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Galectins are evolutionarily conserved and ubiquitously present animal lectins with a high affinity for b-galactose-containing oligosaccharides. To date, 15 mammalian galectins have been identified. Their involvement in cell-cell and cell-matrix interactions has highlighted their importance in signal transduction and other intracellular processes. Human galectin-7 (hGal-7) is a 15 kDa proto type galectin that forms a dimer in solution and its involvement in the stimulation and development of tumour growth has been reported. Previously, we reported the crystal structure of hGal-7 and its complex with galactose and lactose which provided insight into its molecular recognition and detailed interactions. Here, we present newly obtained high-resolution structural data on carbohydrate-based dendrons in complex with hGal-7. Our crystallographic data reveal how multivalent ligands interact with and form cross-links with these galectin molecules. Understanding how these dendrimeric compounds interact with hGal-7 would help in the design of new tools to investigate the recognition of carbohydrates by lectins. DatabaseThe atomic coordinates and structure factors for hGal-7-D1 (code 4UW3), hGal7-D2 (codes 4UW4, 4UW5) and hGal-7-D3 (code 4UW6) complexes have been deposited in the Protein

Nonlinear optical properties of push-pull stilbenes based on an alkylamino donor and a strong carbocation acceptor moieties are analyzed in the present study. The highly electron-acceptor character of the carbocation group makes this kind of molecule promising material for second-order nonlinear optical applications. Photoinduced intramolecular charge-transfer is studied by second harmonic generation in solution using time-resolved nondegenerate six-wave mixing. The fully characterized nonlinear dye Disperse Red 1 is used as a reference. The second-order nonlinear properties of the carbocation molecules are compared to a more standard amino-nitro push-pull stilbene. Kerr ellipsometry measurements aiming at a better understanding of the nonlinear excited state spectroscopy of the molecules are also reported. They reveal a very short excited state lifetime of the molecules. Optimization of this lifetime should lead to an improvement of the six-wave mixing response of such compounds.

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This paper presents calculations of dipole moments (mu), static polarizabilities (alpha), and first hyperpolarizabilities (beta) of phosphonic acid stilbene derivatives calculated in the framework of density functional theory. These calculations were performed using a finite field approach implemented in the density functional program ALLCHEM and were of an all-electron type using local exchange-correlation functional and specially designed basis sets. The molecular structures have been fully optimized using the semiempirical program MSINDO. Some of the investigated stilbenes have been synthesized very recently while others are described for the first time. Donor and acceptor groups of these analogues have been modified and the influence of these changes on the first hyperpolarizabilities has been investigated. This work demonstrates that the nonlinear optical response beta of these compounds increases dramatically when the acceptor moiety is displaced by analogues containing alkali metal groups. A general mechanism for the design of novel nonlinear optical materials with large first hyperpolarizabilities is described.