New porphyrin-based metal-organic framework with high porosity: 2-D infinite 22.2-A square-grid coordination network

A new 2-D coordination network with 22.2-A square-grid coordination networks was prepared from a dicopper(II) tetraacetate [Cu2(AcO)4] as a linear linker motif and 5,10,15,20-tetra-4-pyridyl-21H,23H-porphine (H2TPyP) as a four-connected vertex, forming a regular high-porous structure. The characterization by N2 adsorption indicated that this coordination network has uniform micropores and gas adsorption cavities.     

Structure and magnetism of a new 2-D trinuclear Mn(II) polymer

A new complex, {[Mn₃(oba)₂(IP)₂(CH₃COO)₂]·H₂O}_n (1) (H₂oba?=?4,4′-oxybis(benzoic acid), IP?=?1-H-imidazo[4,5-f][1,10]-phenanthroline), has been synthesized and structurally characterized by single-crystal diffraction analysis. The structural determination revealed that 1 has a 2-D grid motif, which can be further linked into a 3-D porous network via packing interactions. The magnetic properties of 1 are discussed.     

Synthesis, Structure and Fluorescent Pr.operty of a Novel 2-D Sheet Inorganicorganic Hybrid Cadmium Polymer [CdBr2（bpdo）]n

A novel 2-D sheet inorganic-organic hybrid cadmium polymer,[CdBr2(bpdo)]n (bpdo=N,N'-O,O-4,4'-bipyridine) has been hydrothermally synthesized and characterized by elemental analysis,IR and single-crystal X-ray diffraction. The crystal crystallizes in monoclinic,space group C2/c,with a=16.336(3),b=3.9904(5),c=18.479(3),β=91.640(6)°,Mr= 460.40,V=1204.1(3)3,Z=4,Dc=2.540 g/cm3,μ=8.439 mm-1,F(000)=864,R=0.0314 and wR=0.0733 for 1069 observed reflections (I > 2σ(I)). X-ray diffraction reveals that the title compound consists of the 2-D inorganic-organic hybrid sheet constructed from [CdBr2]n chains and bpdo bridges in the packing motif of…ABAB….The title compound exhibits intense blue photoluminescence in the solid state at room temperature.     

Integrated 2-D CE

A simple methodology for converting a commercial CE-MS instrument into an integrated 2-D CE system has been developed. The first-dimensional capillary operates as a typical CE instrument with UV/visible detection. Fractions leaving the first dimension are automatically collected and introduced into the second dimension, performed on a CE-MS apparatus, for analysis. The integrated system allows fractions in the second dimension to be analyzed using various electrophoretic modes. As an example, in this work we performed the separation of two families of antibiotics (nitroimidazoles and tetracyclines) in the first dimension and the subsequent resolution of the antibiotics in each family (nitroimidazoles were resolved by MEKC and tetracyclines by CZE) in the second dimension. The proposed system, which operates in an highly automatic manner, is flexible and allows various combination of electrophoretic modes to be implemented. In addition, the use of a mass spectrometer detector in the second dimension further increases the analytical potential of the system as a result of the high selectivity and wealth of structural information provided by the MS detector.     

Photo-cross-linkable polyelectrolyte multilayers for 2-D and 3-D patterning

We report the synthesis of poly(acrylic acid-ran-vinylbenzyl acrylate) (PAArVBA), a photo-cross-linkable weak polyelectrolyte, and its incorporation into polyelectrolyte multilayer (PEM) films. PEM films assembled from PAArVBA and poly(allylamine hydrochloride) (PAH) are found to exhibit similar thickness trends with assembly pH as those previously reported for poly(acrylic acid) (PAA)/PAH multilayers. Swelling properties of the as-built and photo-cross-linked films are studied by in situ ellipsometry. Two-dimensional masking techniques are used to pattern regions of high and low swelling, as confirmed by atomic force microscopy (AFM), and to provide spatial control over the low-pH-induced microporosity transition exhibited by PAH/PAA PEMs. Films containing alternating blocks of PAH/PAArVBA bilayers and PAH/PAA bilayers were assembled, laterally photopatterned, and exposed to low-pH solution to generate nanoporosity leading to patterned Bragg reflectors, thereby demonstrating three-dimensional control over film structure in these weak PEM assemblies.     

Experiments on 2-D suspensions

The rheological properties (velocity profile, viscosity) and the statistical distibution of objects in quasi-two-dimensional suspension of macroscopic spheres submitted to a shear is reported. The statistical data are analyzed by analogy with percolation.     

Controlled synthesis of 2-D and 3-D dendritic platinum nanostructures

Seeding and autocatalytic reduction of platinum salts in aqueous surfactant solution using ascorbic acid as the reductant leads to remarkable dendritic metal nanostructures. In micellar surfactant solutions, spherical dendritic metal nanostructures are obtained, and the smallest of these nanodendrites resemble assemblies of joined nanoparticles and the nanodendrites are single crystals. With liposomes as the template, dendritic platinum sheets in the form of thin circular disks or solid foamlike nanomaterials can be made. Synthetic control over the morphology of these nanodendrites, nanosheets, and nanostructured foams is realized by using a tin-porphyrin photocatalyst to conveniently and effectively produce a large initial population of catalytic growth centers. The concentration of seed particles determines the ultimate average size and uniformity of these novel two- and three-dimensional platinum nanostructures.     

Computational analysis of ligand recognition mechanisms by prostaglandin E2 (subtype 2) and D2 receptors

The eight members of the prostanoid receptor family belong to the class A G protein-coupled receptors. We investigated the evolutionary relationship of the eight members by a molecular phylogenetic analysis and found that prostaglandin E₂ receptor subtype 2 (EP₂) and prostaglandin D₂ receptor (DP) were closely related. The structures of the ligands for the two receptors are similar to each other but are distinguished by the exchanged locations of the carbonyl oxygen and the hydroxy group in the cyclopentane ring. The ligand recognition mechanisms of the receptors were examined by an integrated approach using several computational methods, such as amino acid sequence comparison, homology modeling, docking simulation, and molecular dynamics simulation. The results revealed the similar location of the ligand between the two receptors. The common carboxy group of the ligands interacts with the Arg residue on the seventh transmembrane (TM) helix, which is invariant among the prostanoid receptors. EP₂ uses a Ser on TM1 to recognize the carbonyl oxygen in the cyclopentane ring of the ligand. The Ser is specifically conserved within EP₂. On the other hand, DP uses a Lys on TM2 to recognize the hydroxy group of the ?? chain of the ligand. The Lys is also specifically conserved within DP. The interaction network between the D(E)RY motif and TM6 was found in EP₂. However, DP lacked this network, due to the mutation in the D(E)RY motif. Based on these observations and the previously published mutational studies on the motif, the possibility of another activation mechanism that does not involve the interaction between the D(E)RY motif and TM6 will be discussed.     

Zn-OH2 and Zn-OH complexes with hydroborate-derived tripod ligands: a comprehensive study

The complete array of those hydrotris(pyrazolyl/thioimidazolyl)borate ligands that were developed and used in the author's laboratories, with N3, N2S, NS2, and S3 donor sets, was scanned for their ability to form Zn-OH2 and Zn-OH complexes. The coordination motifs found were Zn-OH2, Zn-OH, Zn-OH-Zn, and Zn-O2H3-Zn. Of these, the well-established Zn-OH motif was complemented with novel species bearing N3, NS2, and S3 tripods. The Zn-OH2 motif was observed only with pyrazolylborate ligands and only in unusual situations with coordination numbers higher than 4 for zinc. The new Zn-OH-Zn motif was realized for three different pyrazolylborates, for one NS2 tripod, and for two S3 tripods. Finally, it was verified that the Zn-O2H3-Zn motif again occurs only with pyrazolylborate ligands. The new complexes were identified by a total of 11 structure determinations.     

Pushing around electrons: towards 2-D and 3-D molecular switches

In the new age of molecular electronics there has been a great deal of speculation about ways to control the passage of electrons through organic-based wires using electro- or photo-active switches. However, the next stage development is envisaged as the added sophistication of directionality so that electron migration can be switched into 2 and 3 dimensions. This short tutorial review will set out how this realisation may be achieved and highlight examples where the idea of directionality in electron transfer has been put into practice.     

Transformation of 1-D Chiral-chained Titanium Phosphate to 2-D Layer Structure Through a 1-D Zigzag Chain

The transformation of titanium phosphate from 1-D chiral- chain(JTP-A) to 2-D layer( TP-J1 ) has been carefully investigated. Through a hydrolysis-condensation self-assembly pathway, the crystals of TP-J1 can be obtained from the JTP-A phase under hydrothermal conditions. An intermediate material with zigzag chain during the transformation was observed by XRD characterization. A hypothesis of the transformation mechanism is also described in this article. It is noteworthy that ethylenediamine plays an important role in the transformation.     

蛋白质组衍生肽段文库用于鉴定酪蛋白激酶2的底物模体

模体是蛋白质二级结构上的一种特征序列,激酶底物通常具有一类特征性的模体,识别底物模体对鉴定激酶底物具有重要意义。为了快速鉴定激酶底物模体,将全细胞蛋白质酶解液作为肽段文库的来源,采用碱性磷酸酶去除肽段的固有磷酸化后构建了用于筛选激酶底物模体的肽段文库。该肽段文库是大量非磷酸化肽段的混合物,将此混合肽段与酪蛋白激酶2和三磷酸腺苷作用30 min后,通过固定化金属离子亲和色谱法富集磷酸化肽段,采用反相液相色谱-串联质谱分析,成功地鉴定到472条非冗余底物肽段,包含451个非冗余磷酸化位点,并由此得到底物模体S/T-D/E-x-D/E。该法能够快速准确地筛选出激酶底物模体,对研究激酶-底物识别以及信号转导过程具有重要意义。     

2-D array photonic crystal sensing motif

We have developed the first high-diffraction-efficiency two-dimensional (2-D) photonic crystals for molecular recognition and chemical sensing applications. We prepared close-packed 2-D polystyrene particle arrays by self-assembly of spreading particle monolayers on mercury surfaces. The 2-D particle arrays amazingly diffract 80% of the incident light. When a 2-D array was transferred onto a hydrogel thin film showing a hydrogel volume change in response to a specific analyte, the array spacing was altered, shifting the 2-D array diffraction wavelength. These 2-D array photonic crystals exhibit ultrahigh diffraction efficiencies that enable them to be used for visual determination of analyte concentrations.     

Synthesis of layered (2-D) V-based bimetallic oxalates from non-aqueous media that cannot be synthesized from aqueous media

The reaction of (NBu4)3[V(III)(ox)3] (1, ox = oxalate) and M(II) (M = Fe, Co, Ni, Cu) ions in MeCN, leads to the isolation of V-based coordination polymers of [N(n-Bu)4][Fe(II)V(II)I(ox)3].0.30[[N(n-Bu)4](BF4)] (2), [N(n-Bu)4][Co(II)V(III)(ox)3].0.75[[N(n-Bu)4](BF4)] (3), [N(n-Bu)4][Ni(II)V(III)(ox)3].0.20[[N(n-Bu)4](BF4)].0.20MeCN (4), and [N(n-Bu)4][Cu(II)V(III)(ox)2](BF4)2 (5) composition. Due to the lability of [V(III)(ox)3]3- to dissociate ox2-, these compounds cannot be prepared from aqueous media. 5 is best described as [N(n-Bu)4][V(III)Cu(II)(ox)2](BF4)2, and 2, 3, 4, and 5 are proposed to have a layered (2-D) motif for the MM(ox)x (x = 2, 3) extended framework. The [V(III)Cu(II)(ox)2] composition of 5 is reported for the first time for a bimetallic oxalate. 2 shows a weak antiferromagnetic interaction between Fe(II), S = 2 and V(III), S = 1 ions (theta = -9.4 K) within the 2-D layers. 3 and 5 do not magnetically order above 2 K. 4 magnetically order as ferromagnets below 2.55 K [taken as the onset of magnetization in chi'(T)], and has a glass transition temperature (chi'(max) at 1000 Hz) at 2.26 K.     

The NMR structure of [Xd(C2)]4 investigated by molecular dynamics simulations

The i‐motif tetrameric structure is built up from two parallel duplexes intercalated in a head‐to‐tail orientation, and held together by hemiprotonated cytosine pairs. Two topologies exist for the i‐motif structure, one with outermost 3′ extremities and the other with outermost 5′ extremities, called the 3′E and 5′E topology, respectively. Since the comparison of sugar and phosphate group interactions between the two topologies is independent of the length of the intercalation motif, the relative stability of the 3′E and 5′E topologies therefore should not depend on this length. Nevertheless, it has been shown that the 3′E topology of the [d(C2)]4 is much more stable than the 5′E topology, and that the former is the only species observed in solution. In order to understand the reason for this atypical behavior, the NMR structure of the [Xd(C2)]4 was determined and analyzed by molecular dynamics simulations. In the NMR structure, the width of the narrow groove is slightly smaller than in previously determined i‐motif structures, which supports the importance of phosphodiester backbone interactions in the structure stability. The simulations show that the stacking of cytosines, essential for the i‐motif stability, is produced by a similar and non‐negative twisting of the phosphodiester backbones. The twisting is induced by an interaction between the backbones; the [Xd(C2)]4 in 5′E topology, exhibiting very limited interaction between the phosphodiester backbones, is thus unstable. Copyright © 2002 John Wiley & Sons, Ltd.     

Hydrothermal synthesis and structural characterization of two 1-D and 2-D Dawson-based phosphotungstates

Two new Dawson-based phosphotungstates (H₂en)_0.5H[Cu(en)₂(H₂O)]₂{[Cu(en)₂](α₁-P₂W₁₇CuO₆₁)}·8H₂O (1) (en=ethylenediamine) and [4,4′-H₂bpy]₂{[Cu(4,4′-bpy)₃][Cu(4,4′-bpy)₄(H₂O)₂]₂[Cu(4,4′-bpy)][α-P₂W₁₈O₆₂]₂}·6H₂O (2) (4,4′-bpy=4,4′-bipyridine) have been hydrothermally synthesized and structurally characterized. 1 crystallizes in the triclinic space group P−1 with a=11.7626(17), b=13.246(2), c=29.350(5) Å, α=87.355(5), β=79.583(5), γ=66.993(3)°, V=4138.3(11) Å³, Z=2, GOF=1.089, R₁=0.0563 and wR₂=0.1505, whereas 2 belongs to the orthorhombic space group Iba2 with a=22.277(8), b=47.04(2), c=22.153(8) Å, V=23215(17) Å³, Z=4, GOF=1.051, R₁=0.0627 and wR₂=0.1477. 1 consists of a 1-D linear chain structure constructed from monocopper^II-substituted Dawson polyoxoanions, while 2 represents the first 2-D sheet-like structure with a (4,4)-connected topological net built up from plenary Dawson-type polyoxoanions and Cu^II-4,4′-bpy complex cations in polyoxometalate chemistry.     

Ordered 2-D and 3-D nanostructured amphiphile self-assembly materials stable in excess solvent

Amphiphile lyotropic liquid crystalline self-assembly materials are being used for a diverse range of applications. Historically, the most studied lyotropic liquid crystalline phase is probably the one-dimensional (1-D) lamellar phase, which has been employed as a model system for biomembranes and for drug delivery applications. In recent years, the structurally more complex 2-D and 3-D ordered lyotropic liquid crystalline phases, of which reversed hexagonal (H(2)) and reversed cubic phases (v(2)) are two prominent examples, have received growing interest. As is the case for the lamellar phase, these phases are frequently stable in excess water, which facilitates the preparation of nanoparticle dispersions and makes them suitable candidates for the encapsulation and controlled release of drugs. Integral membrane protein crystallization media and templates for the synthesis of inorganic nanostructured materials are other applications for 2-D and 3-D amphiphile self-assembly materials. The number of amphiphiles identified as forming nanostructured reversed phases stable in excess solvent is rapidly growing. In this article, different classes of amphiphiles that form reversed phases in excess solvent are reviewed, with an emphasis on linking phase behavior to amphiphile structure. The different amphiphile classes include: ethylene oxide-, monoacylglycerol-, glycolipid-, phosphatidylethanolamine-, and urea-based amphiphiles.     

The variational alternant molecular orbital method for 3-D and 2-D hydrogen molecule

The Variational alternant molecular orbital method (VAMO ) is described and applied to the case of three-dimensional and two-dimensional hydrogen molecules. The energies of the electron system are obtained, together with the equilibrium distances of the molecules. The intergrals equivelent to the Slater's integrals of the nonvariational method are described. Applications of this method to realizable systems are described.     

Review: Downsizing effect on 2-D and 3-D spin crossover metal-organic frameworks

This review is focused on the downsizing effect of a family of Hofmann-type Metal Organic Frameworks (MOFs) exhibiting Spin-Crossover Phenomenon (SCO) at high temperatures. Their nanoscale importance is currently under investigation concerning their multifunctional activity combining different properties such as magnetic, electrical, optical, or mechanical. General strategies for the fabrication of these materials in nanoscale will be presented as well as the development and optimization of thin film growth and nanopatterning methods. An analytical study of 2-D and 3-D tetracyanometallates SCO MOFs prepared both in their bulk form as well as nanoparticles will be outlined and the correlation of their magnetic properties with both their structures and sizes will be discussed.