Dimethyl Carbonate as a Sacrificial Molecule for the Synthesis of 5‐Memebered N‐ and O‐Heterocycles

In the last twenty years DMC has been employed as an efficient methylating and methoxycarbonylating agent with several monodentate and bidentate nucleophiles, showing great selectivity and unexpected results. In this short review we report on yet another application of DMC chemistry i.e. the synthesis of 5‐membered N‐ and O‐heterocycles. In these reactions DMC acts as a sacrificial molecule since it is not present in the final products, but only in the reaction intermediates as an halogen‐free leaving group. This DMC‐based synthesis of heterocycles resulted of general application, as it is effective for aliphatic and aromatic 1,4‐diols, incorporating several functionalities (primary, secondary, tertiary, allylic, phenolic), as well as, for bifunctional compounds i.e. 4‐amino‐1‐butanol. This synthetic procedure was also employed for industrially relevant compounds such as (‐)‐norlabdane oxide and isosorbide showing to maintain the chiral integrity of the substrate. In one case intramolecular cyclisation of isosorbide was also observed to achieve a strained tricyclic derivative. Comparing this reaction methodology with a chlorine based procedure, the DMC‐mediated pathway is quantitative, occurs in one step, does not require any chlorine‐based chemical or strong acid and does not produce any chlorinated waste material.     

HR MAS NMR, powder XRD and Raman spectroscopy study of inclusion phenomena in ��CD nanosponges

Three different samples of ?? cyclodextrin nanosponges (CDNS) are prepared from ?? cyclodextrin (??CD) and pyromellitic dianhydride (PMA). CDNS are cross-linked, nanoporous materials whose pore size can be modulated by suitable choice of the CD/PMA molar ratio. In the presence of aqueous solutions they can swell giving rise to gel-like behavior. The Raman spectra of dry and water treated CDNS are described, with emphasis on the group vibration modes in the low frequency part of spectrum, sensitive to molecular environment and cross-linking degree, and on O?CH/C?CH vibration modes of dry/swollen CDNS, in turn providing information on the hydration dynamics. Powder X-ray diffraction data indicate low crystallinity and the presence of bulk water within the 3D polymer network. High resolution magic angle spinning (HR MAS) NMR spectroscopy is successfully used for investigation of swollen CDNS. The NMR signals of bulk and ??bound?? water indicate two different states of water molecules inside the gel. Probe solute fluorescein is used to spot on the diffusion properties inside the gel. In one case the diffusion coefficient of fluorescein measured in CDNS results one order of magnitude higher than that in D₂O. The acceleration effect uncovered indicates that the motion of fluorescein inside the porous gel is driven by both hydrodynamic and electrostatic factors.     

Fluorescence recovery after photobleaching reveals the biochemistry of nucleocytoplasmic exchange

Fluorescence recovery after photobleaching (FRAP) can help unveil subtle dynamical and biochemical properties of intracellular components. A peculiar aspect of this method is that it is based on the change of optical properties only, whereas dynamics and biochemistry of the molecules of interest are not perturbed. This makes FRAP particularly suitable for the study of protein translocation, e.g., between nucleus and cytoplasm. Here we present a comprehensive theoretical treatment of FRAP applied to protein nucleocytoplasmic translocation by passive diffusion and/or energy-driven processes across the nuclear envelope. Our mathematical model is validated by experimental FRAP studies with functionalized fluorescent protein chimeras. Using this approach we demonstrate that molecular crowding at the nuclear pore does not hamper passive diffusion and calculate the dimension of the nuclear pore size (5.33 nm). Additionally, our FRAP analysis reveals the biochemical parameters (maximum translocation rate and dissociation constant of the transport complex in cytoplasm) associated with the active import of a prototypical nuclear localization sequence (NLS of SV40) and related mutants. We demonstrate that transportin binding and active import into the nucleus are independent processes that can be separately modulated. The present results are discussed in light of their potential to help in engineering sequences for intracellular targeted delivery of sensors and/or therapeutic compounds. Finally, the limits of validity of our mathematical model are addressed.     

Stabilization of Copper Catalysts for Liquid‐Phase Reactions by Atomic Layer Deposition

Atomic layer deposition (ALD) of an alumina overcoat can stabilize a base metal catalyst (e.g., copper) for liquid‐phase catalytic reactions (e.g., hydrogenation of biomass‐derived furfural in alcoholic solvents or water), thereby eliminating the deactivation of conventional catalysts by sintering and leaching. This method of catalyst stabilization alleviates the need to employ precious metals (e.g., platinum) in liquid‐phase catalytic processing. The alumina overcoat initially covers the catalyst surface completely. By using solid state NMR spectroscopy, X‐ray diffraction, and electron microscopy, it was shown that high temperature treatment opens porosity in the overcoat by forming crystallites of γ‐Al₂O₃. Infrared spectroscopic measurements and scanning tunneling microscopy studies of trimethylaluminum ALD on copper show that the remarkable stability imparted to the nanoparticles arises from selective armoring of under‐coordinated copper atoms on the nanoparticle surface.     

Determination of eight polyphenols and pantothenic acid in extra‐virgin olive oil samples by a simple,fast, high‐throughput and sensitive ultra high performance liquid chromatography with tandem mass spectrometry method

A new ultra high performance liquid chromatography coupled with tandem mass spectrometry method for a fast and sensitive determination of eight polyphenols (hydroxytyrosol, catechin, epicatechin, epigallocatechin gallate, oleuropein, quercetin, rutin, tyrosol) and panthotenic acid in extra‐virgin olive oil was developed. The method does not require long sample pre‐treatment and presents the lowest limit of detection and limit of quantitation values present in literature. Inter‐ and intra‐day variability, linear dynamic range of the calibration curve, recovery and matrix effect were also determined and investigated. The method was applied to several oil samples of different type and origin. Given its accuracy, precision and rapidity, the method is characterized by an interestingly high throughput, reliability, and sensitivity.     

High-content analysis of kinase activity in cells

High-content analysis (HCA) is a term used to describe techniques involving multiplexed analysis of fluorescent markers to measure multiple cellular responses to biological stimuli or drug treatment. HCA is usually based on automated microscopy or related technologies, and its value lies in providing multiparametric information on single cells within a population. During the last decade, several HCA approaches have been developed and applied to assess cellular mechanism of action of pharmacologically relevant compounds identified through biochemical screening or similar in vitro methods. With automation and instrument development, these approaches have evolved to the extent that the technique is now routinely used in screening applications, including primary HTS on compound collections. Here, we review the field and discuss in particular the application of HCA to the discovery of small molecule inhibitors targeting kinases which are implicated in Oncology.     

Identification of the tyrosine nitration sites in human endothelial nitric oxide synthase by liquid chromatography-mass spectrometry

The formation of nitric oxide (NO) in biological systems has led to the discovery of a number of post- translational protein modifications that can affect biological conditions such as vasodilation. Studies both from our laboratory and others have shown that beside its effect on cGMP generation from soluble guanylate cylcase, NO can produce protein modifications through both S-nitrosylation of cysteine residues. Previously, we have identified the potential S-nitrosylation sites on endothelial NO synthase (eNOS). Thus, the goal of this study was to further increase our understanding of reactive nitrogen protein modifications of eNOS by identifing tyrosine residues within eNOS that are susceptible to nitration in vitro. To accomplish this, nitration was carried out using tetranitromethane followed by tryptic digest of the protein. The resulting tryptic peptides were analyzed by liquid chromatography/mass spectrometry (LC/MS) and the position of nitrated tyrosines in eNOS were identified. The eNOS sequence contains 30 tyrosine residues and our data indicate that multiple tyrosine residues are capable of being nitrated. We could identify 25 of the 30 residues in our tryptic digests and 19 of these were susceptible to nitration. Interstingly, our data identified four tyrosine residues that can be modified by nitration that are located in the region of eNOS responsible for the binding to heat shock protein 90 (Hsp90), which is responsible for ensuring efficient coupling of eNOS.     

Light scattering investigation of association phenomena in saline carrageenan solutions

Intermolecular association of ι- and κ-carrageenan in aqueous solution has been studied by wide-angle laser light scattering as a function of salt composition and temperature. For ι-carragenan, the effect of three different salts (LiCl, NaCl, NaI) on the associative properties was investigated. As to κ-carrageenan, the association-inducing effect of Cs⁺ ions was studied, with particular interest in the time dependence of the aggregation process.     

On the Swendsen-Wang dynamics. I. Exponential convergence to equilibrium

We present rigorous results on the exponential convergence to equilibrium for the Swendsen-Wang stochastic dynamics for thed-dimensional Ising ferromagnet with external magnetic fieldh in the thermodynamic limit. We consider various situations, mainly in the low-temperature regime, in which boundary conditions are homogeneous and parallel or opposite to the external field. In the latter case we relate directly the tunneling from the metastable phase to the stable one with the exponential convergence to equilibrium.     

Markov bases and subbases for bounded contingency tables

In this paper we study the computation of Markov bases for contingency tables whose cell entries have an upper bound. It is known that in this case one has to compute universal Gröbner bases, and this is often infeasible also in small- and medium-sized problems. Here we focus on bounded two-way contingency tables under independence model. We show that when these bounds on cells are positive the set of basic moves of all 2 × 2 minors connects all tables with given margins. We also give some results about bounded incomplete table and we conclude with an open problem on the necessary and sufficient condition on the set of structural zeros so that the set of basic moves of all 2 × 2 minors connects all incomplete contingency tables with given positive margins.