v) ethanol.

Synthesis and Applications of (ONO Pincer)Ruthenium-Complex-Bound Norvalines.

Two (ONO pincer)ruthenium-complex-bound norvalines, Boc-[Ru(pydc)(terpy)]Nva-OMe (1; Boc=tert-butyloxycarbonyl, terpy=terpyridyl, Nva=norvaline) and Boc-[Ru(pydc)(tBu-terpy)]Nva-OMe (5), were successfully synthesized and their molecular structures and absolute configurations were unequivocally determined by single-crystal X-ray diffraction. The robustness of the pincer Ru complexes and norvaline scaffolds against acidic/basic, oxidizing, and high-temperature conditions enabled us to perform selective transformations of the N-Boc and C-OMe termini into various functional groups, such as alkyl amide, alkyl urea, and polyether groups, without the loss of the Ru center or enantiomeric purity. The resulting dialkylated Ru-bound norvaline, n-C11 H23 CO-l-[Ru(pydc)(terpy)]Nva-NH-n-C11 H23 (l-4) was found to have excellent self-assembly properties in organic solvents, thereby affording the corresponding supramolecular gels.

Solvation dependence of valence electronic states of water diluted in organic solvents probed by soft X-ray spectroscopy.

Knowledge of hydrogen bonds is important in a wide range of scientific fields. However, information on the electronic state of hydrogen bonded molecules in liquids and solutions is still limited. We applied X-ray emission and absorption spectroscopy to observe the electronic state around oxygen of water and investigate the solvent dependence of occupied and unoccupied valence electronic states of water in acetonitrile, 3-methylpyridine, and ethylenediamine at room temperature under atmospheric pressure.