Nematic Liquid-Crystal Necklace Structure Made by Microfluidics System.

We report a necklace structure made of liquid crystal dispersed in poly(vinyl alcohol) (PVA) aqueous solution, which is fabricated by a microfluidic device. In the necklace structure, liquid crystal droplets that are tens of micrometers in diameter are connected by microtethers, which are birefringent, are not penetrating the droplets, and can be elastically stretched by applying external force. The necklace structure was analyzed by fluorescent confocal microscopy, and the tethers were made of liquid crystal and PVA composite. The elastic constant of the tether was determined by using laser tweezers to stretch the tether. The Whispering Gallery Modes circulating inside individual droplets in the necklace structure were also observed.

Effect of the Crystallization Process of Surfactant Bilayer Lamellar Structures on the Elongation of High-Aspect-Ratio Gold Nanorods.

The growth mechanism of an "in-gel synthesis method", that is, the effects of composition and structure of the lamellar gel phase below the Krafft temperature of surfactant solutions on the growth of long gold nanorods, was investigated. We changed the alkyl chain length of surfactant molecules to investigate the effect of surfactant self-assembly on the elongation of gold nanorods systematically; eight mixed solutions of alkyltrimethylammonium bromide (C nTAB; n = 2-16; n = even) with C18TAB were used for investigation. The Krafft temperature, self-assembly of surfactant molecules, and the crystallization process of each mixture were observed by differential scanning calorimetry, wide-angle X-ray scattering, visual inspection, and small-angle X-ray scattering. Gold nanorods were synthesized in these eight surfactant mixtures. These observations demonstrated that when the surfactant Lß phase sustains for a long time, the space of the water layer is also kept large enough for the seeds to take up Au ions bound to surfactant micelles. In this case, the seeds can form long nanorods between bilayers. We conclude that not only the stability of the lamellar gel phase but also co-existence of Au-ion carriers, that is, surfactant micelles, is essential for the elongation of long gold nanorods.

Global genetic response in a cancer cell: self-organized coherent expression dynamics.

Understanding the basic mechanism of the spatio-temporal self-control of genome-wide gene expression engaged with the complex epigenetic molecular assembly is one of major challenges in current biological science. In this study, the genome-wide dynamical profile of gene expression was analyzed for MCF-7 breast cancer cells induced by two distinct ErbB receptor ligands: epidermal growth factor (EGF) and heregulin (HRG), which drive cell proliferation and differentiation, respectively. We focused our attention to elucidate how global genetic responses emerge and to decipher what is an underlying principle for dynamic self-control of genome-wide gene expression. The whole mRNA expression was classified into about a hundred groups according to the root mean square fluctuation (rmsf). These expression groups showed characteristic time-dependent correlations, indicating the existence of collective behaviors on the ensemble of genes with respect to mRNA expression and also to temporal changes in expression. All-or-none responses were observed for HRG and EGF (biphasic statistics) at around 10-20 min. The emergence of time-dependent collective behaviors of expression occurred through bifurcation of a coherent expression state (CES). In the ensemble of mRNA expression, the self-organized CESs reveals distinct characteristic expression domains for biphasic statistics, which exhibits notably the presence of criticality in the expression profile as a route for genomic transition. In time-dependent changes in the expression domains, the dynamics of CES reveals that the temporal development of the characteristic domains is characterized as autonomous bistable switch, which exhibits dynamic criticality (the temporal development of criticality) in the genome-wide coherent expression dynamics. It is expected that elucidation of the biophysical origin for such critical behavior sheds light on the underlying mechanism of the control of whole genome.

Autonomous oscillation of polymer chains induced by the Belousov-Zhabotinsky reaction.

We investigated the self-oscillating behaviors of two types of polymer chains induced by the Belousov-Zhabotinsky (BZ) reaction. One consisted of N-isopropylacrylamide (NIPAAm) and the Ru catalyst of the BZ reaction, and the other consisted of NIPAAm, the Ru catalyst, and acrylamide-2-methylpropanesulfonic acid (AMPS) with a negatively charged domain as a solubility control site. A comparison of the two types of self-oscillation systems showed that the anionic AMPS portion of the polymer chain significantly affected the self-oscillating behavior under strongly acidic condition. The periods of self-oscillation for the two types of self-oscillating polymer chains were investigated by changing the initial concentrations of the three BZ substrates and the temperature. As a result, it was demonstrated that the period of self-oscillation could be controlled by the concentration of the BZ substrates and the temperature. Furthermore, the activation energies of the two types of the self-oscillating polymer chains gave similar values as normal BZ reactions, i.e., not including the self-oscillating polymer system with a Ru moiety. In addition, it was clarified the activation energy was hardly affected by the initial concentration of the three BZ substrates.

Direct observation of periodic swelling and collapse of polymer chain induced by the Belousov-Zhabotinsky reaction.

By utilizing a quartz crystal microbalance with dissipation (QCM-D), we directly observed the self-oscillating behavior of a polymer chain induced by the Belousov-Zhabotinsky (BZ) reaction. We succeeded in measuring self-oscillations of the resonance frequency (Δf) and dissipation (ΔD), which originate in the self-oscillating behavior of the polymer chain on a gold surface induced by the BZ reaction. We synthesized a self-oscillating polymer chain with Ru as the catalyst of the BZ reaction and a chemical adsorption site, so as to directly observe its periodic swelling and collapse on the gold surface. Distinct self-oscillation of ΔD synchronized with the self-oscillation Δf was observed. The period of the Δf self-oscillation was about 400 s, and the induction time was about 6.5 h. In QCM-D measurements, we found that the peaks of Δf and ΔD oscillations did not coincide in time because the state of the Gaussian chain did not coincide with the maximum value of Δf. Moreover, examination of the relationship between Δf and ΔD revealed that their oscillatory waveforms were identical in frequency but differed in phase and amplitude.

Photosystem II antenna phosphorylation-dependent protein diffusion determined by fluorescence correlation spectroscopy.

Flexibility of chloroplast thylakoid membrane proteins is essential for plant fitness and survival under fluctuating light environments. Phosphorylation of light-harvesting antenna complex II (LHCII) is known to induce dynamic protein reorganization that fine-tunes the rate of energy conversion in each photosystem. However, molecular details of how LHCII phosphorylation causes light energy redistribution throughout thylakoid membranes still remain unclear. By using fluorescence correlation spectroscopy, we here determined the LHCII phosphorylation-dependent protein diffusion in thylakoid membranes isolated from the green alga Chlamydomonas reinhardtii. As compared to the LHCII dephosphorylation-induced condition, the diffusion coefficient of LHCII increased nearly twofold under the LHCII phosphorylation-induced condition. We also verified the results by using the LHCII phosphorylation-deficient mutant. Our observation suggests that LHCII phosphorylation-dependent protein reorganization occurs along with the changes in the rate of protein diffusion, which would have an important role in mediating light energy redistribution throughout thylakoid membranes.

Development of multi-environment dual-probe atomic force microscopy system using optical beam deflection sensors with vertically incident laser beams.

We developed a dual-probe atomic force microscopy (DP-AFM) system with two cantilever probes that can be operated in various environments such as in air, vacuum, and liquid. The system employs the optical beam deflection method for measuring the deflection of each cantilever mounted on a probe scanner. The cantilever probes mounted on the probe scanners are attached to inertia sliders, which allow independent control of the probe positions. We constructed three types of probe scanners (tube, shear-piezo, and tripod types) and characterized their performance. We demonstrated AFM imaging in ambient air, vacuum, and ultrapure water, and also performed electrical measurement and pick-up manipulation of a Au nanorod using the DP-AFM system.

Effects of surfactant concentration on formation of high-aspect-ratio gold nanorods.

The effects of surfactant concentration in a growth solution on the elongation of gold nanorods were examined. Gold nanorods were synthesized in solutions with different concentrations of hexadecyltrimethylammonium bromide (HTAB): 100, 200, 300, 400, 500, and 600 mM. The nanorods grown in a solution with higher surfactant concentrations were longer (aspect ratio ~30) than those grown in that with lower concentrations (aspect ratio <10). The self-assembled surfactant structures in the solutions were analyzed using viscosity measurement and small-angle X-ray scattering. These results showed a decrease in the inter-micellar distance with increasing surfactant concentration. Taking the chemical equilibrium for the complex formation between Au ions and HTAB micelles into account, we found that the free Au ion concentration decreases accompanied with the increase in the surfactant concentration. This decrease in the free Au ion concentration suppresses undesirable secondary nucleation of gold crystals in a growth solution, resulting in gold nanorod elongation.

Gelation effect on the synthesis of high-aspect-ratio gold nanorods.

The growth process of high-aspect-ratio gold nanorods in gelled surfactant solution was studied. As for the application of gold nanorods, the surface plasmon is quite useful, whose absorption depends on their aspect ratio. Hence it is important to synthesize gold nanorods with favorable aspect ratio in high yield. For shorter nanorods (aspect ratio < -10), the synthesis and the growth mechanism have been studied well. For the longer nanorods (aspect ratio > -30), however, the growth mechanism has not yet been understood well, although it has been known that the high-aspect-ratio gold nanorods could be synthesized in high yield in gelled surfactant solution. In this paper, we studied the relationship between the growth process of high-aspect-ratio gold nanorods and the gelation of surfactant growth-solution. Small angle X-ray scattering (SAXS) revealed the microscopic feature of gelation as the structural transition of self-assembly of surfactant molecules from micellar to lamellar. These results will be helpful for better understanding on the growth mechanism of high-aspect-ratio gold nanorods.

Salt has a biphasic effect on the higher-order structure of a DNA-protamine complex.

We observed single DNA molecules by fluorescence microscopy to clarify the effect of protamine on their higher-order structure. With an increase in the protamine concentration, the conformation of DNA molecules changes from an elongated coil state to a compact state through an intermediate state. Furthermore, the long-axis length of DNA gradually decreases while maintaining a distribution profile with a single peak. Such behavior is markedly different from the conformational transition of DNA induced by small polyamines such as spermidine and spermine, where individual DNA molecules exhibit an all-or-none transition from a coil to a globule state and the size distribution is characterized by twin peaks around the transition region. Next, we examined the effect of salt on the conformation of the DNA-protamine complex. Interestingly, at a fixed concentration of protamine, DNA tends to shrink with an increase in the NaCl concentration up to 300 mM, and then swells with a further increase in the NaCl concentration, that is, biphasic behavior is generated depending on the salt concentration. For comparison, we examined the effect of salt on DNA compaction induced by the trivalent polyamine spermidine. We confirmed that salt always has an inhibitory effect on spermine-induced compaction. To clarify this biphasic effect of salt on protamine-induced DNA compaction, we performed a numerical simulation on a negatively charged semiflexible polyelectrolyte in the presence of polycations with relatively large numbers of positive charges by taking into account the effect of salt at different concentrations. The results showed that salt promotes compaction up to a certain concentration and then tends to unfold the polyelectrolyte chain, which reproduced the experimental observation in a semiquantitative manner. This biphasic effect is discussed in relation to the specific shielding effect that depends on the salt concentration.

Growth of gold nanorods in gelled surfactant solutions.

Gold nanorods have been actively studied for new nanotechnological materials and industrial applications. It is well known that gold nanorods grow spontaneously in surfactant solutions, and a number of procedures for their preparation have been reported; however, the factors that determine the morphology have not been well understood. In this study, we observed the time series of the growth process of gold nanorods in gelled surfactant solutions by completely stopping the growth reaction. This growth process was compared to that in solution without gelation. The comparison indicates that the self-assembly of surfactant molecules affected the resulting shape, especially the short-axis length, of the nanorods. Small-angle neutron scattering (SANS) experiments revealed that the gelled solutions form lamellar structures, whereas nongelled systems form spherical micelles. On the bases of these results, we present a model showing that the short-axis length of gold nanorods is affected by a decrease in the spontaneous curvature of the outer surfactant layer and/or an increase in the bending modulus of the surfactant membrane neighboring the gold surface.

Analysis of the growth process of gold nanorods with time-resolved observation.

Gold nanorods are generated spontaneously in a surfactant solution. We developed an experimental setup where the growth of gold nanorods can be completely stopped at any instant. With this method, a time series of the growth process of gold nanorods was determined by the direct observation of nanorods with transmission electron microscopy. We estimated the growth rate of nanorods from the change in the average long-axis length over time. To understand the experimental results, we developed a mathematical model for the growth of nanorods. The present results should help to clarify the mechanism of the growth of gold nanorods.

Spatiotemporal pattern in somitogenesis: a non-Turing scenario with wave propagation.

Living organisms maintain their lives under far-from-equilibrium conditions by creating a rich variety of spatiotemporal structures in a self-organized manner, such as temporal rhythms, switching phenomena, and development of the body. In this paper, we focus on the dynamical process of morphogens in somitogenesis in mice where propagation of the gene expression level plays an essential role in creating the spatially periodic patterns of the vertebral columns. We present a simple discrete reaction-diffusion model which includes neighboring interaction through an activator, but not diffusion of an inhibitor. We can produce stationary periodic patterns by introducing the effect of spatial discreteness to the field. Based on the present model, we discuss the underlying physical principles that are independent of the details of biomolecular reactions. We also discuss the framework of spatial discreteness based on the reaction-diffusion model in relation to a cellular array, by comparison with an actual experimental observation.

Evaluation of characteristics and degree of remodeling in coronary atherosclerotic lesions by 64-detector multislice computed tomography (MSCT).

BACKGROUND: Multislice computed tomography (MSCT) permits reliable imaging of not only the coronary artery lumen but also vessel wall. It is assumed that both lipid-rich plaques and those that display positive remodeling are more prone to rupture and erosion with subsequent coronary events. The purpose of this study was to assess the correlation between the characteristics of coronary arteries by MSCT and several measures of coronary heart disease (CHD) risk. METHODS: This study consisted of 424 consecutive participants who received MSCT and coronary angiography (CAG). We assessed coronary artery findings including coronary artery calcification (CAC), degree of remodeling and narrowing of lumen and characteristics including uric acid (UA) and high-sensitivity C-reactive protein (hs-CRP). Statistical analyses were conducted for four subgroups classified by the presence of significant stenosis and positive remodeling. RESULTS: Hs-CRP was 2.10+/-2.70mg/L in positive remodeling (+) and stenosis (+) group (PS), 1.05+/-0.97mg/L in positive remodeling (-) and stenosis (+) group (nPS), 0.94+/-0.88mg/L in positive remodeling (+) and stenosis (-) group (PnS) and 0.44+/-0.49mg/L in positive remodeling (-) and stenosis (-) group (nPnS). The results of logistic regression analysis showed that hs-CRP was higher in PS compared with the other groups (p<0.001) and higher in nPS and PnS compared with nPnS (p<0.05). CONCLUSIONS: Regardless of significant stenosis, positive remodeling by MSCT correlates to the increase of hs-CRP.

Large-scale on-off switching of genetic activity mediated by the folding-unfolding transition in a giant DNA molecule: an hypothesis.

We present a model to describe the on-off switching of transcriptional activity in a genetic assembly by considering the intrinsic characteristics of a giant genomic DNA molecule which can undergo a discrete structural transition between coiled and compact states. We propose a model in which the transition in the higher-order structure of DNA plays an essential role in regulating stable on-off switching and/or the oscillation of a large number of genes under the fluctuations in a living cell, where such a structural transition is caused by environmental factors. This model explains the rapid and broad transcriptional response in a genetic assembly as well as its robustness against fluctuations.

Evaluation of vulnerable coronary plaques and non-alcoholic fatty liver disease (NAFLD) by 64-detector multislice computed tomography (MSCT).

BACKGROUND: Multislice computed tomography (MSCT) permits direct visualization of not only coronary artery stenosis but also the characteristics of plaques in patients with coronary artery disease (CAD). Also, because of its potential to be a novel risk factor for cardiovascular disease, interest in non-alcoholic fatty liver disease (NAFLD) is increasing. METHODS AND RESULTS: Participants comprised 298 consecutive patients who received MSCT to diagnose CAD. Patients with an alcohol intake exceeding 20 g/day or with a history of known liver disease were excluded from the study. Liver steatosis and 4 coronary artery findings, including remodeling lesions, lipid core plaques, calcified plaques and narrowing of lumen, were assessed. Liver steatosis was evaluated by computed tomography density of the liver and spleen. In the study, NAFLD was defined as having a liver and spleen (L:S) ratio of <1.1. The L:S ratios of patients with remodeling lesions or lipid core plaques were significantly lower than those without. NAFLD was related significantly to those findings, but there was no correlation between calcified plaques, narrowing of lumen and L:S ratios. Adjusted odds ratio of NAFLD for remodeling lesions was 2.41 (95% confidence interval (CI), 1.24-4.67; p=0.009), and those for lipid core lesions was 2.29 (95% CI, 1.15-4.56; p=0.018). CONCLUSION: NAFLD is a novel risk factor for vulnerable plaques.

Ultradian oscillations of Stat, Smad, and Hes1 expression in response to serum.

Serum response has been used as a model for studying signaling transduction for many biological events such as cell proliferation and survival. Although expression of many genes is up- or down-regulated after serum stimulation, the Notch effector Hes1 displays oscillatory response. However, the precise mechanism and biological significance of this oscillation remain to be determined. Here, we identified serum-induced ultradian oscillators, including molecules in Stat and Smad signaling. Stat and Smad oscillations involve activation of Stat3 and Smad1 and delayed negative feedback by their inhibitors Socs3 and Smad6, respectively. Moreover, Stat oscillations induce oscillatory expression of Hes1 by regulating its half-life, and loss of Hes1 oscillations leads to G(1) phase retardation of the cell cycle. These results indicate that coupled Stat and Hes1 oscillations are important for efficient cell proliferation and provide evidence that expression modes of signaling molecules affect downstream cellular events.

Real-time imaging of the somite segmentation clock: revelation of unstable oscillators in the individual presomitic mesoderm cells.

Notch signaling components such as the basic helix-loop-helix gene Hes1 are cyclically expressed by negative feedback in the presomitic mesoderm (PSM) and constitute the somite segmentation clock. Because Hes1 oscillation occurs in many cell types, this clock may regulate the timing in many biological systems. Although the Hes1 oscillator is stable in the PSM, it damps rapidly in other cells, suggesting that the oscillators in the former and the latter could be intrinsically different. Here, we have established the real-time bioluminescence imaging system of Hes1 expression and found that, although Hes1 oscillation is robust and stable in the PSM, it is unstable in the individual dissociated PSM cells, as in fibroblasts. Thus, the Hes1 oscillators in the individual PSM cells and fibroblasts are intrinsically similar, and these results, together with mathematical simulation, suggest that cell-cell communication is essential not only for synchronization but also for stabilization of cellular oscillators.

Redetermination of the crystal structure of alpha-copper phthalocyanine grown on KCl.

The crystal structure of a polymorph of copper phthalocyanine (CuPc) grown on a KCl substrate is redetermined by transmission electron diffraction. It has a triclinic unit cell containing one molecule; the crystal does not have a herringbone-type molecular arrangement, which is a common packing mode of planar phthalocyanines. The molecular packing is determined by the diffraction intensity with the aid of the calculation of molecular packing energy. One of the striking features of this polymorph is its stacking mode within a molecular column: the molecular stacking direction projected on a molecular plane is different by an angle of about 45 degrees from that of the alpha-modifications of platinum phthalocyanine (PtPc) and metal-free phthalocyanine (H(2)Pc). A powder X-ray diffraction profile calculated for the polymorph agrees well with that of so-called alpha-CuPc and Rietveld analysis for alpha-CuPc indicates that the CuPc crystals grown on KCl are actually alpha-CuPc; hence, alpha-CuPc is not isostructural with either alpha-PtPc or alpha-H(2)Pc. On the basis of the present results and the reported crystal structures of the planar phthalocyanines that form molecular columns, the polymorphs of the phthalocyanines can be classified into four types distinguished by the molecular stacking mode within the column: alpha(x)-, alpha(+)-, beta(x)- and beta(+)-types.