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 xA 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 ß-sheet content decreases. On the contrary, the secondary structure does not significantly change by the addition of the aliphatic alcohols. Correspondingly, the infrared (IR) spectroscopic measurements revealed that the amide I band red-shifts on the addition of the fluorinated alcohol. However, the band remains unchanged in the aliphatic alcohol systems with increasing alcohol content. To observe the ternary structure of HEWL, small-angle neutron scattering (SANS) experiments with H/D substitution technique have been applied to the HEWL solutions. The SANS experiments were successful in revealing the details of how the geometry of the HEWL changes as a function of xA. The SANS profiles indicated the spherical structure of HEWL in all of the alcohol systems in the xA range examined. The mean radius of HEWL in the two fluorinated alcohol systems increases from ∼16 to ∼18 Å during the change in the secondary structure against the increase in the fluorinated alcohol content. On contrast, the radius does not significantly change in both aliphatic alcohol systems below xA = 0.3 but expands to ∼19 Å as the alcohol content is close to the limitation of the HEWL solubility. According to the present results, together with our knowledge of the alcohol cluster formation and the interaction of the trifluoromethyl (CF3) groups with the hydrophobic moieties of biomolecules, the effects of alcohols on the denaturation of the protein have been discussed on a molecular scale.

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+  > (CH3 )4 N+ , where Rb+ is most efficient at promoting TX-TL and the ions of Li+ , Na+ , and (CH3 )4 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, [Cnmim][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 ([Cnmim][TFSI], where n represents the alkyl chain length of the cation, n = 6, 8, 10, and 12) binary solutions with formamide (FA) was examined as a function of temperature and the FA mole fraction xFA. The two-phase region (immiscible region) of the solutions is much larger and expands more with the increase in n, in comparison with the previous [Cnmim][TFSI]-1,4-dioxane (1,4-DIO) systems. An array of spectroscopic techniques, including 1H and 13C 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. The hydrogen-bonding interactions of the imidazolium ring H atoms are more favorable with the O atoms of the FA molecules than with 1,4-DIO molecules, whereas the latter interact more favorably with the alkyl chain of the cation. Upon lowering the temperature, the FA molecules gradually self-aggregate through self-hydrogen bonding to form FA clusters. Concomitantly, clusters of ILs are formed via the electrostatic interaction between the counter ions and the dispersion force among the IL alkyl chains. Small-angle neutron scattering (SANS) experiments on the [C6mim][TFSI]-FA-d2 and [C8mim][TFSI]-FA-d2 systems revealed, similarly to [Cnmim][TFSI]-1,4-DIO systems, the crossover of the mechanism from the 3D-Ising mechanism around the UCST xFA to the mean-field mechanism at both sides of the mole fraction. Interestingly, the xFA range of the 3D-Ising mechanism for the FA systems is wider compared with the range of the 1,4-DIO systems. In this way, the self-hydrogen bonding among FA molecules most significantly governs the phase equilibria of the [Cnmim][TFSI]-FA systems.

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 (C8mimBF4) and bis(trifluoromethylsulfonyl)amide (C8mimTFSA), 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 1H and 13C 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 C8mimBF4 and C8mimTFSA, whereas AN and DMSO were homogeneously mixed with ILs on the SANS scale. MeOH clusters are more enhanced in BF4--IL than TFSA--IL. The microscopic interactions among IL cations, anions, and MLs should contribute to the mesoscopic mixing states of the IL-ML mixtures. In fact, the IL cation-anion, cation-ML, anion-ML, and ML-ML interactions observed by IR, NMR, and MD simulations clarified the reasons for the mixing states of the IL-ML binary solutions observed by the SANS experiments. In neat ILs, the imidazolium ring of the IL cation more strongly interacts with BF4- than TFSA- due to the higher charge density of the former. The interaction of anions with the imidazolium ring is more easily loosened on adding MLs to ILs in the order of DMSO > MeOH > AN. It does not significantly depend on the anions. However, the replacement of the anion on the imidazolium ring by an ML depends on the anions; the replacement is more proceeded in the order of MeOH > DMSO > AN in BF4--IL, while DMSO > MeOH > AN in TFSA--IL. On the other hand, the solvation of both anions by MLs is stronger in the order of MeOH > DMSO ≈ AN. Despite the stronger interactions of MeOH with both cations and anions, MeOH molecules are heterogeneously mixed with both ILs to form clusters in the mixtures. Therefore, the self-hydrogen bonding among MeOH molecules most markedly governs the mixing state of the binary solutions among the abovementioned interactions.

Assessment of the UCST-type liquid-liquid phase separation mechanism of imidazolium-based ionic liquid, [C8mim][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 ([Cnmim][TFSI], where n 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, x1,4-DIO. The phase diagrams obtained for [Cnmim][TFSI]-1,4-DIO systems showed that the miscible region becomes wider with an increase in the alkyl chain length, n. For n = 6 and 8, an upper critical solution temperature (UCST) was found. To clarify the mechanism of the UCST-type phase separation, small-angle neutron scattering (SANS) experiments were conducted on the [C8mim][TFSI]-1,4-DIO-d8 system at several x1,4-DIO. The critical exponents of γ and ν determined from the SANS experiments showed that phase separation of the system at the UCST mole fraction occurs via the 3D-Ising mechanism, while that on both sides of UCST occurs via the mean field mechanism. Thus, the crossover of mechanism was observed for this system. The microscopic interactions among the cation, anion, and 1,4-DIO were elucidated using 1H and 13C NMR and IR spectroscopic techniques, together with the theoretical method of molecular dynamics (MD) simulations. The results on the microscopic interactions suggest that 1,4-DIO molecules cannot strongly interact with H atoms on the imidazolium ring, while they interact with the octyl chain of the cation through dispersion force. With a decrease in temperature, 1,4-DIO molecules gradually aggregate to form 1,4-DIO clusters in the binary solutions. The strengthening of the C-H⋯O interaction between 1,4-DIO molecules by cooling is the key to the phase separation. Of course, the electrostatic interaction between the cations and anions results in the formation of IL clusters. When IL clusters are excluded from 1,4-DIO clusters, liquid-liquid phase separation occurs. Accordingly, the balance between the electrostatic force between the cations and anions and the C-H⋯O interaction between the 1,4-DIO determines the 3D-Ising or the mean field mechanism of phase separation.

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. In addition, long (few tens of [Formula: see text]) length scales are required to have larger fields of view for better sampling, with shorter temporal resolutions. Thus, an optimization between length and time is crucial to obtain useful information. To facilitate the challenge of detecting large biomacromolecules, we here introduce an effective method of live image data analysis for direct visualization and quantification of local thermal fluctuations. The motions of various conformations for the motile long DNA strands were examined for the single- and multi-T4 DNA strands. We find that the unique correlation functions exhibit a relatively high-frequency oscillatory behavior superimposed on the overall slower decay of the correlation function with a splitting of amplitudes deriving from local activities of the long DNA strands. This work shows not only the usefulness of an image-time correlation for analyzing large biomacromolecules, but also provides insight into the effects of a hydrophobic antagonistic salt on active T4 bacteriophage long DNA strands, including thermal translocations in their electrostatic interactions.

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-3 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, xA, 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 xA range, while the dipeptide was not dissolved in the 2-PrOH solvents above xA = 0.6. Interestingly, the MD snapshots showed different shapes of Leu-Gly aggregates in the HFIP and 2-PrOH solvents. A linear-shaped aggregate forms in the former; in contrast, a spherical-shaped aggregate is generated in the latter. The solvation structure of each moiety of Leu-Gly in the HFIP and 2-PrOH solvents was observed using experimental and theoretical techniques,1H and 13C NMR, IR, and 19F-1H HOESY measurements and MD simulations. These results gave us the reasons for the different shapes of Leu-Gly aggregates in both solvents. In the HFIP solvents, most of the moieties of the dipeptide are easily solvated by HFIP. This induces the elongated structure of Leu-Gly, leading to the electrostatic interaction between the N- (NH3+ group) and C- (COO- group) terminals of dipeptide molecules. On the other hand, in the 2-PrOH solvents, water molecules that initially solvate the moieties of Leu-Gly, such as the N- and C-terminals and the peptide linkage, are not easily eliminated even as the xA is close to 0.6. The water molecules can bridge such moieties of Leu-Gly to form spherical-shaped aggregates. The diffusion coefficients of Leu-Gly in both alcohol-water binary solvents were experimentally determined by NMR DOSY to estimate the geometries of the aggregates in the solvents. The sizes of Leu-Gly aggregates obtained by DOSY for both solvent systems were consistent with those estimated from the MD snapshots.

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+. PRINCIPAL FINDINGS: It was found that K+ enhanced gene expression in the presence of spermidine, SPD(3+), much more strongly than Na+, through in vitro experiments with a Luciferase assay on cell extracts. Single-DNA observation by fluorescence microscopy showed that Na+ prevents the folding transition of DNA into a compact state more strongly than K+. 1H NMR measurement revealed that Na+ inhibits the binding of SPD to DNA more strongly than K+. Thus, SPD binds to DNA more favorably in K+-rich medium than in Na+-rich medium, which leads to favorable conditions for RNA polymerase to access DNA by decreasing the negative charge. CONCLUSION AND SIGNIFICANCE: We found that Na+ and K+ exhibit markedly different effects through competitive binding with a cationic polyamine, SPD, to DNA, which causes a large difference in the higher-order structure of genomic DNA. It is concluded that the larger favorable effect of Na+ than K+ on in vitro gene expression observed in this study is well attributable to the significant difference between Na+ and K+ on the competitive binding inducing conformational transition of DNA.

Mixing states of imidazolium-based ionic liquid, [C4mim][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 ([C4mim][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 [C4mim][TFSI]-THF-d8 and -1,4-DIO-d8 solutions at various mole fractions xML of molecular liquid (ML) have shown that [C4mim][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, [C4mim][TFSI] and 1,4-DIO are not miscible with each other above the 1,4-DIO mole fraction x1,4-DIO of 0.903, whereas the IL can be mixed with THF over the entire range of THF mole fraction xTHF. The results of IR and 1H and 13C NMR measurements and MD simulations showed that cycloether molecules are more strongly hydrogen-bonded with the imidazolium ring H atoms in the order of THF > 1,3-DIO > 1,4-DIO. Although 1,4-DIO and 1,3-DIO molecules are structural isomers, our results point out that 1,4-DIO cannot be strongly hydrogen-bonded with the ring H atoms. The solvation of [TFSI]- by cycloethers through the dipole-dipole interaction promotes hydrogen bonding between the ring H atoms and cycloethers. Thus, 1,4-DIO with the lowest dipole moment cannot easily eliminate [TFSI]- from the imidazolium ring. This results in the weakest hydrogen bonds of 1,4-DIO with the ring H atoms. 2D-NMR of 1H{1H} rotating-frame nuclear Overhauser effect spectroscopy (ROESY) showed the interaction of the three cycloethers with the butyl group of [C4mim]+. 1,4-DIO mainly interacts with the butyl group by the dispersion force, whereas THF interacts with the IL by both hydrogen bonding and dispersion force. This leads to the higher heterogeneity of the 1,4-DIO solutions compared to the THF solutions.

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. Furthermore, 2:1 synchronized oscillation of the periodicities of this back-and-forth motion is generated when the capillary is shifted away from the center of the waterway. We discuss the mechanism of the emergence of synchronized swinging motion for the pair of droplets based on a simple mathematical model with nonlinear coupled differential equations.

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. Our recent studies have shown that the presence of nonspecific soluble polymers in aqueous solution is the key to creating stable 3D cellular assemblies efficiently. The present study further expands on the construction of 3D single cell assemblies using two different cell types. We have successfully generated 3D cellular assemblies, using GFP-labeled adipose tissue-derived stem cells and endothelial cells by using optical tweezers. Our findings will support the development of future applications to further characterize cellular interactions in tissue regeneration.

Effects of the long octyl chain on complex formation of nickel(ii) with dimethyl sulfoxide, methanol, and acetonitrile in ionic liquid of [C8mim][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 ßn, 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. In [C8mim][TFSA]-ML systems, more stable complexes are formed with MLs in the sequence of AN > DMSO ≫ MeOH. This sequence differs from that of DMSO ≫ AN > MeOH in [C2mim][TFSA]. For the AN systems, the stabilities of [Ni(an)n] in [C8mim][TFSA] are higher as compared to those in [C2mim][TFSA]. In contrast, for the DMSO systems, [Ni(dmso)n] is less stable in the IL with the longer alkyl chain than that in the IL with the shorter chain. The dependence of the alkyl chain length on the stabilities of [Ni(meoh)n] is the least significant among the three MLs. These varieties of the stabilities of Ni2+ complexes with the MLs have been interpreted from the thermodynamic parameters, together with the static interactions in the [C8mim][TFSA]-ML and [C2mim][TFSA]-ML solvents observed by means of 1H and 13C NMR, small-angle neutron scattering (SANS), and infrared (IR) with an ATR diamond prism.

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. Thus, it would be beneficial to establish a non-toxic method for facilitating cell-cell contact. In this paper, we introduce a novel method for constructing stable cellular assemblies by using optical tweezers with dextran. One of the advantages of this method is that it establishes stable cell-to-cell contact within a few minutes. This new method allows the construction of 3D cellular assemblies in a natural hydrophilic polymer and is expected to be useful for constructing next-generation 3D single-cell assemblies in the fields of regenerative medicine and tissue engineering.

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. The emerging microdroplets tend to escape toward the surrounding bulk solution and then merge/annihilate into the homogeneous solution. The essential features of the directional flow are reproduced through a simple numerical simulation using fluid dynamic equations.

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 ∼0.8; however, it becomes more significant with further increase of xDMSO. This finding suggests that the hydrogen bonds of the three ring H atoms with the DMSO O atoms are saturated in solutions with xDMSO increased to ∼0.8. The 1H and 13C chemical shifts of the alkyl chains revealed that the electron densities of the chain H and C atoms gradually decrease with increasing xDMSO, except for the N1-bound carbon atom C7 of the chain. The 15N NMR chemical shifts showed that the imidazolium-ring N1 atom which is bound to the alkyl chain is shielded with increasing xDMSO in the range from 0 to 0.8 and is then deshielded with further increase of xDMSO. In contrast, the imidazolium ring N3 atom is simply deshielded with increasing xDMSO. Thus, the electron densities of the alkyl chain may be condensed at the C7 and N1 atoms of [Cnmim]+ by the hydrogen bonding of the ring H atoms with DMSO. The hydrogen bonding of DMSO with the ring results in low-energy shifts of the XES peaks of the O K-edge of DMSO. Small-angle neutron scattering experiments showed that [Cnmim][TFSA] and DMSO are homogeneously mixed with each other on the mesoscopic scale. This results from the strong hydrogen bonds of DMSO with the imidazolium-ring H atoms.

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. The nature of the oscillations depends on the diameter of the droplet, the depth of the bulk aqueous phase, and the concentration of the aqueous phase. A numerical simulation reproduces the essential behaviors of active oscillations of a droplet. Droplets sense each other through a surface tension gradient and advection, and hydrodynamic coupling in the bulk solution induces the synchronization of droplet oscillations.

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.

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. In this method, a target cell is transferred to another target cell to make cell⁻cell contact by optical tweezers in a culture medium containing dextran. When originally non-cohesive cells are held in contact with each other for a few minutes under laser trapping, stable cell⁻cell adhesion is accomplished. This method for creating cellular assemblies in the presence of a natural hydrophilic polymer may serve as a novel next-generation 3D single-cell assembly system with future applications in the growing field of regenerative medicine.

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. During the subsequent heating process, the frozen disorder activates, and a crystalline phase appears in the supercooled smectic phase before entering the smectic phase. The relationship between the phase behavior and the dynamics of charge carriers such as ions is also discussed.