Effect of molecular weight on the exponential growth and morphology of hyaluronan/chitosan multilayers: a surface plasmon resonance spectroscopy and atomic force microscopy investigation

The layer-by-layer growth of multilayer assemblies of two polysaccharides, the polyanion hyaluronan (HA) and the polycation chitosan (CH), was investigated using atomic force microscopy (AFM) and surface plasmon resonance (SPR) spectroscopy, with primary emphasis on the effect of the polysaccharide molecular weights on the film thickness and surface morphology. The HA/CH multilayers exhibit an exponential increase of the optical film thickness with the number of deposited bilayers. We show that the multilayer thickness at a given stage depends on the size of both CH, the diffusing polyelectrolyte, and HA, the non-diffusing species. Assemblies (12 bilayers) of high molecular weight polysaccharides (HA, 360,000; CH, 160,000) were twice as thick (approximately 900 nm vs approximately 450 nm) as those obtained with low molecular weight polymers (HA, 30,000; CH, 31,000), as assessed by AFM scratch tests. The exponential growth rate is the same for the high and low molecular weight pairs; the larger film thicknesses observed by SPR and by AFM arising from an earlier onset of the steep exponential growth phase in the case of the high molecular weight pair. In all cases, isolated islets form during the deposition of the first CH layer onto the underlying HA. Upon further film growth, individual islets coalesce into larger vermiculate features. The transition from distinct islands to vermiculate structures depends on the molecular weights of the polysaccharides and the lower molecular weight construct presents larger worm-like surface domains than the high molecular weight pair.     

Synthesis and stereochemistry of tetrahydroprotoberberine derivatives

A series of 5-hydroxytetrahydroprotoberberines has been prepared from 3-aryltetrahydroisoquinoline derivatives via successive N-alkylation, oxidation and cyclization in acidic media. The relative configurations of the resulting diastereomeric 5-hydroxytetrahydroprotoberberines are reported.     

Enantioselective synthesis of 1-deoxy-d-gulonojirimycin from a phenylglycinol-derived lactam

Cyclocondensation of (R)-phenylglycinol with appropriately γ-substituted δ-oxo acid derivatives provides bicyclic lactams from which the enantioselective synthesis of 1-deoxy-d-gulonojirimycin has been reported.     

Use of electrospray mass spectrometry (ESI-MS) for the study of europium(III) complexation with bis(dialkyltriazinyl)pyridines and its implications in the design of new extracting agents

ESI mass spectrometry was used to investigate the europium complexation by tridentate ligands L identical with 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridines (DATP) that have shown unique separation properties of actinides(III) from lanthanides(III) in nitric acid solutions. Complexes of three ligands, namely methyl (DMTP), n-propyl (DnPTP), and iso-propyl (DiPTP), have been investigated in acidic solutions to check the aqueous-phase stability of Eu(L)(3)(3+) ions identified previously in the solid state. The data obtained show, first, the presence of stable Eu(L)(3)(3+) ions with DnPTP (log beta(3)(app) = 12.0 +/- 0.5) and DiPTP (log beta(3)(app) = 14.0 +/- 0.6) in methanol/water (1:1 v/v) solutions under pH range 2.8-4.6 and, second, a mechanism whereby alkyl moieties contribute to a self-assembling process leading to the formation of Eu(L)(3)(3+) ions. Other complexes such as Eu(L)(2)(3+) ions are only observed for DnPTP (log beta(2)(app) = 6.7 +/- 0.5) and DMTP (log beta(2)(app) = 6.3 +/- 0.1) and Eu(L)(3+) only for DMTP (log beta(1)(app) = 2.9 +/- 0.2). The log beta(n)(app) values for the Eu(L)(n)(3+) (n = 1-3) complexes were determined at pH 2.8. Better insight was given in this study concerning the role of the hydrophobic exterior of the ligands for the design of a new range of extracting agents.     

Luminescent PtII and PtIV Platinacycles with Anticancer Activity Against Multiplatinum-Resistant Metastatic CRC and CRPC Cell Models

Platinum-based chemotherapy persists to be the only effective therapeutic option against a wide variety of tumours. Nevertheless, the acquisition of platinum resistance is utterly common, ultimately cornering conventional platinum drugs to only palliative in many patients. Thus, encountering alternatives that are both effective and non-cross-resistant is urgent. In this work, we report the synthesis, reduction studies, and luminescent properties of a series of cyclometallated (C,N,N′)Pt^IV compounds derived from amine–imine ligands, and their remarkable efficacy at the high nanomolar range and complete lack of cross-resistance, as an intrinsic property of the platinacycle, against multiplatinum-resistant colorectal cancer (CRC) and castration-resistant prostate cancer (CRPC) metastatic cell lines generated for this work. We have also determined that the compounds are effective and selective for a broader cancer panel, including breast and lung cancer. Additionally, selected compounds have been further evaluated, finding a shift in their antiproliferative mechanism towards more cytotoxic and less cytostatic than cisplatin against cancer cells, being also able to oxidize cysteine residues and inhibit topoisomerase II, thereby holding great promise as future improved alternatives to conventional platinum drugs.     

Gas-phase reactivity of silver and copper coordinated monosaccharide cations studied by electrospray ionization and tandem mass spectrometry

The analytical distinction of the most common isomeric underivatized hexoses was investigated by means of mass spectrometry experiments. Electrospray ionization and tandem mass spectrometry were used in the analysis of silver and copper-coordinated monosaccharides (D-glucose, D-galactose, D-fructose, O-methyl-alpha-D-glucose and O-methyl-beta-D-glucose). The results show that cationization by Ag(+) allows the differentiation of the three first monosaccharides while the complexes formed by association of Cu(+) with these three monosacharides display a similar reactivity that prevents stereoisomer distinction. Unlike copper, silver adduct-ions of both alpha and beta anomeric O-methyl-D-glucoses exhibit specific decomposition patterns (i.e. a loss of methanol for the alpha-anomer and a loss of silver hydride for the beta-anomer), which allow an easy characterization. A theoretical survey of selected complexes, based on the use of DFT calculations were carried out on both anomers in order to rationalize the experimental findings.     

Approximation of the inductionless MHD problem using a stabilized finite element method

In this work, we present a stabilized formulation to solve the inductionless magnetohydrodynamic (MHD) problem using the finite element (FE) method. The MHD problem couples the Navier–Stokes equations and a Darcy-type system for the electric potential via Lorentz’s force in the momentum equation of the Navier–Stokes equations and the currents generated by the moving fluid in Ohm’s law. The key feature of the FE formulation resides in the design of the stabilization terms, which serve several purposes. First, the formulation is suitable for convection dominated flows. Second, there is no need to use interpolation spaces constrained to a compatibility condition in both sub-problems and therefore, equal-order interpolation spaces can be used for all the unknowns. Finally, this formulation leads to a coupled linear system; this monolithic approach is effective, since the coupling can be dealt by effective preconditioning and iterative solvers that allows to deal with high Hartmann numbers.