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The nucleation rate of tetragonal hen egg white (HEW) lysozyme crystals could be increased or decreased via application of an ac electric field, which modifies the chemical potential of the liquid and solid states. The strength of an external electric field necessary to control the nucleation rate was calculated to be 104−105V/cm, which was larger than that used experimentally by 2 or 3 orders of magnitude. This huge discrepancy could be understood by assuming the presence of a very large electric field sustained in the electric double layer (EDL) that forms at the interface between the dissimilar phases. By changing the frequency of an applied electric field of 800 V/cm in the range of 1−9 MHz, we were able to increase or decrease the nucleation rate. Specifically, the nucleation rate with an applied electric field increased with an increasing applied frequency up to 5 MHz and then significantly dropped above this value. The rapid decrease is considered to result from extinction of the EDL above 5 MHz. [ABSTRACT FROM AUTHOR]

Although thin-film composite membranes have achieved great success in CO 2 separation, further improvements in the CO 2 permeance are required to reduce the size and cost of the CO 2 separation process. Herein, we report the fabrication of composite membranes with high CO 2 permeability using a laser-patterned porous membrane as the support membrane. High-aspect-ratio micropatterns with well-defined micropores on their surface were carved on microporous polymer supports by a direct laser writing process using a short-pulsed laser. By using a Galvano scanner and optimizing the laser conditions and target materials, in-plane micropatterns, such as microhole arrays, microline grating, microlattices, and out-of-plane hierarchical micropatterns, were created on porous membranes. An aqueous suspension of hydrogel microparticles doped with an amine-based mobile carrier was sprayed onto the patterned surface to form a defect-free thin separation layer. The surface area of the separation layer on the patterned support is up to 80% larger than that of flat pristine membranes, resulting in a 52% higher CO 2 permeance (1106 GPU) with a CO 2 /N 2 selectivity of 172. The laser-patterned porous membranes allow the development of inexpensive and high-performance functional membranes not only for CO 2 separation but also for other applications, such as water treatment, cell culture, micro-TAS, and membrane reactors.

Inside cells, various biological systems work cooperatively for homeostasis and self-replication. These systems do not work independently as they compete for shared elements like ATP and NADH. However, it has been believed that such competition is not a problem in codependent biological systems such as the energy-supplying glycolysis and the energy-consuming translation system. In this study, we biochemically reconstituted the coupling system of glycolysis and translation using purified elements and found that the competition for ATP between glycolysis and protein synthesis interferes with their coupling. Both experiments and simulations revealed that this interference is derived from a metabolic tug-of-war between glycolysis and translation based on their reaction rates, which changes the threshold of the initial substrate concentration for the success coupling. By the metabolic tug-of-war, translation energized by strong glycolysis is facilitated by an exogenous ATPase, which normally inhibits translation. These findings provide chemical insights into the mechanism of competition among biological systems in living cells and provide a framework for the construction of synthetic metabolism in vitro.

Staphylococcus aureus α-hemolysin (αHL) is one of the most popular proteins in nanopore experiments within lipid membranes. Higher concentrations of αHL within the lipid membrane are desirable to enhance the mass transport capacity through nanopores. However, the reconstitution of αHL at high concentrations is associated with the problem of membrane lytic disruption. In this study, we present a method that effectively increases αHL concentration while maintaining membrane stability. This method is achieved by using phase-separated giant liposomes, where coexisting liquid-disordered (Ld) and liquid-ordered phases (Lo) are enriched in unsaturated lipids and saturated lipids with cholesterol (Chol), respectively. Fluorescence observation of αHL in liposomes revealed that the presence of Chol facilitates αHL insertion into the membrane. Despite the preferential localization of αHL in the Ld phase rather than the Lo phase, the coexistence of both Lo and Ld phases prevents membrane disruption in the presence of concentrated αHL. We have explained this stabilization mechanism considering the lower membrane tension exhibited by phase-separated liposomes compared to homogeneous liposomes. Under hypertonic conditions, we have successfully increased the local concentration of αHL by invagination of the lipid-only region in the Ld phase, leaving αHL behind. This method exhibits potential for the reconstitution of various nanochannels and membrane proteins that prefer the Ld phase over the Lo phase, thus enabling the production of giant liposomes at high concentrations and the replication of the membrane-crowding condition observed in cells.

Lubricants with desirable frictional properties are important in achieving an energy-saving society. Lubricants at the interfaces of mechanical components are confined under high shear rates and pressures and behave quite differently from the bulk material. Computational approaches such as nonequilibrium molecular dynamics (NEMD) simulations have been performed to probe the molecular behavior of lubricants. However, the low-shear-velocity regions of the materials have rarely been simulated owing to the expensive calculations necessary to do so, and the molecular dynamics under shear velocities comparable with that in the experiments are not clearly understood. In this study, we performed NEMD simulations of extremely confined lubricants, i.e., two molecular layers for four types of lubricants confined in mica walls, under shear velocities from 0.001 to 1 m/s. While we confirmed shear thinning, the velocity profiles could not show the flow behavior when the shear velocity was much slower than thermal fluctuations. Therefore, we used an unsupervised machine learning approach to detect molecular movements that contribute to shear thinning. First, we extracted the simple features of molecular movements from large amounts of MD data, which were found to correlate with the effective viscosity. Subsequently, the extracted features were interpreted by examining the trajectories contributing to these features. The magnitude of diffusion corresponded to the viscosity, and the location of slips that varied depending on the spherical and chain lubricants was irrelevant. Finally, we attempted to apply a modified Stokes-Einstein relation at equilibrium to the nonequilibrium and confined systems. While systems with low shear rates obeyed the relation sufficiently, large deviations were observed under large shear rates.

Reaction-diffusion (RD) waves, which are dynamic self-organization structures generated by nanosize molecules, are a fundamental mechanism from patterning in nano- and micromaterials to spatiotemporal regulations in living cells, such as cell division and motility. Although the periods of RD waves are the critical element for these functions, the development of a system to control their period is challenging because RD waves result from nonlinear physical dynamics under far-from-equilibrium conditions. Here, we developed an artificial cell system with tunable period of an RD-driven wave (Min protein wave), which determines a cell division site plane in living bacterial cells. The developed system is based on our finding that Min waves are generated by energy consumption of either ATP or dATP, and the period of the wave is different between these two energy suppliers. We showed that the Min-wave period was modulated linearly by the mixing ratio of ATP and dATP and that it was also possible to estimate the mixing ratio of ATP and dATP from the period. Our findings illuminated a previously unidentified principle to control the dissipative dynamics of biomolecules and, simultaneously, built an important framework to construct molecular robots with spatiotemporal units.

Polymer micromaterials in a liquid or gel phase covered with a surfactant membrane are widely used materials in pharmaceuticals, cosmetics, and foods. In particular, cell-sized micromaterials of biopolymer solutions covered with a lipid membrane have been studied as artificial cells to understand cells from a physicochemical perspective. The characteristics and phase transitions of polymers confined to a microscopic space often differ from those in bulk systems. The effect that causes this difference is referred to as the cell-size space effect (CSE), but the specific physicochemical factors remain unclear. This study introduces the analysis of CSE on molecular diffusion, nanostructure transition, and phase separation and presents their main factors, i.e., short- and long-range interactions with the membrane surface and small volume (finite element nature). This serves as a guide for determining the dominant factors of CSE. Furthermore, we also introduce other factors of CSE such as spatial closure and the relationships among space size, the characteristic length of periodicity, the structure size, and many others produced by biomolecular assemblies through the analysis of protein reaction-diffusion systems and biochemical reactions.

Resolvins are pro-resolving lipid mediators with highly potent anti-inflammatory effects. Because of their polyunsaturated structures, however, they are unstable to oxygen as a drug prototype. To address this issue, we designed and synthesized CP-RvE3 as oxidatively stable congeners of RvE3 by replacing the cis -olefin with a cis -cyclopropane to avoid the unstable bisallylic structure. Although the oxidative stabilities of CP-RvE3 were not improved, β-CP-RvE3 was 3.7 times more metabolically stable than RvE3. Thus, we identified β-CP-RvE3 as a metabolically stable equivalent.

Epitaxial growth is one of the most important techniques for the control of crystal growth, especially for growing thin-film semiconductor crystals. Similarly, colloidal epitaxy, a template-assisted self-assembly method, is a powerful technique for controlling the structure of colloidal crystals. In this study, heteroepitaxial growth, which differs from homoepitaxial growth of conventional colloidal epitaxy, using foreign colloidal crystals as a substrate, was used to grow single-component colloidal crystal films. The Frank-van der Merwe (FM), Stranski-Krastanov (SK), and Volmer-Weber (VW) modes were observed, and the mode varied with the lattice-misfit ratio and interparticle interactions between the substrate and epitaxial phase. The transition of the growth mode (from SK to VW) and the coexistence of different growth modes (FM and VW) were observed, and their processes were revealed by in situ observation. Colloidal heteroepitaxy was confirmed to be useful for controlling structure, which will enable exploration of novel colloidal self-assembly structures.

Novel γ-aminobutyric acid (GABA) analogues 3 - 5 , having a bicyclo[3.1.0]hexene, [4.1.0]heptane, or [4.1.0]heptene backbone, respectively, were designed from the bioactive form analysis of the previous inhibitor 2 with a bicyclo[3.1.0]hexane backbone. Compounds 3 - 5 and 2 were synthesized from a common 1,7-diene intermediate 6 using ring-closing metathesis (RCM) to construct the key bicyclo backbones. Compounds 3 - 5 strongly inhibit betaine/GABA transporter 1 (BGT1) uptake, but compound 4 stands out with its selective low micromolar potency.

The structure of the water layer between the ice interface and the hydroxylated amorphous/crystalline silica surfaces was investigated using molecular dynamics simulations. The results indicate that the density profile in the direction perpendicular to the surface has two density peaks in the water layer at the ice-silica interface, which are affected by the silanol group density on the wall and the degree of supercooling in the system. In the two density peaks, the one facing the ice interface side has the same structure as the ice crystal, while the other density peak facing the silica surface has an icelike structure. In the solidification process, the ice and icelike structures in the layer progress more on the amorphous silica surface where the density of the silanol groups is low. The relationship between the ice crystallization and the thickness of the layer has been studied in detail; the lower the temperature, the more the ice crystallization progresses and the thinner the layer becomes.

Quantification of pg/L levels (i.e., 0.6 mBq/L) of radioactive technetium-99 ( 99 Tc) was achieved within 15 min in the presence of isobaric and polyatomic interference sources such as ruthenium-99 ( 99 Ru) and molybdenum hydride ( 98 Mo 1 H) at 3-11 orders of magnitude higher concentrations. Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) with oxygen (O 2 ) dynamic reaction cell (online SPE-ICP-MS-DRC) was shown to be a thorough automatic analytical system, circumventing the need for human handling. At three stepwise separations (SPE-DRC-Q mass filters), we showed that interference materials allowed the coexistence of abundance ratios of 1.5 × 10 -13 and 1.1 × 10 -5 for 99 Tc/Mo and 99 Tc/Ru, respectively. A classical mathematical correction using the natural isotope ratio of 99 Ru/ 102 Ru was used to calculate the residues of 99 Ru. Using this optimized system, a detection limit (DL; 3σ) of 99 Tc was 9.3 pg/L (= 5.9 mBq/L) for a 50 mL injection and sequential measurements were undertaken at a cycle of 24 min/sample. For the measurement of a lower concentration of 99 Tc, an AG1-X8 anion-exchange column was used to study 20 L of seawater. Its DL was approximately 1000 times greater than that of previous methods (70.0 fg/L). Thus, this method withstands coexistences of 5.8 × 10 -18 and 3.5 × 10 -9 for 99 Tc/Mo and 99 Tc/Ru, respectively. Spike and recovery tests were conducted for environmental samples; the resulting values showed good agreement with the spike applied., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

RvE1 ( 1 ) is an endogenous lipid mediator with very potent anti-inflammatory activity, which is due to the inhibition of neutrophil chemotaxis and inflammatory cytokine production and the promotion of macrophage phagocytosis. On the basis of the conformational analysis of RvE1, we designed its four cyclopropane congeners ( 2a - d ), in which the conformationally flexible terminal C1-C4 moiety of RvE1 was rigidified by introducing stereoisomeric cyclopropanes. The four congeners and also RvE1 were efficiently synthesized via a common synthetic route. The evaluation of the anti-inflammatory effects of the compounds in mice resulted in the identification of trans -β-CP-RvE1 ( 2d ), which was significantly more active than RvE1, as a potential lead for anti-inflammatory drugs of a novel mechanism of action., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

We synthesized RvE3 and its deoxy derivatives, 17-deoxy-RvE3 and 18-deoxy-RvE3, by a common route via Sonogashira coupling as a key step. The evaluation of their anti-inflammatory activities revealed that 18-deoxy-RvE3 was remarkably more potent than the parent RvE3 and significantly active at a 300 fg dose in mice; additionally, 17-deoxy-RvE3 was significantly less potent than the parent RvE3. For the first time, we found that the 17-hydroxy group of RvE3 is very important for anti-inflammatory activity.

Resolvins (Rvs) are highly potent anti-inflammatory lipid mediators that are chemically and biologically unstable because of their polyunsaturated structures. To address this issue, we designed benzene congeners of RvE2, i.e., o -, m -, and p -BZ-RvE2s, as stable equivalents of RvE2 by replacing the unstable skipped diene moiety with a benzene ring on the basis of computational conformation studies and synthesized these congeners via a short common route through two Stille couplings. o -BZ-RvE2 exhibited more potent anti-inflammatory activity and much higher metabolic stability than RvE2. Thus, o -BZ-RvE2 was identified as a stable equivalent of RvE2, which is useful as a lead for anti-inflammatory drugs with a new mechanism of action as well as a biotool for investigating RvE2-mediated inflammation resolving pathways., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

A dextran-peptide conjugate was developed for magnetic resonance (MR) molecular imaging of pancreatic ductal adenocarcinoma (PDAC) through its overexpressed microenvironment biomarker, extradomain-B fibronectin (EDB-FN). This new agent consists of diamagnetic and biocompatible dextran and a targeting peptide. Dextrans can be directly detected by chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) without the need for radionuclide or metallic labeling. In addition, large molecular weight dextran, dextran 10 (MW ∼ 10 kDa), provides an approximately 50 times higher sensitivity per molecule than a single glucose unit. The potential of this highly biocompatible diamagnetic probe is demonstrated in a murine syngeneic allograft PDAC tumor model. The biocompatibility and sensitivity of this new agent clearly show potential for a path to clinical translation.

Neuroferritinopathy is a rare, adult-onset, dominantly inherited movement disorder caused by mutations in the ferritin gene. A ferritin light-chain variant related to neuroferritinopathy, in which alanine 96 is replaced with threonine (A96T), was expressed in Escherichia coli, purified, and characterized. The circular dichroism, analytical ultracentrifugation, and small-angle X-ray scattering studies have shown that both the subunit structure and the assembly of A96T are the same as those of wild-type human ferritin light chain (HuFTL). The iron-incorporation ability was also comparable to that of HuFTL. Although the structural stability against heat, acid, and denaturant was reduced, the structure was sufficiently stable under physiological conditions. The most remarkable defects observed for A96T were a lower refolding efficiency and a stronger propensity to aggregate. The possible relationship between folding deficiency and disease is discussed.

A conjugate addition of diverse nucleophiles to acylketene acetals derived from 1,8-dihydroxynaphthalene (DHN) is developed for the formation of its 3-oxoalkan-1-one acetals. The initial acylketene acetals are prepared via double oxa-Michael addition of DHN to 1-bromo-1-propyn-3-ones. Carbonucleophiles, including organocopper reagents and active methylene compounds, and heteroatom nucleophiles were introduced under basic conditions. This method is applied for synthesizing spiropreussione A; the proposed structure does not correspond to that of the authentic natural product.

Described herein are syntheses of the naturally occurring polyketides (-)-tetrapetalones A and C and their respective enantiomers. The employed strategy involves initial assembly of a masked N-aryl tetramic acid which is advanced via a highly selective conjugate addition/intramolecular Friedel-Crafts acylation sequence to deliver a key azepine intermediate. Application of recently developed C-H activation chemistry and subsequent Heck cyclization delivers the aglycone framework in an overall 12 steps. Resolution of the aglycone via stereospecific glycosylation with an enantiopure glycosyl donor followed by separation of the derived diastereomers enables further advancement to either (+)- or (-)-tetrapetalones A and C.

Yolk-shell nanostructured photocatalyst which consists of inner core photocatalytic particles and outer silica shell exhibits high photocatalytic efficiency and molecular size selectivity due to the molecular sieving property of the outer shell. Creation of extended porosity in the shell endows it with improved adsorption properties and size selectivity toward targeted reactants. In this study, yolk-shell nanostructured photocatalyst consisting of TiO 2 NPs core and porous silica shell with controllable pore size was fabricated through a facile single-step dual-templating approach utilizing oil-in-water (O/W) microemulsions and amphiphilic protein molecules. Addition of optimum amount of protein (ovalbumin) as a sacrificial template together with O/W microemulsion during the synthesis led to the expansion of average pore size from 2.0 to 3.6 nm, while retaining TiO 2 -encapsulated yolk-shell nanostructures. Photocatalytic degradation tests using gaseous 2-propanol and huge proteins as model substrates clearly revealed that the obtained material (TiO 2 @HSS_pro) showed superior photocatalytic performances with both improved photocatalytic efficiency and molecular size selectivity due to the increased surface area and expanded pore diameter.

Haemophilus influenzae adhesin (Hia) belongs to the trimeric autotransporter family and mediates the adherence of these bacteria to the epithelial cells of host organisms. Hia contains a passenger and a transmembrane domain. The transmembrane domain forms a 12-stranded β-barrel in which four strands are provided by each subunit. The β-barrel has a pore that is traversed by three α-helices. This domain has a unique arginine cluster, in which the side chains of the three arginine residues located at position 1077 (Arg1077) protrude into the pore of the β-barrel. This arrangement seems to be unfavorable for assembly, because of repulsion between the positive charges. In this study, we investigated the in vitro assembly of the Hia transmembrane minimum domain (mHiaTD) and found that the dissociated mHiaTD reassembled in detergent solution. To investigate the role of Arg1077 in trimer assembly, we generated mutant proteins in which Arg1077 was replaced with methionine or lysine. The reassembly kinetics of the mutants was compared with that of the wild-type protein. The methionine mutant showed misassembly, whereas the lysine mutant showed reversible assembly, similar to that observed for the wild-type protein. These results show that electrostatic repulsion between the positive charges of Arg1077 is important for preventing the formation of misassembled oligomers by the mHiaTD in vitro.

TiO 2 nanoparticles (NPs) encapsulated in hollow silica spheres (TiO 2 @HSSs) show a shielding-effect that can insulate photocatalytically active TiO 2 NPs from the surrounding environment and thus prohibit the self-degradation of organic support materials under ultraviolet (UV)-light irradiation. In this study, photocatalytically active papers were fabricated by combining TiO 2 @HSS and cellulose fibers, and their photocatalytic activities and durability under UV-light irradiation were examined. The yolk-shell nanostructured TiO 2 @HSS, which has an ample void space between inner TiO 2 NPs and an outer silica shell, was synthesized using a facile single-step method utilizing an oil-in-water microemulsion as an organic template. The thus-prepared TiO 2 @HSS particles were deposited onto a cellulose paper either by the chemical adhesion process via ionic bonding or by the physical adhesion process using a dual polymer system. The obtained paper containing TiO 2 @HSS particles with high air permeability exhibited a higher photocatalytic activity in the photocatalytic decomposition of volatile organic compounds than unsupported powdery TiO 2 @HSS particles because of the uniform dispersion on the paper with a reticular fiber network. In addition, the paper was hardly damaged under UV-light irradiation, whereas the paper containing naked TiO 2 NPs showed a marked deterioration with a considerably decreased strength, owing to the ability of the silica shell to prevent direct contact between TiO 2 and organic fibers. This study can offer a promising method to fabricate photocatalytically active papers with a photoresistance property available for real air cleaning.

In the gold nanoparticle (Au NP)-loaded CdS film on fluorine-doped tin oxide electrode (Au/CdS/FTO), the localized plasmonic resonance excitation-induced electron injection from Au NP to CdS has been proven by photoelectrochemical measurements. Formation of ZnS thin films between the Au NP and CdS film leads to a drastic increase of the photocurrent under visible-light irradiation (λ > 610 nm) in a 0.1 M NaClO 4 aqueous electrolyte solution due to the electron filtering effect. The photocurrent strongly depends on the thickness of the ZnS film, and the maximum value is obtained at a thickness as thin as 2.1 nm. Furthermore, the ZnS overlayer significantly stabilizes the photocurrent of the CdS/FTO electrode in a polysulfide/sulfide electrolyte solution even under the excitation of CdS (λ > 430 nm). This work presents important information about the design for new plasmonic photocatalysts consisting of plasmonic metal NPs and chalcogenide semiconductors with high conduction band edge.

Aberrant DNA methylation causes major epigenetic changes and has been implicated in cancer following the inactivation of tumor suppressor genes by hypermethylation of promoter CpG islands. Although methylated DNA regions can be randomly demethylated by 5-azacytidine and 5-aza-2'-deoxycytidine, site-specific inhibition of DNA methylation, for example, in the promoter region of a specific gene, has yet to be technically achieved. Hairpin pyrrole (Py)-imidazole (Im) polyamides are small molecules that can be designed to recognize and bind to particular DNA sequences. In this study, we synthesized the hairpin polyamide MLH1_-16 (Py-Im-β-Im-Im-Py-γ-Im-Py-β-Im-Py-Py) to target a CpG site 16 bp upstream of the transcription start site of the human MLH1 gene. MLH1 is known to be frequently silenced by promoter hypermethylation, causing microsatellite instability and a hypermutation phenotype in cancer. We show that MLH1_-16 binds to the target site and that CpG methylation around the binding site is selectively inhibited in vitro. MLH1_non, which does not have a recognition site in the MLH1 promoter, neither binds to the sequence nor inhibits DNA methylation in the region. When MLH1_-16 was used to treat RKO human colorectal cancer cells in a remethylating system involving the MLH1 promoter under hypoxic conditions (1% O 2 ), methylation of the MLH1 promoter was inhibited in the region surrounding the compound binding site. Silencing of the MLH1 expression was also inhibited. Promoter methylation and silencing of MLH1 were not inhibited when MLH1_non was added. These results indicate that Py-Im polyamides can act as sequence-specific antagonists of CpG methylation in living cells., Competing Interests: The authors declare the following competing financial interest(s): As for Inhibition of DNA methylation in living cells, we filed a patent for PIP molecule.

Despite the widespread use of transition-metal catalysts in organic synthesis, transition-metal-catalyzed reactions of organosulfur compounds, which are known as catalyst poisons, have been difficult. In particular, the transition-metal-catalyzed addition of organosulfur compounds to unactivated alkenes remains a challenge. A novel gold-catalyzed hydrothiolation of unactivated alkenes is presented, which proceeds effectively to give the anti-Markovnikov-selective adducts in good yields and in a regioselective manner.

Escherichia coli non-heme-binding ferritin A (EcFtnA) is a spherical cagelike protein that is composed of 24 identical subunits. EcFtnA dissociates into 2-mers under acidic conditions and can reassemble into the native structure when the pH is increased. To understand how electrostatic interactions influence the assembly reaction, the dependence of the process on ionic strength and pH was investigated. The assembly reaction was initiated by stopped-flow mixing of the acid-dissociated EcFtnA solution and high-pH buffer solutions and monitored by time-resolved small-angle X-ray scattering. The rate of assembly increased with increasing ionic strength and decreased with increasing pH from 6 to 8. These dependences were thought to originate from repulsion between assembly units (2-mer in the case of EcFtnA) with the same net charge sign; therefore, to test this assumption, mutants with different net charges (net-charge mutants) were prepared. In buffers with a low ionic strength, the rate of assembly increased with a decreasing net charge. Thus, repulsion between the assembly unit net charges was demonstrated to be an important factor determining the rate of assembly. However, the difference in the assembly rate among net-charge mutants was not significant in buffers with an ionic strength of >0.1. Notably, under such high-ionic strength conditions, the assembly rate increased with an increasing ionic strength, suggesting that local electrostatic interactions are also responsible for the ionic strength dependence of the rate of assembly and are repulsive on average.

The assembly reaction of Escherichia coli ferritin A (EcFtnA) was studied using time-resolved small-angle X-ray scattering (TR-SAXS). EcFtnA forms a cagelike structure that consists of 24 identical subunits and dissociates into dimers at acidic pH. The dimer maintains nativelike secondary and tertiary structures and is able to reassemble into a 24-mer when the pH is increased. The reassembly reaction was induced by pH jump, and reassembly was followed by TR-SAXS. Time-dependent changes in the forward scattering intensity and in the gyration radius suggested the existence of a significant population of intermediate oligomers during the assembly reaction. The initial reaction was a mixture of second- and third-order reactions (formation of tetramers and hexamers) from the protein concentration dependence of the initial velocity. The time-dependent change in the SAXS profile was roughly explained by a simple model in which only tetramers, hexamers, and dodecamers were considered as intermediates.

Ferritin A from Escherichia coli (EcFtnA) is 24-meric protein, which forms spherical cagelike structures called nanocages. The nanocage structure is stabilized by the interface around 4-, 3-, and 2-fold symmetric axes. The subunit structure of EcFtnA comprises a four-helix bundle (helices A-D) and an additional helix E, which forms a 4-fold axis. In this study, we examined the contribution of the interface around three symmetric axes. pH-induced dissociation experiments monitored by analytical ultracentrifugation and small-angle X-ray scattering showed that the dimer related by 2-fold symmetry is the most stable unit. Mutations located near the 3-fold axis revealed that the contribution of each interaction was small. A mutant lacking helix E at the 4-fold axis formed a nanocage, suggesting that helix E is not essential for nanocage formation. Further truncation of the C-terminus of helix D abrogated the formation of the nanocage, suggesting that a few residues located at the C-terminus of helix D are critical for this process. These properties are similar to those known for mammalian ferritins and seem to be common principles for nanocage formation. The difference between EcFtnA and mammalian ferritins was that helix E-truncated EcFtnA maintained an iron-incorporating ability, whereas mammalian mutants lost it.

We demonstrate two types of inversion of a helical preference upon the 1:1 complexation of a dynamic figure eight molecule with a guest molecule through the controlled transmission of point chirality. We designed a series of macrocycles that prefer a nonplanar conformation with figure eight chirality. These macrocycles are composed of a chirality-transferring unit (terephthalamide) and a structure-modifying unit (two o-phenylene rings spaced with a varying number of triple bonds). The former unit provides a binding site for capturing a guest molecule through the formation of hydrogen bonds. The attachment of chiral auxiliaries to the former unit induces a helical preference for a particular sense through the intramolecular transmission of point chirality. For relatively small-sized macrocycles, the preferred sense was reversed upon complexation with an achiral guest. Contrary preferences before and after complexation were both seen for chiral auxiliaries associated with a figure eight host through two-way intramolecular transmission of the single chiral source. Alternatively, the helical preference induced in relatively large-sized macrocycles was reversed only when a figure eight host formed a 1:1 complex with a particular enantiomeric guest through the supramolecular transmission of point chirality in the guest. This stereospecific inversion of a helical preference is rare.

In the scaling down of electronic devices, functional oxides with strongly correlated electron system provide advantages to conventional semiconductors, namely, huge switching owing to their phase transition and high carrier density, which guarantee their rich functionalities even at the 10 nm scale. However, understanding how their functionalities behave at a scale of 10 nm order is still a challenging issue. Here, we report the construction of the well-defined (La,Pr,Ca)MnO3 epitaxial oxide nanowall wire by combination of nanolithography and subsequent thin-film growth, which allows the direct investigation of its insulator-metal transition (IMT) at the single domain scale. We show that the width of a (La,Pr,Ca)MnO3 nanowall sample can be reduced to 50 nm, which is smaller than the observed 70-200 nm-size electronic domains, and that a single electronic nanodomain in (La,Pr,Ca)MnO3 exhibited an intrinsic first-order IMT with an unusually steep single-step change in its magnetoresistance and temperature-induced resistance due to the domains arrangement in series. A simple model of the first-order transition for single electric domains satisfactorily illustrates the IMT behavior from macroscale down to the nanoscale.

Nanosilver with closely controlled average particle diameter (7-30 nm) immobilized on nanosilica is prepared and characterized by X-ray diffraction, N2 adsorption, and transmission electron microscopy. The presence of Ag2O on the as-prepared nanosilver surface is confirmed by UV-vis spectroscopy and quantified by thermogravimetric analysis and mass spectrometry. The release of Ag(+) ions in deionized water is monitored electrochemically and traced quantitatively to the dissolution of a preexisting Ag2O monolayer on the nanosilver surface. During this dissolution, the pH of the host solution rapidly increases, suppressing dissolution of the remaining metallic Ag. When, however, a nanosilver suspension is exposed to a CO2-containing atmosphere, like ambient air during its storage or usage, then CO2 is absorbed by the host solution decreasing its pH and contributing to metallic Ag dissolution and further leaching of Ag(+) ions. So the release of Ag(+) ions from the above closely sized nanosilver solutions in the absence and presence of CO2 as well as under synthetic air containing 200-1800 ppm of CO2 is investigated along with the solution pH and related to the antibacterial activity of nanosilver.

The planar and stereostructures of JBIR-108 isolated from Streptomyces gramineus IR087Pi-4 were determined partly by spectral analysis, and these structural assignments were confirmed and completed by the total synthesis of both 1-epimers. The key stereocenters in JBIR-108 were constructed via a Corey-Bakshi-Shibata (CBS) reduction (C-1), vinylogous Mukaiyama aldol reaction (C-7), and Brown crotylation (C-14 and C-15). Although it was difficult to determine the stereochemistries at the C-1 and C-7 positions in the natural product using the modified Mosher's method, the synthesis of two possible C-1 diastereomers enabled the identification of the configurations at the hitherto unknown stereocenters.

Artificial cells, particularly cell-sized liposomes, serve as tools to improve our understanding of the physiological conditions of living cells. However, such artificial cells typically contain a more dilute solution of biomacromolecules than that found in living cells (300 mg mL(-1)). Here, we reconstituted the intracellular biomacromolecular conditions in liposomes using hyperosmotic pressure. Liposomes encapsulating 80 mg mL(-1) of macromolecules of BSA or a protein mixture extracted from Escherichia coli were immersed in hypertonic sucrose. The concentration of macromolecules in BSA-containing liposomes was increased in proportion to the initial osmotic pressure ratio between internal and external media. On the other hand, the concentration of the protein mixture in liposomes could be saturated to reach the physiological concentration of macromolecules in cells. Furthermore, membrane transformation after the hypertonic treatment differed between BSA- and protein mixture-containing liposomes. These results strongly suggested that the crowded environment in cells is different from that found in typical single-component systems.

A foldable cyclic oligomer 1 consisting of three terephthalamide units spaced with a 3-fold o-phenylene unit presented a dynamic pair of enantiomeric forms through molecular folding, to which the external chirality on a ditopic guest [(S,S)-2 or (R,R)-2] was supramolecularly transferred to prefer a particular sense of dynamic helicity [(M,M)-/(P,P)-1 and (M,M,P)-/(P,P,M)-1]. In the macrocycle, the terephthalamide units acted as exotopic binding sites to fold into helical forms upon complexation. The internal chirality associated with a host [(R,R,R,R,R,R)-1b] had no preference in a helical sense in the absence of a guest. Instead, the internal chirality was responsible for the signal modulation that it was cooperatively or competitively transferred in response to the external chirality on a guest (S,S)-2 or (R,R)-2. During the diastereomeric complexation, a particular sense of dynamic helicity was favored due to cooperative transmission of chirality when the helical preference was matched between the host and guest. Alternatively, the host complexed with an antipodal guest underwent a drastic change in conformation upon a change in temperature.

The direct and reversible transformation of matter between the solid and liquid phases by light at constant temperature is of great interest because of its potential applications in various manufacturing settings. We report a simple molecular design strategy for the phase transitions: azobenzenes having para-dialkoxy groups with a methyl group at the meta-position. The photolithography processes were demonstrated using the azobenzene as a photoresist in a single process combining development and etching of a copper substrate.

The structure of the prespore-cell-promoting factor from Dictyostelium discoideum was determined to be 2-hydroxy-5-methyl-6-pentylbenzoquinone. The synthetic compound has prespore-cell-promoting activity similar to the natural one, with half-maximal induction at a concentration as low as 40 pM. It was also found that the factor induces aggregation in an aggregation-deficient mutant of a related species, Polysphodilium violaceum. Both these activities are sensitive to positional isomerism with the 6-methyl-5-pentyl isomer showing no detectable activity.

Many studies have shown that during the early stages of the folding of a protein, chain collapse and secondary structure formation lead to a partially folded intermediate. Thus, direct observation of these early folding events is crucial if we are to understand protein-folding mechanisms. Notably, these events usually manifest as the initial unresolvable signals, denoted the burst phase, when monitored during conventional mixing experiments. However, folding events can be substantially slowed by first trapping a protein within a silica gel with a large water content, in which the trapped native state retains its solution conformation. In this study, we monitored the early folding events involving secondary structure formation of five globular proteins, horse heart cytochrome c, equine β-lactoglobulin, human tear lipocalin, bovine α-lactalbumin, and hen egg lysozyme, in silica gels containing 80% (w/w) water by CD spectroscopy. The folding rates decreased for each of the proteins, which allowed for direct observation of the initial folding transitions, equivalent to the solution burst phase. The formation of each initial intermediate state exhibited single exponential kinetics and Arrhenius activation energies of 14-31 kJ/mol.

We have found that an impurity partitioning takes place during growth of colloidal crystals, which was recognized by the fact that the impurity concentration in the solid (CS) was different from that in the initial solution (C0). The effective partition coefficient k(eff) (=CS/C0) was investigated for pure polystyrene and polystyrene dyed with fluorescent particles by changing the ratio of particle diameters d(imp)/d(cryst) and growth rate V. At each size ratio for the polystyrene impurity, k(eff) was less than unity and increased to unity with increasing V, whereas at a given growth rate, k(eff) increased to unity as d(imp)/d(cryst) approached unity. These results were consistent with the solute behavior analyzed using the Burton, Prim, and Slichter (BPS) model. The obtained k0, equilibrium partition coefficient, from a BPS plot increased as d(imp)/d(cryst) approached unity. In contrast, while the fluorescent particles also followed the BPS model, they showed higher k0 values than those of the same size of polystyrene particles. A k0 value greater than unity was obtained for impurities that were similar in size to the host particle. This behavior is attributed to the positive free energy of fusion associated with the incorporation of the fluorescent particles into the host matrix. Such positive free energy of fusion implies the presence of the enthalpy associated with interaction between particles.

A novel 2',3'-dihydroxy-p-terphenyl derivative, thelephantin O (TO), which has cancer-selective cytotoxicity, was isolated. This study investigated the underlying basis of the cytotoxicity of 2',3'-dihydroxy-p-terphenyl compounds in view of their ability to chelate metal ions. FeCl(2) significantly reduced TO-induced cytotoxicity, whereas several other salts of transition metals and alkaline-earth metals did not. A structure-activity relationship study using newly synthesized p-terphenyl derivatives revealed that o-dihydroxy substitution of the central benzene ring was necessary for both the cytotoxicity and Fe(2+) chelation of the compounds. Real-time PCR array and cell cycle analysis revealed that the TO-induced cytotoxicity was attributed to cell cycle arrest at the G1 phase via well-known cell cycle-mediated genes. The TO-induced changes in the cell cycle and gene expression were completely reversed by the addition of FeCl(2). Thus, it was concluded that Fe(2+) chelation occurs upstream in the pivotal pathway of 2',3'-dihydroxy-p-terphenyl-induced inhibition of cancer cell proliferation.

The Fer-CIP4 homology-BAR (F-BAR) domain, which was identified as a biological membrane-deforming module, has been reported to transform lipid bilayer membranes into tubules. However, details of the tubulation process, the mechanism, and the properties of the generated tubules remain unknown. Here, we successfully monitored the entire process of tubulation and the behavior of elongated tubules caused by four different F-BAR domain family proteins (FBP17, CIP4, PSTPIP1, and Pacsin2) using direct real-time imaging of giant unilamellar liposomes with dark-field optical microscopy. FBP17 and CIP4 develop many protrusions simultaneously over the entire surface of individual liposomes, whereas PSTPIP1 and Pacsin2 develop only a few protrusions from a narrow restricted part of the surface of individual liposomes. Tubules formed by FBP17 or CIP4 have higher bending rigidities than those formed by PSTPIP1 or Pacsin2. The results provide striking evidence that these four F-BAR domain family proteins should be classified into two groups: one group of FBP17 and CIP4 and another group of PSTPIP1 and Pacsin2. This classification is consistent with the phylogenetic proximity among these proteins and suggests that the nature of the respective tubulation is associated with biological function. These findings aid in the quantitative assessment with respect to manipulating the morphology of lipid bilayers using membrane-deforming proteins.

Ion transportation via the chloride ion pump protein pharaonis halorhodopsin (pHR) occurs through the sequential formation of several intermediates during a photocyclic reaction. Although the structural details of each intermediate state have been studied, the role of water molecules in the translocation of chloride ions inside of the protein at physiological temperatures remains unclear. To analyze the structural dynamics of water inside of the protein, we performed time-resolved Fourier transform infrared (FTIR) spectroscopy under H2O or H2(18)O hydration and successfully assigned water O-H stretching bands. We found that a dangling water band at 3626 cm(-1) in pHR disappears in the L1 and L2 states. On the other hand, relatively intense positive bands at 3605 and 3608 cm(-1) emerged upon the formation of the X(N) and O states, respectively, suggesting that the chloride transportation is accompanied by dynamic rearrangement of the hydrogen-bonding network of the internal water molecules in pHR.

The first total synthesis of natural, unsymmetrical 2',3'-diacyloxy-p-terphenyls, thelephantin O (1) and terrestrins C and D (2 and 3, respectively), was achieved via a practical route which was also applicable to the synthesis of the symmetrical diesters vialinin A/terrestrin A (4) and terrestrin B (5). Compounds 1-5 exhibited cytotoxicity against cancer cells (HepG2 and Caco2) with IC(50) values of 13.6-26.7 μmol/L.

Cationic iron(III) porphyrin was found to be an efficient catalyst for the highly chemoselective hetero-Diels-Alder-type reaction of aldehydes with 1,3-dienes. The catalyzed process did not require the use of electron-deficient aldehydes such as glyoxylic acid derivatives or activated electron-rich 1,3-dienes such as Danishefsky's diene and Rawal's diene. The high functional group tolerance and robustness of the catalyst were demonstrated. Further, the potential utility of the catalyst was demonstrated by performing the cycloaddition in the presence of water and by carrying out cycloaddition of an unactivated ketone such as cyclohexanone with a diene.

Equine β-lactoglobulin (ELG) assumes non-native helices during refolding and in partially folded states. Previously, circular dichroism (CD) combined with site-directed mutagenesis identified helical regions in the acid- and cold-denatured states of ELG. It is also known that a fragment of ELG, CHIBL (residues 88-142), has a structure similar to that of the cold-denatured state. For the study reported herein, the structure of a shorter fragment, CHIBLΔF (residues 97-142), was investigated by CD and nuclear magnetic resonance spectroscopy. The secondary chemical shifts clearly showed that non-native α-helices are present in two different regions, residues 98-107 and 114-135, and are connected by a native disulfide bond. The CD spectra of two peptides that correspond to the helical regions are characterized by weak helical signatures, and the sum of their CD spectra is nearly the same as the spectrum of disulfide-reduced CHIBLΔF. Therefore, the non-native helices are stabilized by the disulfide, and non-native helix formation may occur only during the refolding of the disulfide-intact protein. Supporting this conclusion is the observation that tear lipocalin, a homologue of ELG that lacks the disulfide, does not form non-native helices during folding.

To propose new molecular markers for tire-wear emissions, four dihydroresin acids, that is, 8-isopimaren-18-oic acid (I), 8-pimaren-18-oic acid (II), 13β(H)-abieten-18-oic acid (III), and 13α(H)-abiet-8-en-18-oic acid (IV), were identified and investigated for source specificities, distributions, and environmental stabilities. The absence of I-IV in natural sources and the linear correlations between dihydroresin acids with different skeletons in tires and in environmental samples demonstrated that I-IV are specific markers for synthetic rubbers. The ratio of III + IV to the sum of III + IV plus abietic acid showed the resin acids distribution between different environmental compartments receiving contributions from traffic and natural sources. The physicochemical properties and results of photolysis experiments suggested that I-IV can set lower limits for tire-wear contributions to environmental loads of particulate matter (PM) and polycyclic aromatic hydrocarbons with molecular weight ≥202. By comparing III + IV concentrations or (III+IV)/pyrene or (III+IV)/benzo[a]pyrene ratios in tires and those in environmental matrices, the contributions of tire-wear emissions to PM, pyrene, and benzo[a]pyrene were estimated to be 0.68 ± 0.54%, 6.9 ± 4.8%, and 0.37 ± 0.18% in roadside PM and 0.83 ± 0.21%, 0.88 ± 0.52%, and 0.08 ± 0.06% in rooftop PM.

Thelephora aurantiotincta is an edible mushroom belonging to the genus Thelephora; it grows in symbiosis with pine trees. Recently, phytochemical investigations have revealed that the genus Thelephora is an abundant source of p-terphenyl derivatives. However, their bioactivity has not yet been well characterized. In screening for natural materials with anticancer activity, a T. aurantiotincta ethanol extract (TAE) was found to decrease cell viability in human hepatocellular carcinoma cells (HepG2). In this study, a new p-terphenyl derivative, thelephantin O, and a known compound, vialinin A, were isolated as the principal bioactive components of TAE. These compounds decreased cell viability in HepG2 and human colonic carcinoma cells (Caco2), but not in noncancerous human hepatocytes. This is the first report of the isolation from T. aurantiotincta of selective cytotoxic agents against cancer cells.

The effect of an external ac electric field on the nucleation rate of hen egg white lysozyme crystals increased with an increase in the concentration of the precipitant used, which enabled the design of an electric double layer (EDL) formed at the inner surface of the drop in the oil. This is attributed to the thickness of the EDL controlled by the ionic strength of the precipitant used. Control of the EDL formed at the interface between the two phases is important to establishing this novel technique for the crystallization of proteins under the application of an external ac electric field., (© 2011 American Chemical Society)

The decarbonylative cycloadditions of phthalimides with 1,3-dienes were performed by using nickel catalyst. The reactions afford 3-vinyldihydroisoquinolones regioselectively with respect to both 1,3-dienes and phthalimides.

Bipyridine derivatives (bpys) with various number and length of peripheral alkyl chains (with carbon numbers of n = 11-17) were synthesized, and their self-assembled monolayers were observed by scanning tunneling microscopy (STM) at a 1-phenyloctane/highly oriented pyrolytic graphite (HOPG) interface. The effects of the number, the substitution position, and the length of alkyl chains on the two-dimensional structures were systematically studied. Bpys substituted by a single alkyl chain in the p-position on each side adopted an almost linear form with zigzag-type alignment of the pi-conjugated unit, whereas, in the case of m-substitution, the bpys showed Z-shaped morphology with interdigitated alkyl chains. In both cases, no odd-even alkyl chain length effects were observed. The bpys with double alkyl chains at m- and p-positions displayed odd-even alkyl chain effects, suggesting that the formation of two-dimensional structure is dominated by the interactions between alkyl chains. Bpys with triple alkyl chains at o-, m-, and p-positions also showed odd-even alkyl chain effects, but only for the higher number of carbon atoms in the alkyl chain unit (n = 14-17). These results indicate that concerted intermolecular interactions of the alkyl chain unit introduce the odd-even chain length effect on the self-assembled two-dimensional structure. After coordination of PdCl(2), odd-even effects were quenched, and bpys were converged into the same lamellar structure, in which the molecules are almost linear. All the structural differences due to the odd-even alkyl chain length effect were explained in terms of intermolecular and molecule-substrate interactions.