Kinetically inert ester bonds were used to attach monomers to a template, dictating the sequence of the polymer product.

Cadherin-mediated adhesion plays an important role in maintaining cell-cell contacts and reducing tumor metastasis. However, neo-expression of E-cadherin in ovarian carcinoma does not prevent the release and spread of cells from the primary tumor. Because caveolin-1 is down-regulated concomitantly with Ecad expression, we investigated whether the stability of adherens junctions in ovarian carcinoma was affected by caveolin-1 expression. We used IGROV1 cells transfected with caveolin-1 (IGtC3), mock-transfected control cells (IGtM87), and SKOV3 cells that endogenously express caveolin-1. Simultaneous expression of caveolin-1 and E-cadherin favored membrane distribution of E-cadherin and its associated catenin (p120ctn), even when caveolin-1 was only focally associated with adherens junctions. Silencing of caveolin-1 induced intracellular E-cadherin redistribution in IGtC3 and SKOV3 cells. Treatment with the specific src kinase inhibitor PP1 increased E-cadherin expression in IGtM87 and SKOV3 cells and enhanced membrane localization of both E-cadherin and p120ctn. However, PP1 could not completely reverse the detrimental effects on cell-cell adhesion induced by Ca Caveolin-1 (cav-1) is a 22-to 24-kd integral membrane protein present in numerous tissue types, which localizes in membrane subdomains called caveolae. Interaction of cav-1 with a variety of protein and nonprotein molecules results in pleiotropic effects on numerous cellular events such as signal transduction, gene regulation, lipid metabolism, and vesicular traffic.1-3 Down-regulation of cav-1 in human tumor samples of different histological origin has been documented, suggesting that this protein has a negative regulatory role in tumor development and acts as an onco-suppressor.4 -10 Although cav-1-null mice are no more prone to tumor development than are the cav-1-expressing counterparts, the null mice reveal an increased susceptibility to dysplastic mammary 11 or epidermal lesions 12 in the presence of an initial oncogenic stimulus. However, in a few tumor histotypes, cav-1 up-regulation has been associated with tumor progression and enhanced metastatic capability. 13,14In vitro, cav-1 expression is up-regulated in confluent cells, and the protein distributes in areas of cell-cell contacts, 15 in which molecules involved in intercellular cell adhesion, such as E-cadherin (E-cad), are localized. Ecad mediates cell-cell adhesion through calcium-dependent homophilic interaction of the extracellular domains forming cis-dimers on the same cell, which interact with cis-dimers on neighboring cells to generate trans-interactions. Stable cell-cell interactions require binding of catenins (cat) to the cytoplasmic domain of E-cad. Commonly, ␤-or ␥-cat bind the carboxy-terminal sequence of E-cad via armadillo-repeats and simultaneously interact with cytoplasmic ␣-cat to link the entire complex to the Supported by grants from Associazione Italiana Ricerca sul Cancro and the Cariplo Foundation.

No abstract

A new organic material assembled by dispersive forces exhibits stable one-dimensional channels suitable as the solid support in X-ray structural studies by the crystalline sponge method.

New tripodal squaramide-based hosts have been synthesised and structurally characterised by spectroscopic methods. In 2.5 % (v/v) [D(6)]DMSO in CDCl(3), compound 4 formed dimeric assemblies [log K(dim)=3.68(8)] as demonstrated by (1)H NMR spectroscopy and UV dilution experiments. AFM and SEM analyses revealed the formation of a network of bundled fibres, which indicates a preferential mechanism for aggregation. These C(3)-symmetric tripodal hosts exhibited two different and mutually exclusive modes of binding, each one easily accessible by simultaneous reorientation of the squaramide groups. In the first, a convergent disposition of the NH squaramide protons allowed the formation of an array of N-H⋅⋅⋅X(-) hydrogen bonds with anions. In the second mode, reorientation of carbonyl squaramide groups allowed multiple C=O⋅⋅⋅H interactions with ammonium cations. The titration of 4 with different tetraalkylammonium iodides persistently showed the formation of 1:1 complexes, as well as 1:2 and 1:3 complexes. The corresponding stoichiometries and binding affinities of the complexes were evaluated by multi-regression analysis. The formation of high-order complexes, supported by ROESY, NOESY and mass spectrometry experiments, has been attributed to the insertion of NR(4)I ion pairs between the carbonyl and NH protons of the squaramide groups located in adjacent arms of 4. The observed effects reflect the induction of significant conformational changes in the hosts, mainly in relation to the relative orientation of the squaramide groups adapting their geometries to incoming ion-pair complementary substrates. The results presented herein identify and fully describe two different modes of ion-pair recognition aimed at directing conformational transitions in the host, therefore establishing a base for controlling more elaborate movements of molecular devices through ion-pair recognition.