Vibrational spectra and structure of cesium salts of icosahedral monocarba-closo-dodecarborate anion, [CB11H12]–, and its nido-derivative, [CB100H13]–

The Raman and IR spectra of the cesium salts of monocarbon carboranes, [closo-CB₁₁H₁₂]^– and [nido-CB₁₀H₁₃]^–, are reported and the assignment of the normal modes is given. Quantum-chemical calculations of the geometry of undistorted closo-anions B₁₂H₁₂ ^2– and CB₁₁H₁₂ ^– were carried out and normal coordinate analysis for the latter was performed. Structural parameters and spectral characteristics of isoelectronic closo-polyhedra [B₁₂H₁₂]^2–, [CB₁₁H₁₂]^–, and p-C₂B₁₀H₁₂ and those of the closo- and nido-structures were compared.     

Expression and Secretion of a CB4-1 scFv–GFP Fusion Protein by Fission Yeast

There is a rapidly growing demand for fluorescent single-chain Fv (scFv) antibody fragments for many applications. Yeasts have developed into attractive hosts for recombinant production of these functionalized proteins because they provide several advantages over prokaryotes and higher eukaryotes as expression systems, e.g., being capable of high-level secretion of heterologous proteins. In this study, we report Schizosaccharomyces pombe as a new host organism for secretory production of scFv-green fluorescent protein (GFP) fusions and compare it with previously described yeast expression systems. We cloned a plasmid for the expression and secretion of the anti-p24 (human immunodeficiency virus 1) CB4-1 scFv fused to GFP. After expression of the scFv–GFP fused to an N-terminal Cpy1 secretion signal sequence, fluorescence microscopy of living yeast cells indicated that the heterologous protein entered the secretory pathway. Western blot analysis of cell-free culture supernatants confirmed that the scFv–GFP was efficiently secreted with yields up to 5 mg/L. In addition, fluorescence measurements of culture supernatants demonstrated that the GFP moiety of the scFv–GFP protein is fully functional after secretion. Our data suggest that S. pombe has the potential for being used as alternative expression host in recombinant antibody fragment production by ensuring efficient protein processing and secretion.     

Convergent total syntheses of callipeltosides a, B, and C

Going for the hat-trick: The synthesis of the entire callipeltoside family of natural products is described. Key to this synthesis was the coupling of the di-ene-yne and pyran fragments by a diastereoselective alkenylzinc addition allowing rapid access to the common aglycon. Attachment of each relevant L-configured sugar resulted in the first total synthesis of callipeltoside B, and the syntheses of callipeltosides?A and C.     

Thermodynamics, kinetics, and photochemistry of β-strand association and dissociation in a split-GFP system

Truncated green fluorescent protein (GFP) that is refolded after removing the 10th β-strand can readily bind to a synthetic strand to recover the absorbance and fluorescence of the whole protein. This allows rigorous experimental determination of thermodynamic and kinetic parameters of the split system including the equilibrium constant and the association/dissociation rates, which enables residue-specific analysis of peptide-protein interactions. The dissociation rate of the noncovalently bound strand is observed by strand exchange that is accompanied by a color change, and surprisingly, the rate is greatly enhanced by light irradiation. This peptide-protein photodissociation is a very unusual phenomenon and can potentially be useful for introducing spatially and temporally well-defined perturbations to biological systems as a genetically encoded caged protein.     

Preparation of a novel,efficient, and recyclable magnetic catalyst,γ-Fe_2O_3@HAp-Ag nanoparticles,and a solvent- and halogen-free protocol for the synthesis of coumarin derivatives

In this protocol, Ag supported on the hydroxyapatite-core–shell magnetic γ-Fe_2O_3nanoparticles(γFe_2O_3@HAp-Ag NPs) as a novel, efficient, and magnetically recyclable catalyst is synthesized, and characterized by transmission electron microscopy(TEM), scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD), and vibrating sample magnetometry(VSM). The use of the catalyst is described in the synthesis of coumarin derivatives by the Pechmann condensation of various phenols with β-ketoesters under solvent- and halogen-free conditions at 80℃.This novel and inexpensive method offers advantages, such as recyclability simple experimental protocol, short reaction time, minimal work-up procedure, and excellent yields of products, together with desirable, eco-friendly, green aspects by avoiding toxic elements and solvents, and ease of recovery from the reaction mixture using an external magnet.     

Photoluminescence of a 5CB liquid crystal–organomontmorillonite nanoparticle heterocomposite

Photoluminescence (PL) of a heterocomposite, consisting of the nematic liquid crystal (LC) 4-pentyl-4´-cyanobiphenyl (5CB) and anisometric nanoparticles of montmorillonite (MMT) clay, modified by cetyltrimethylammonium bromide (CTAB) has been investigated at 4.2 and 300 K. The incorporation of this organoclay (B4) to 5CB decreases the emission intensity by 7–8 times due to efficient resonant quenching of the exciting energy by the organoclay. The spectrum shifts to a long-wave region, with this effect being considerably larger at low temperatures. Graphical separation of complex bands, corresponding to the bulk 5CB and 5СВ?+?В4 heterosystem at both temperatures revealed that the presence of the organoclay resulted in a significant growth of LC dimer quantity, shifting spectra towards longer wavelengths. Changes in the 5CB luminescence under organoclay influence can be explained by quite strong interphase interactions specified earlier by infrared spectroscopy between the MMT surface and LC, and by a realisation of more flat conformations of 5CB molecules. Confinement effects prevent full crystallisation of 5CB in the 5CB?+?B4 composite, and LC dimer structures located in the organoclay near-surface layers on the outer surface of the nanoparticles and inside its galleries remain in a larger amount, at low temperature, when compared to bulk 5CB. The remaining LC crystallises and photoluminescence from the 5CB monomers becomes intense.     

Synthesis,Crystal Structure and Photophysical properties of a Novel Molecule Containing a Triarylamine and an Oxadiazole Units

2-{3-[2-（4-N,N-Di-p-tolylaminophenyl)ethenyl]phenyl}-5-(4-bromophenyl)-1,3,4-oxadiazole(1) containing triarylamine and 2,5-diaryl-1,3,4-oxadiazole units was prepared by hornerWitting reactions.The structure of the compound was confirmed by ^1H NMR,IR ,MS and elemental analyses.The crystal structure of 1 was determined by X-ray diffraction analysis.UV absorpiton spectra and photoluminescent spectra were measured.     

Design, synthesis, and validation of a β-turn mimetic library targeting protein-protein and peptide-receptor interactions

The design and synthesis of a β-turn mimetic library as a key component of a small-molecule library targeting the major recognition motifs involved in protein-protein interactions is described. Analysis of a geometric characterization of 10,245 β-turns in the protein data bank (PDB) suggested that trans-pyrrolidine-3,4-dicarboxamide could serve as an effective and synthetically accessible library template. This was confirmed by initially screening select compounds against a series of peptide-activated GPCRs that recognize a β-turn structure in their endogenous ligands. This validation study was highlighted by identification of both nonbasic and basic small molecules with high affinities (K(i) = 390 and 23 nM, respectively) for the κ-opioid receptor (KOR). Consistent with the screening capabilities of collaborators and following the design validation, the complete library was assembled as 210 mixtures of 20 compounds, providing a total of 4200 compounds designed to mimic all possible permutations of 3 of the 4 residues in a naturally occurring β-turn. Unique to the design and because of the C(2) symmetry of the template, a typical 20 × 20 × 20-mix (8000 compounds prepared as 400 mixtures of 20 compounds) needed to represent 20 variations in the side chains of three amino acid residues reduces to a 210 × 20-mix, thereby simplifying the library synthesis and subsequent screening. The library was prepared using a solution-phase synthetic protocol with liquid-liquid or liquid-solid extractions for purification and conducted on a scale that insures its long-term availability for screening campaigns. Screening the library against the human opioid receptors (KOR, MOR, and DOR) identified not only the activity of library members expected to mimic the opioid receptor peptide ligands but also additional side-chain combinations that provided enhanced receptor binding selectivities (>100-fold) and affinities (as low as K(i) = 80 nM for KOR). A key insight to emerge from the studies is that the phenol of Tyr in endogenous ligands bearing the H-Tyr-Pro-Trp/Phe-Phe-NH(2) β-turn is important for MOR binding but may not be important for KOR (accommodated, but not preferred) and that the resulting selectivity for KOR observed with its removal can be increased by replacing the phenol OH with a chlorine substituent, further enhancing KOR affinity.     

Is Chromatography a Science, a Process, a Method, or a Scientific Discipline?

In the controversy over an article entitled Chromatography as a Scientific Discipline by V.G. Berezkin, it was pointed out that the subdivision of chromatographic processes into sorption–sieve chromatography and field nonsorption chromatography is inadmissible. It was demonstrated that all chromatographic processes, including flow fractionation in a transverse force field, are in principle two-phase (or polyphase) processes. It was illustrated that a longitudinal field in a flow cannot introduce a chromatographic component into the system. An additional definition of chromatography as a phenomenon was proposed on the basis of key points revealed by Professor Berezkin.     

Designed synthesis,structure, and 3-D topology of a supramolecular dimer and inorganic–organic cocrystal

Synthesis and structure of a supramolecular dimer and inorganic–organic cocrystal of composition [{Cu^IIL¹?(H₂O)}₂(C₈H₆O₄)] (1) are described (H₂L¹= N,N′-ethylenebis(3-ethoxysalicylaldimine); C₈H₆O₄ = terephthalic acid). Crystal engineering has been utilized for the designed synthesis of the title compound. Compound 1 crystallizes in a triclinic system with P 1 space group. The structure consists of terephthalic acid and two symmetry related inclusion products [Cu^IIL¹?(H₂O)], in which the water molecule is encapsulated in the O₄ compartment by forming bifurcated hydrogen bonds involving two hydrogen of water and phenolate and ethoxy oxygens of the compartmental ligand. Hydrogen bonding between encapsulated water molecules and terephthalic acid forms the supramolecular dimer. The title compound is an example of an inorganic–organic cocrystal as well. Weak interactions, such as semicoordination of phenoxo oxygen of one unit to the metal center of a symmetry related unit and C–H ··· O, and O–H ··· O hydrogen bonds result in generation of an overall 3-D topology in the title compound. The 3-D topology can be understood as interlinking of two different 2-D sheets.     

Dielectric constants of acetonitrile, γ-butyrolactone,propylene carbonate,and 1,2-dimethoxyethane as a function of pressure and temperature

The dielectric constants of 1,2-dimethoxyethane, acetonitrile, -butyrolactone, and propylene carbonate were determined from capacitance measurements extrapolated to infinite frequency; ln are reported as a function of pressure up to 80 MPa at 15, 25, 35, 45°C and as a function of temperature in the range 10 to 50°C at 0.10133 MPa. The variation of ln with temperature or pressure can be expressed by a second order polynomial expression. The isothermal compressibilities of the solvents were determined at 25°C from sound velocities, densities, and heat capacities. A simple correlation can be established between ln /P and for most aprotic solvent.     

Synthesis,characterization, luminescent,and catalytic performance of a dinuclear triazenido–silver complex

Our group has developed a series of molecular electrocatalysts for hydrogen generation based on triazenido–metal complexes (such as cobalt, copper, etc.). In this paper, we present the electrocatalytic performance of a new dinuclear silver complex, [Ag₂(L)₂], formed by reaction of the triazenido ligand, 1-[(2-carboxyethyl)benzene]-3-[benzimidazole]triazene (HL) with AgNO₃. The electrocatalytic systems based on this silver complex can afford 91.23 and 473 moles of hydrogen per mole of catalyst per hour (mol H₂/mol catalyst/h) from acetic acid at overpotential (OP) of 991.6 mV and an aqueous buffer at an OP of 837.6 mV, respectively. Electrochemical investigations show both the silver center and the triazenido ligand, HL, play important roles in determining the catalytic activities of the electrocatalytic system. Additionally, the triazenido ligand (HL) can serve as a fluorescent sensor for Ag⁺.     

Porpholactams and chlorolactams: replacement of a β,β'-double bond in meso-tetraphenyl-porphyrin and -chlorin by a lactam moiety

Reaction of meso-tetraphenylporpholactone with hydrazine converts the lactone moiety to an N-aminolactam. It also reduces the opposite pyrrolic moiety of both the starting material and the N-aminolactam, generating chlorin-like chlorolactone and N-aminochlorolactam, respectively. Reductive N-N cleavage of the N-aminoporpholactam generates the parent porpholactam.     

Large scale molecular dynamics simulations of a 4-n-pentyl-4′-cyanobiphenyl (5CB) liquid crystalline model in the bulk and as a droplet

Molecular dynamics simulations for 4-n-pentyl-4′-cyanobiphenyl (5CB) with as many as 944 molecules are reported. The order-N fast multipole method (FMM) is used to treat the long-range interactions. For a droplet of 944 molecules, the simulation shows a correlation between the droplet shape and the nematic order and a strong surface effect; little nematic order is found in a 118 molecule droplet. Simulations of the bulk system result in similar order parameters for both the 118 and 944 molecular ensembles. Although the nematic–isotropic transition was not observed at temperatures as high as 400 K using the CHARMM force field, a modification of the force field using ab initio determined partial atomic charges lowers the order parameters.     

Production, Purification, Immobilization, and Characterization of a Thermostable β-Galactosidase from Aspergillus alliaceus

A fungal strain isolated from rotten banana and identified as Aspergillus alliaceus was found capable of producing thermostable extracellular ??-galactosidase enzyme. Optimum cultural conditions for ??-galactosidase production by A. alliaceus were as follows: pH?4.5; temperature, 30?°C; inoculum age, 25?h; and fermentation time, 144?h. Optimum temperature, time, and pH for enzyme substrate reaction were found to be 45?°C, 20?min, and 7.2, respectively, for crude and partially purified enzyme. For immobilized enzyme?Csubstrate reaction, these three variable, temperature, time, and pH were optimized at 50?°C, 40?min, and 7.2, respectively. Glucose was found to inhibit the enzyme activity. The K _m values of partially purified and immobilized enzymes were 170 and 210?mM, respectively. Immobilized enzyme retained 43?% of the ??-galactosidase activity of partially purified enzyme. There was no significant loss of activity on storage of immobilized beads at 4?°C for 28?days. Immobilized enzyme retained 90?% of the initial activity after being used four times.     

Density and birefringence of a highly stable α,α,β-trisnaphthylbenzene glass

Spectroscopic ellipsometry has been used to understand the properties of α,α,β-trisnaphthylbenzene (ααβ-TNB) glasses vapor-deposited at a substrate temperature of 295 K (0.85 T(g)). In a single temperature ramping experiment, a range of properties of the as-deposited glass can be measured, including density, fictive temperature, onset temperature, thermal expansion coefficient, and birefringence. The vapor-deposited ααβ-TNB glass is 1.3% more dense than the ordinary glass prepared by cooling at 1 K/min, is found to be birefringent, has a fictive temperature 35 K below that of the ordinary glass, and an onset temperature 20 K above that of the ordinary glass. The thermal expansion coefficient of the vapor-deposited ααβ-TNB glass is 14% lower than that of the ordinary glass, indicating that lower portions of the potential energy landscape have more harmonic potential minima than the parts accessible to the ordinary glass.     

Design,Synthesis, and Antiviral Activity of α-Aminophosphonates Bearing a Benzothiophene Moiety

Abstract

A series of α-aminophosphonates containing a benzothiophene moiety was designed and synthesized. All synthesized compounds were confirmed by ¹H NMR, ¹³C NMR, ³¹P NMR, infrared spectroscopy, and elemental analysis. The half-leaf method was used to determine the in vivo efficacy of α-aminophosphonates bearing a benzothiophene moiety against the tobacco mosaic virus (TMV). Bioassay results showed that all compounds exhibited certain anti-TMV activity at 500 μg/mL concentration. Compound 2f exhibited a curative effect of up to 48.1% against TMV, which was almost similar to that obtained from the standard ningnanmycin (51.9%).

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text, figures, and tables.]     

Synthesis, structure and photoluminescent property of a novel potassic compound

A novel 3D coordination compound of K(H2TDA)(H20)(1)(H_3TDA=1H-1,2,3-triazole-4,5-dicarboxylic acid) has been prepared and characterized by IR spectroscopy,elemental analysis,ICP and single-crystal X-ray diffraction.Compound 1 displays strong fluorescent emission at room temperature.     

How strong is the interaction between a noble gas atom and a noble metal atom in the insertion compounds MNgF (M=Cu and Ag, and Ng=Ar, Kr, and Xe)?

Ab initio molecular orbital calculations have been carried out to investigate the structure and the stability of noble gas insertion compounds of the type MNgF (M=Cu and Ag, and Ng=Ar, Kr, and Xe) through second order Moller-Plesset perturbation method. All the species are found to have a linear structure with a noble gas-noble metal bond, the distance of which is closer to the respective covalent bond length in comparison with the relevant van der Waals limit. The dissociation energies corresponding to the lowest energy fragmentation products, MF+Ng, have been found to be in the range of -231 to -398 kJ/mol. The respective barrier heights pertinent to the bent transition states (M-Ng-F bending mode) are quite high for the CuXeF and AgXeF species, although for the Ar and Kr containing species the same are rather low. Nevertheless the M-Ng bond length in MNgF compounds reported here is the smallest M-Ng bond ever predicted through any experimental or theoretical investigation, indicating strongest M-Ng interaction. All these species (except AgArF) are found to be metastable in their respective potential energy surface, and the dissociation energies corresponding to the M+Ng+F fragments have been calculated to be 30.1-155.3 kJ/mol. Indeed, in the present work we have demonstrated that the noble metal-noble gas interaction strength in MNgF species (with M=Cu and Ag, and Ng=Kr and Xe) is much stronger than that in NgMF systems. Bader's [Atoms in molecules-A Quantum Theory (Oxford University Press, Oxford, 1990)] topological theory of atoms in molecules (AIM) has been employed to explore the nature of interactions involved in these systems. Geometric as well as energetic considerations along with AIM results suggest a partial covalent nature of M-Ng bonds in these systems. The present results strengthen our earlier work and further support the proposition on the possibility of experimental identification of this new class of insertion compounds of noble gas atoms containing noble gas-noble metal bond.