Carboxy-terminated oligo(ethylene glycol)-alkane phosphate: synthesis and self-assembly on titanium oxide surfaces

The surface immobilization of oligo- and poly(ethylene glycol) on solids is a widely used approach to prevent the nonspecific adsorption of proteins, bacteria, and cells. A novel tri(ethylene glycol) derivative, phosphoric acid-mono(22-carboxy-12,15,18,21-tetraoxadocosyl) ester, was synthesized with the aim to produce self-assembled monolayers (SAMs) on metal/metal oxide surfaces. This compound contains two reactive, terminal moieties: the phosphoric acid group as anchor to the surface, and the carboxylic group as linker for further attachment of molecules such as peptides and proteins to be present at the surface. The adsorption on titanium-dioxide-coated substrates was studied quantitatively and the resulting SAMs were characterized by angle-dependent X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. XPS data showed that the monomolecular layer is attached with the phosphate group to the substrate, but not fully ordered. The dry adlayer thickness was determined to be 13.4 A, which is less than expected for a densely packed monolayer. Surface concentration calculated from ellipsometry data resulted in a grafting density of 2.03 molecules/nm2.     

Consistency of the intensional level of the Minimalist Foundation with Church’s thesis and axiom of choice

Consistency with the formal Church’s thesis, for short CT, and the axiom of choice, for short AC, was one of the requirements asked to be satisfied by the intensional level of a two-level foundation for constructive mathematics as proposed by Maietti and Sambin (in Crosilla, Schuster (eds) From sets and types to topology and analysis: practicable foundations for constructive mathematics, Oxford University Press, Oxford, 2005). Here we show that this is the case for the intensional level of the two-level Minimalist Foundation, for short MF, completed in 2009 by the second author. The intensional level of MF consists of an intensional type theory à la Martin-Löf, called mTT. The consistency of mTT with CT and AC is obtained by showing the consistency with the formal Church’s thesis of a fragment of intensional Martin-Löf’s type theory, called \(\mathbf{MLtt}_1\), where mTT can be easily interpreted. Then to show the consistency of \(\mathbf{MLtt}_1\) with CT we interpret it within Feferman’s predicative theory of non-iterative fixpoints \(\widehat{ID_1}\) by extending the well known Kleene’s realizability semantics of intuitionistic arithmetics so that CT is trivially validated. More in detail the fragment \(\mathbf{MLtt}_1\) we interpret consists of first order intensional Martin-Löf’s type theory with one universe and with explicit substitution rules in place of usual equality rules preserving type constructors (hence without the so called \(\xi \)-rule which is not valid in our realizability semantics). A key difficulty encountered in our interpretation was to use the right interpretation of lambda abstraction in the applicative structure of natural numbers in order to model all the equality rules of \(\mathbf{MLtt}_1\) correctly. In particular the universe of \(\mathbf{MLtt}_1\) is modelled by means of \(\widehat{ID_1}\)-fixpoints following a technique due first to Aczel and used by Feferman and Beeson.     

Hierarchical differential evolution for minimal cut sets identification: Application to nuclear safety systems

In this paper, we present a Hierarchical Differential Evolution (HDE) algorithm for minimal cut set (mcs) identification of coherent and non-coherent Fault Trees (FTs). In realistic application of large-size systems, problems may be encountered in handling a large number of gates and events. In this work, to avoid any approximation, mcs identification is originally transformed into a hierarchical optimization problem, stated as the search for the minimum combination of cut sets that can guarantee the best coverage of all the minterms that make the system fail: during the first step of the iterative search, a multiple-population, parallel search policy is used to expedite the convergence of the second step of the exploration algorithm. The proposed hierarchical method is applied to the Reactor Protection System (RPS) of a Pressurized Water Reactor (PWR) and to the the Airlock System (AS) of a CANadian Deuterium Uranium (CANDU) reactor. Results are evaluated with respect to the accuracy and computational demand of the solution found.     

Thiol‐ene and thiol‐yne‐based synthesis of glycodendrimers as nanomolar inhibitors of wheat germ agglutinin

Alkene and alkyne functional polyester‐based dendrimers of generation 1 to 4 have been prepared and reacted under free‐radical conditions with 2‐acetamido‐2‐deoxy‐1‐thio‐β‐D ‐glucose (GlcNAc‐SH). As the alkene‐dendrimers underwent the addition of one thiyl radical per ene group whereas each yne group of alkyne‐dendrimers was saturated by two thiyl radicals, a collection of glycodendrimers with glycan density ranging from six to ninety‐six GlcNAc per dendrimer was obtained. The recognition properties of the prepared glycodendrimers toward the wheat germ agglutinin (WGA) were evaluated by enzyme‐linked lectin assay (ELLA). The eight glycodendrimers were excellent ligands showing IC₅₀ values in the nanomolar range and relative potencies per sugar unit up to 2.27 e⁶ when compared to monosaccharidic GlcNAc used as monovalent reference. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2422–2433     

Straightforward Synthesis of (R,S)-β-Methyleneaspartic Acid, an Inhibitor of Glutamate-Aspartate Transaminase

A Baylis-Hillman adduct of methyl acrylate and ethyl glyoxalate was converted into the trichloroacetimidate that in the presence of DABCO rearranged to the corresponding trichloroacetamide. Eventually, hydrolysis under acidic conditions, led to the hydrochloride of racemic β-methyleneaspartic acid.     

Detecting Alzheimer's disease biomarkers: From antibodies to new bio-mimetic receptors and their application to established and emerging bioanalytical platforms – A critical review

The failure of therapeutic treatment of Alzheimer's disease (AD) patients can be related to the late onset of symptoms and, consequently, to a delayed pharmacological aid to counteract neurodegenerative progression. This is coupled to the fact that the diagnosis based on clinical criteria alone introduces high misdiagnosis rate. The availability of assessed biomarkers is therefore of crucial importance not only to counteract late diagnosis, but also to manage patients at high risk of AD development eligible for novel therapies. At the present time, amyloid-β peptides (Aβ_1-40 and Aβ_1-42 isoforms), alone or in combination with Tau protein (total and phosphorylated forms (p-tau)) constitute reliable AD biomarkers and result highly predictive of progression to AD dementia in patients with mild cognitive impairment (MCI), the earliest clinical presentation of AD. Improvement of existing diagnostic tools must take advantage of innovative bioanalytical approaches. In this review, starting from commercially available diagnostic platforms based on antibodies as recognition elements, we intended to provide a double point of view on the issue: 1) progresses achieved on innovative bioanalytical platforms (mainly sensors and biosensors) by using antibodies as consolidated receptors; 2) advance on promising bio-mimetic receptors alternative to antibodies in AD research, and their applications on conventional or innovative analytical platforms. In particular, we first focused on optical- (Propagating and Localized Surface Plasmon Resonance, named here SPR and LSPR) and electrochemical (voltammetric and impedimetric) transduction principles. Together with bioanalytical assays for AD biomarkers quantification, works aimed to investigate and understand their behavior, characteristics, and roles will also be considered in the discussion.     

Stereodivergent <Emphasis Type="Italic">Baylis-Hillman</Emphasis> Reaction of a Chiral Acryloyl Imide Exploiting Ion-Chelation Effect: Mechanistic Insight on the Rearrangement of Trichloroacetimidates of the <Emphasis Type="Italic">Baylis-Hillman</Emphasis> Adducts to Trichloroacetamides

Summary. In the presence of DABCO, ethyl glyoxalate and (4S,5R)-1,5-dimethyl-3-acryloyl-4-phenylimidazolidin-2-one gave mixtures of the corresponding Baylis-Hillman adducts enriched in either isomer, depending on the absence or the presence of LiClO₄ in the reaction mixture. A diastereomeric mixture in 10:90 dr allowed to definitively establish the mechanism of the reaction leading to trichloroacetamides starting from trichloroacetimidates of the Baylis-Hillman adducts.     

Synthesis of double core chromophore-functionalized nanothreads by compressing azobenzene in a diamond anvil cell

Carbon nanothreads are likely the most attracting new materials produced under high pressure conditions. Their synthesis is achieved by compressing crystals of different small aromatic molecules, while also exploiting the applied anisotropic stress to favor nontopochemical paths. The threads are nanometric hollow structures of saturated carbon atoms, reminiscent of the starting aromatic molecule, gathered in micron sized bundles. The examples collected so far suggest that their formation can be a general phenomenon, thus enabling the design of functionalities and properties by suitably choosing the starting monomer on the basis of its chemical properties and crystal arrangement. The presence of heteroatoms or unsaturation within the thread is appealing for improving the processability and tuning the electronic properties. Suitable simple chromophores can fulfill these requirements and their controlled insertion along the thread would represent a considerable step forward in tailoring the optical and electronic properties of these mechanically extraordinary materials. Here, we report the synthesis and extensive characterization of double core nanothreads linked by azo groups. This is achieved by compressing azobenzene in a diamond anvil cell, the archetype of a wide class of dyes, and represents a fundamental step in the realization of nanothreads with tailored photochemical and photophysical properties.

One-step high-pressure synthesis of 2D crystalline double nanothreads linked by azo groups.