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P-Stereogenic phosphinamides represent important structural elements in chiral organocatalysts and bioactive compounds. Herein, we report Pd(II)-catalyzed enantioselective C–H alkynylation using cheap commercially available l-pyroglutamic acid as a chiral ligand. A range of structurally diverse P-stereogenic phosphinamides was prepared in good yields with high enantioselectivities via desymmetrization and kinetic resolution. A tailor-made congested directing group, N-ethyl-N-(3-methylpyridin-2-yl)amino, was crucial for the reactivity.

Development of hydrogel-based actuators with programmable deformation is an important topic that arouses much attention in fundamental and applied research. Most of these actuators are nonbiodegradable or work under nonphysiological conditions. Herein, a temperature-responsive and biodegradable gelatin methacryloyl (GelMA)–poly(N-isopropylacrylamide) hydrogel (i.e., GN hydrogel) network was explored as the active layer of a bilayer actuator. Small-angle X-ray scattering (SAXS) revealed that the GN hydrogel formed a mesoglobular structure (∼230 Å) upon a thermally induced phase transition. Rheological data supported that the GN hydrogel possessed 3D printability and tunable mechanical properties. A bilayer hydrogel actuator composed of active GN and passive GelMA layers was optimized by varying the layer thickness and compositions to achieve large, reproducible, and anisotropic bending with a curvature of ∼5.5 cm–1. Different patterns of the active layer were designed for actuation in programmable control. The 3D printed GN hydrogel constructs showed significant volume reduction (∼25–60% depending on construct design) at 37 °C with the resolution enhanced by the thermo-triggered actuation, while they were able to fully reswell at room temperature. A more intricate 3D printed butterfly actuator demonstrated the ability to mimic the wing movement through thermoresponsiveness. Furthermore, myoblasts laden in the GN hydrogel exhibited significant proliferation of ∼376% in 14 days. This study provides a new fabrication approach for developing biomimetic devices, artificial muscles, and soft robotics for biomedical applications.

Light-harvesting 2 (LH2) antenna complexes augment the collection of solar energy in many phototrophic bacteria. Despite its frequent role as a model for such complexes, there has been no three-dimensional (3D) structure available for the LH2 from the purple phototroph Rhodobacter sphaeroides. We used cryo-electron microscopy (cryo-EM) to determine the 2.1 Å resolution structure of this LH2 antenna, which is a cylindrical assembly of nine αβ heterodimer subunits, each of which binds three bacteriochlorophyll a(BChl) molecules and one carotenoid. The high resolution of this structure reveals all of the interpigment and pigment–protein interactions that promote the assembly and energy-transfer properties of this complex. Near the cytoplasmic face of the complex there is a ring of nine BChls, which absorb maximally at 800 nm and are designated as B800; each B800 is coordinated by the N-terminal carboxymethionine of LH2-α, part of a network of interactions with nearby residues on both LH2-α and LH2-β and with the carotenoid. Nine carotenoids, which are spheroidene in the strain we analyzed, snake through the complex, traversing the membrane and interacting with a ring of 18 BChls situated toward the periplasmic side of the complex. Hydrogen bonds with C-terminal aromatic residues modify the absorption of these pigments, which are red-shifted to 850 nm. Overlaps between the macrocycles of the B850 BChls ensure rapid transfer of excitation energy around this ring of pigments, which act as the donors of energy to neighboring LH2 and reaction center light-harvesting 1 (RC–LH1) complexes.

A Pd(II)-catalyzed enantioselective C–H alkynylation of 2-(arylsulfinyl)pyridines via kinetic resolution using cheap and commercially available l-pGlu-OH as a chiral ligand is reported. A wide range of 2-(arylsulfinyl)pyridines were compatible with this protocol, giving the alkynylation products and recovered sulfoxides in high yields with high enantioselectivities (up to 99% ee). Furthermore, the enantioenriched products can be easily transformed to several other types of chiral sulfoxide scaffolds with the retention of enantiopurity.

The cytochrome b6f(cytb6f) complex has a central role in oxygenic photosynthesis, linking electron transfer between photosystems I and II and converting solar energy into a transmembrane proton gradient for ATP synthesis1–3. Electron transfer within cytb6foccurs via the quinol (Q) cycle, which catalyses the oxidation of plastoquinol (PQH2) and the reduction of both plastocyanin (PC) and plastoquinone (PQ) at two separate sites via electron bifurcation2. In higher plants, cytb6falso acts as a redox-sensing hub, pivotal to the regulation of light harvesting and cyclic electron transfer that protect against metabolic and environmental stresses3. Here we present a 3.6 Å resolution cryo-electron microscopy (cryo-EM) structure of the dimeric cytb6fcomplex from spinach, which reveals the structural basis for operation of the Q cycle and its redox-sensing function. The complex contains up to three natively bound PQ molecules. The first, PQ1, is located in one cytb6fmonomer near the PQ oxidation site (Qp) adjacent to haem bpand chlorophyll a. Two conformations of the chlorophyll aphytyl tail were resolved, one that prevents access to the Qpsite and another that permits it, supporting a gating function for the chlorophyll ainvolved in redox sensing. PQ2 straddles the intermonomer cavity, partially obstructing the PQ reduction site (Qn) on the PQ1 side and committing the electron transfer network to turnover at the occupied Qnsite in the neighbouring monomer. A conformational switch involving the haem cnpropionate promotes two-electron, two-proton reduction at the Qnsite and avoids formation of the reactive intermediate semiquinone. The location of a tentatively assigned third PQ molecule is consistent with a transition between the Qpand Qnsites in opposite monomers during the Q cycle. The spinach cytb6fstructure therefore provides new insights into how the complex fulfils its catalytic and regulatory roles in photosynthesis.

The light-harvesting 1–reaction centre (LH1–RC) complex is a key functional component of bacterial photosynthesis. Here we present a 2.9 Å resolution cryo-electron microscopy structure of the bacteriochlorophyll b-based LH1–RC complex from Blastochloris viridisthat reveals the structural basis for absorption of infrared light and the molecular mechanism of quinone migration across the LH1 complex. The triple-ring LH1 complex comprises a circular array of 17 β-polypeptides sandwiched between 17 α- and 16 γ-polypeptides. Tight packing of the γ-apoproteins between β-polypeptides collectively interlocks and stabilizes the LH1 structure; this, together with the short Mg–Mg distances of bacteriochlorophyll bpairs, contributes to the large redshift of bacteriochlorophyll babsorption. The ‘missing’ 17th γ-polypeptide creates a pore in the LH1 ring, and an adjacent binding pocket provides a folding template for a quinone, Q P, which adopts a compact, export-ready conformation before passage through the pore and eventual diffusion to the cytochrome bc1complex. A cryo-electron microscopy structure of the light-harvesting–reaction centre (LH1–RC) complex of the photosynthetic bacterium Blastochloris viridis suggests factors that underlie the large redshift in the absorption spectrum of bacteriochlorophyll in the complex and that promote quinone–quinol translocation across the LH1 ring.

The function of bioenergetic membranes is strongly influenced by the spatial arrangement of their constituent membrane proteins. Atomic force microscopy (AFM) can be used to probe protein organization at high resolution, allowing individual proteins to be identified. However, previous AFM studies of biological membranes have typically required that curved membranes are ruptured and flattened during sample preparation, with the possibility of disruption of the native protein arrangement or loss of proteins. Imaging native, curved membranes requires minimal tip–sample interaction in both lateral and vertical directions. Here, long-range tip–sample interactions are reduced by optimizing the imaging buffer. Tapping mode AFM with high-resonance-frequency small and soft cantilevers, in combination with a high-speed AFM, reduces the forces due to feedback error and enables application of an average imaging force of tens of piconewtons. Using this approach, we have imaged the membrane organization of intact vesicular bacterial photosynthetic “organelles”, chromatophores. Despite the highly curved nature of the chromatophore membrane and lack of direct support, the resolution was sufficient to identify the photosystem complexes and quantify their arrangement in the native state. Successive imaging showed the proteins remain surprisingly static, with minimal rotation or translation over several-minute time scales. High-order assemblies of RC-LH1-PufX complexes are observed, and intact ATPases are successfully imaged. The methods developed here are likely to be applicable to a broad range of protein-rich vesicles or curved membrane systems, which are an almost ubiquitous feature of native organelles.

When outdoor air flowing through the tailrace tunnel, it will be handled and its thermodynamic conditions will change under the differences of temperature and water vapor pressure between air and water surface, air and tunnel wall. Utilizing the handled air for space cooling in hydropower station is an energy saving, environmental protection and renewable application of natural cold source. In this paper, a detailed quasi-three-dimensional mathematical model of heat and moisture transfer of tailrace tunnel ventilating was developed and validated against the field test data from Yingxiuwan hydropower station, and the validation shows that the model predicts the test results very well. The model can be used to predict the heat and moisture performance of tailrace tunnel ventilating system.

In the photosynthetic purple bacterium Rhodobacter(Rba.) sphaeroides, light is absorbed by membrane-bound light-harvesting (LH) proteins LH1 and LH2. LH1 directly surrounds the reaction center (RC) and, together with PufX, forms a dimeric (RC-LH1-PufX)2protein complex. In LH2-deficient Rba. sphaeroidesmutants, RC-LH1-PufX dimers aggregate into tubular vesicles with a radius of ∼250–550 Å, making RC-LH1-PufX one of the few integral membrane proteins known to actively induce membrane curvature. Recently, a three-dimensional electron microscopy density map showed that the Rba. sphaeroidesRC-LH1-PufX dimer exhibits a prominent bend at its dimerizing interface. To investigate the curvature properties of this highly bent protein, we employed molecular dynamics simulations to fit an all-atom structural model of the RC-LH1-PufX dimer within the electron microscopy density map. The simulations reveal how the dimer produces a membrane with high local curvature, even though the location of PufX cannot yet be determined uniquely. The resulting membrane curvature agrees well with the size of RC-LH1-PufX tubular vesicles, and demonstrates how the local curvature properties of the RC-LH1-PufX dimer propagate to form the observed long-range organization of the Rba. sphaeroidestubular vesicles.

A mathematical model for an ultra-thin catalyst layer in PEFCs is introduced. It utilizes Nernst-Planck and Poisson equations. Calculated polarization curves are shown to compare favourably with published experimental data for ultra-thin catalyst layers. Aspects of current conversion, reactant, current distribution, and catalyst utilization are explored. The effect of catalyst layers thickness on the Pt utilization is discussed. This study gives us a better understanding of transport and reaction at the mesoscopic scale and it furnishes the directions for optimization of this type of catalyst layer.

Five carotenoids existing in the purple bacterium of Rhodobium marinum, lycopene, anhydrorhodovibrin, spirilloxanthin, rhodopin, and rhodovibrin, were isolated and purified. Their configurations in the chromophore region and conformations of the terminal part were determined by 1D, 2D 1H and 13C NMR spectroscopy. The semiempirical quantum chemical calculation AM1 was subsequently performed using the rough 3-D structures established by NOE correlations as an initial input. The final optimized structures are coincident with 1H-1H NOE correlations and match with the X-ray crystallographic data of carotenoids. The calculation results show that chemically symmetrical carotenoids have a Cipoint group. The Cipoint group of molecules was destroyed by asymmetrical terminal part although the polyene chain still keeps it roughly. The polyene region of investigated carotenoids are in all-transwith slightly twisted in-plane and slight out-plane forming s-shape carbon backbone due to the spatial interaction of the methyl groups. Terminal parts, on the other hand, have several stable conformers due to the freely rotatable single bonds, but they prefer to take extended conformations.

Molecular arrangement of two kinds of Langmuir–Blodgett monolayers composed of poly(N-dodecylacrylamide) and N-octadecylacrylamide were characterized with the atomic force microscope (AFM). The dodecyl side chains in the polymer Langmuir–Blodgett monolayer were observed as random molecular arrangement. In contrast, alkyl chains in N-octadecylacrylamide monomer Langmuir–Blodgett film were highly ordered to form two dimensional crystals. The X-ray diffraction patterns of the monomer and polymer Langmuir–Blodgett films were consistent with the AFM observation. The polymer Langmuir–Blodgett monolayer was not destroyed by AFM tip scanned in the contact mode, indicating that the monolayer is mechanically appreciably stable.

AbstractThe synthesis, characterization and structure of a trinitratotri(N-butylcaprolactam)samar-ium (III) complex (1) is reported. The Sm (III) ion is coordinated by nine oxygen atoms, three from NBCLM (N-butylcaprolactam) ligands, which are monodentates, and six from three bidentate nitrate groups. The geometry around the Sm (III) ion is a distorted tricapped trigonal prism. Spectroscopic and thermal decomposition data for 1are reported. Magnetic susceptibilities of 1were measured (80–300 K) and non-linear temperature dependence of magnetic susceptibility and effective magnetic moments were found. The effective moment is 1.8 B. M. at room temperature.

The 1-aza-15-crown 5-ether functional group can be incorporated into polymer Langmuir-Blodgett (LB) films as a comonomer of N-dodecylacrylamide. The surface pressure-area isotherms of the copolymers indicated the formation of the stable condensed monolayers on the air-water interface. The copolymer monolayers could be transferred onto solid substrates by the LB technique (Y-type deposition). The result of voltammetric measurement indicated that the functionalized electrodes covered with copolymer monolayers could collect the Ag+ by soaking them in the AgNO3 aqueous solution.

Optically active polymethacrylates 6and 8, which have pendant axially dissymmetric 1,1′-binaphthalene moiety, were synthesized by radical polymerization of (S)-2-methacryloyloxy- and (S)-2-(3-methacryloyloxypropoxy)-2′-methoxy-1,1′-binaphthalene, respectively. Specific rotation and CD spectrum of 6are rather different from those of the model compound 2-(2,2-dimethylpropanoyloxy)-2′-methoxy-1,1′-binaphthalene (7), while the chiroptical properties of 8are almost the same as those of the corresponding model compound. The difference of the chiroptical properties between 6and 7was attributed to the difference of the dihedral angles between the naphthalene planes of the 1,1′-binaphthalene skeleton. The polymethacrylates 6and 8were coated on a spherical silica gel to give HPLC chiral stationary phases (CSP-6and CSP-8). These CSPs differentiated several enantiomeric 1-aryl-1-alkanols and 1,2-diols as the 3,5-dinitrophenylcarbamates, CSP-8showing better resolution than CSP-6. Furthermore, (S)-2-(5-carboxypentyloxy)-2′-methoxy-1,1′-binaphthalene, a model compound of 8, was prepared and covalently bonded to an aminopropylsilanized silica gel to afford CSP-16, which also resolved these racemates. Thus, the chiral discriminating ability of the polymethacrylate 8would be based not on the secondary and/or higher-ordered structure, but mainly on the interaction between the individual 1,1′-binaphthalene units of 8and the racemates.

Ru(II)-catalyzed enantioselective C–H functionalization involving an enantiodetermining C–H cleavage step remains undeveloped. Here we describe a Ru(II)-catalyzed enantioselective C–H activation/annulation of sulfoximines with α-carbonyl sulfoxonium ylides using a novel class of chiral binaphthyl monocarboxylic acids as chiral ligands, which can be easily and modularly prepared from 1,1′-binaphthyl-2,2′-dicarboxylic acid. A broad range of sulfur-stereogenic sulfoximines were prepared in high yields with excellent enantioselectivities (up to 99% yield and 99% ee) via desymmetrization, kinetic resolution, and parallel kinetic resolution. Furthermore, the resolution products can be easily transformed to chiral sulfoxides and key intermediates for kinase inhibitors.

Self-assembled monolayers of stearic acid, (R,S) and (S)-16-methyloctadecanoic acid ion-paired with 4,4'-bipyridine have been observed on a solution–graphite interface by a scanning tunneling microscope (STM) and the observed macro-scale molecular patterns have been interpreted in terms of absolute chirality of the constituent molecule.

Self-assembled monolayer of Schiff base ligand, N-octadecylsalicylaldimine (C18Sal) has been observed by scanning tunneling microscope on the solution–graphite interface and the molecular geometry has been assigned. The molecular pattern of the Schiff base immediately changed upon addition of Cu(II) associated with in situcomplexation and formation of a new molecular framework.

Self-assembled monolayers of the gelling agent, 12-hydroxyoctadecanoic acid and its 4,4′-bipyridinium salt have been observed on the solution graphite interface using scanning tunnelling microscopy (STM) and the molecular patterns are discussed wth respect to the intermolecular hydrogen bond network.

Self-assembled monolayers of N-octadecylbenzamide (ODB) and N-8-quinolyloctadecanamide (ODQ) have been observed on the solution-solid interface by scanning tunneling microscope (STM). ODB molecules form stripe shaped lamella structure whereas ODQ gave a mosaic pattern in which four molecular sets are interlocked alternately like jigsaw pieces.

The STM observation of self-assembled N-octadecylacrylamide (ODA) and N-octadecylcinnamoylamide (ODC) on a graphite substrate clarified the head to tail alignment of the molecules and s-trans geometry of the alkene double bond and carbonyl group.

Chiral 1,2-dihydroxyoctadecane (C16H33CH(OH)CH2OH) self-assembled on graphite surface was observed by STM and the molecular patterns obtained were interpreted by homochiral association of constituent molecules at hydroxyl groups.