A Preorganized Hydrogen-Bonding Motif for the Molecular Recognition of Carbohydrates

The choice between adaptive and preorganized architectures, or of the most effective hydrogen bonding groups to be selected, are dilemmas that supramolecular chemists must address in designing synthetic receptors for such a challenging guest as carbohydrates. In this paper, structurally related architectures featuring two alternative hydrogen bonding motifs were compared to ascertain the structural and functional origin of their binding differences and the advantages that can be expected in monosaccharide recognition. A set of structurally related macrocyclic receptors were prepared, and their binding properties were measured by NMR and ITC techniques in chloroform vs a common saccharidic target, namely, the β-octyl glycoside of D-glucose. Results showed that the diaminocarbazolic motif, recently reported as the constituting unit of highly effective receptors for saccharides in water, is a superior hydrogen bonding motif compared to the previously described diaminopyrrolic motif, which was successfully employed in molecular recognition of carbohydrates in polar organic solvents, due to intrinsic structural and functional factors, rather than to hydrophobic contributions. In addition, the occurrence of a rare example of a thermodynamic template effect exerted by the beta-glucoside has been ascertained, enhancing the synthesis outcome of the otherwise low yielding preparation of the described macrocyclic receptors.     

Synthesis of Copper-Based Nanostructures in Liquid Environments by Means of a Non-equilibrium Atmospheric Pressure Nanopulsed Plasma Jet

The influence of the liquid composition on the chemical and morphological properties of copper-based nanostructures synthesized by a non-equilibrium atmospheric plasma treatment is investigated and discussed. The synthesis approach is simple and environmentally friendly, employs a non-equilibrium nanopulsed atmospheric pressure plasma jet as a contactless cathode and a Cu foil as immersed anode. The process was studied using four distinct electrolyte solutions composed of distilled water and either NaCl?+?NaOH, NaCl only or NaOH only at two different concentrations, without the addition of any copper salts. CuO crystalline structures with limited impurities (e.g. Cu and Cu(OH)₂ phases) were produced from NaCl?+?NaOH containing solutions, mainly CuO and CuCl₂ structures were synthesized in the electrolyte solution containing only NaCl and no synthesis occurred in solutions containing only NaOH. Both aggregated and dispersed nanostructures were produced in the NaCl?+?NaOH and NaCl containing solutions. Reaction pathways leading to the formation of the nanostructures are proposed and discussed.     

D-β,β-dimethylcysteic acid,its preparation,structure, and spectroscopic properties

The X-ray crystal structure ofd-,-dimethylcysteic acid, C₅H₁₁NO₅S, has been determined. The compound is monoclinic, space groupP2₁₄ (No. 4), with cell dimensionsa=8.133(1),b=8.094(1),c=6.3138(7) Å,=96.36(1)° andZ=2. The structure was solved by Patterson and electron density difference methods and refined toR=0.025,R _w=0.022 for 1081 reflections. Bond lengths and angles do not differ from those in similar structures. The crystal is held together by intermolecular hydrogen bonds. The vibrational spectra have been recorded and assigned and the¹ H and¹³C NMR spectra were measured.     

Electrostatic self-organization of robust porphyrin-polyoxometalate films

Strategies to create thin films using layer-by-layer methods use oppositely charged polymeric polyelectrolytes for both or at least one component to beneficially exploit multitopic electrostatic interactions between the deposited layers with opposite charges. In contrast, the electrostatic deposition of tetracationic 5,10,15,20-tetrakis(1'-methyl-4'-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP(4+)) with tetraanionic polyoxometalates such as EuPW(11)O(39)(4-) or SiW(12)O(40)(4-) onto charged substrates, such as mica, or polar substrates, such as glass and indium-tin oxide (ITO), demonstrates that the use of polymeric components is not a priori necessary. The use of molecules in sequential dipping approaches requires a careful balance in the interaction energies between the oppositely charged molecules, as demonstrated by the observation that a tetraanionic porphyrin such as 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin does not form layers with TMPyP(4+). In the present case, these systems require several rounds of dipping to obtain films of uniform coverage and durability. The thin films deposited onto glass, quartz, ITO, and mica are surprisingly robust, since they are not removed by sonication in either organic solvents or 100 mM NaCl.     

Europium(III) reduction and speciation within a Wells-Dawson heteropolytungstate

The redox speciation of Eu(III) in the 1:1 stoichiometric complex with the alpha-1 isomer of the Wells-Dawson anion, [alpha-1-P 2W 17O 61] (10-), was studied by electrochemical techniques (cyclic voltammetry and bulk electrolysis), in situ XAFS (X-ray absorption fine structure) spectroelectrochemistry, NMR spectroscopy ( (31)P), and optical luminescence. Solutions of K 7[(H 2O) 4Eu(alpha-1-P 2W 17O 61)] in a 0.2 M Li 2SO 4 aqueous electrolyte (pH 3.0) show a pronounced concentration dependence to the voltammetric response. The fully oxidized anion and its reduced forms were probed by Eu L 3-edge XANES (X-ray absorption near edge structure) measurements in simultaneous combination with controlled potential electrolysis, demonstrating that Eu(III) in the original complex is reduced to Eu(II) in conjunction with the reduction of polyoxometalate (POM) ligand. After exhaustive reduction, the heteropoly blue species with Eu(II) is unstable with respect to cluster isomerization, fragmentation, and recombination to form three other Eu-POMs as well as the parent Wells-Dawson anion, alpha-[P 2W 18O 62] (6-). EXAFS data obtained for the reduced, metastable Eu(II)-POM before the onset of Eu(II) autoxidation provides an average Eu-O bond length of 2.55(4) A, which is 0.17 A longer than that for the oxidized anion, and consistent with the 0.184 A difference between the Eu(II) and Eu(III) ionic radii. The reduction of Eu(III) is unusual among POM complexes with Lindqvist and alpha-2 isomers of Wells-Dawson anions, that is, [Eu(W 5O 18) 2] (9-) and [Eu(alpha-2-As 2W 17O 61) 2] (17-), but not to the Preyssler complex anion, [EuP 5W 30O 110] (12-), and fundamental studies of materials based on coupling Eu and POM redox properties are still needed to address new avenues of research in europium hydrometallurgy, separations, and catalysis sciences.     

Tumor Carbohydrate Associated Antigen Analogs as Potential Binders for Siglec-7

We investigated two recently synthesized and characterized sialyl derivatives, bearing the Neu5Ac-α-(2-6)-Gal epitope, as promising binders for Siglec-7, an inhibitory Siglec mainly found on natural killer cells. A variety of sialoglycan structures can be recognized by Siglec-7 with implications in the modulation of immune responses. Notably, overexpression of sialylated glycans recognized by Siglec-7 can be associated with the progression of several tumors, including melanoma and renal cell carcinoma. NOE-based NMR techniques, including Saturation Transfer Difference and transferred-NOESY NMR, together with molecular docking and dynamic simulations were combined to shed light on the molecular basis of Siglec-7 recognition of two conformationally constrained Sialyl-Tn antigen analogs. We, therefore, identify the ligands epitope mapping and their conformational features and propose 3D models accurately describing the protein-ligand complexes. We found that the binding site of Siglec-7 can accommodate both synthetic analogs, with the sialic acid mainly involved in the interaction. Moreover, the flexibility of Siglec-7 loops allows a preferred accommodation of the more rigid compound bearing a biphenyl moiety at position 9 of the sialic acid that contributed to the interaction to a large extent. Our findings provided insights for developing potential novel high affinity ligands for Siglec-7 to hinder tumor evasion.     

Poly‐l‐Lactic Acid Nanofiber–Polyamidoamine Hydrogel Composites: Preparation,Properties, and Preliminary Evaluation as Scaffolds for Human Pluripotent Stem Cell Culturing

Electrospun poly‐l ‐lactic acid (PLLA) nanofiber mats carrying surface amine groups, previously introduced by nitrogen atmospheric pressure nonequilibrium plasma, are embedded into aqueous solutions of oligomeric acrylamide‐end capped AGMA1, a biocompatible polyamidoamine with arg‐gly‐asp (RGD)‐reminiscent repeating units. The resultant mixture is finally cured giving PLLA‐AGMA1 hydrogel composites that absorb large amounts of water and, in the swollen state, are translucent, soft, and pliable, yet as strong as the parent PLLA mat. They do not split apart from each other when swollen in water and remain highly flexible and resistant, since the hydrogel portion is covalently grafted onto the PLLA nanofibers via the addition reaction of the surface amine groups to a part of the terminal acrylic double bonds of AGMA1 oligomers. Preliminary tested as scaffolds, the composites prove capable of maintaining short‐term undifferentiated cultures of human pluripotent stem cells in feeder‐free conditions.

     

Coherent Superpositions of Photon Creation Operations and Their Application to Multimode States of Light

We present a concise review of recent experimental results concerning the conditional implementation of coherent superpositions of single-photon additions onto distinct field modes. Such a basic operation is seen to give rise to a wealth of interesting and useful effects, from the generation of a tunable degree of entanglement to the birth of peculiar correlations in the photon numbers and the quadratures of multimode, multiphoton, states of light. The experimental investigation of these properties will have an impact both on fundamental studies concerning, for example, the quantumness and entanglement of macroscopic states, and for possible applications in the realm of quantum-enhanced technologies.