Calixarenes and related macrocycles as gene delivery vehicles

The success of gene therapy depends largely on the development of new efficient gene delivery vehicles. The emerging class of molecules for this application is macrocycles that feature persistent shape, thus ensuring higher level of supramolecular organization of the DNA complexes. The review focuses on recently developed calixarenes and close analogues as gene delivery vectors, their chemistry, ability to compact nucleic acids, transfection ability in vitro and cytotoxicity. Their fixed conformation with the possibility of multiple functional groups at the upper and lower rims allows preparation of cone-shaped macromolecules capable of programmed hierarchical assembly in the presence of DNA. It is shown that specially designed calixarenes, particularly those having amphiphilic structure with clustered DNA binding units, can form small virus-sized DNA nanoparticles with well-defined architecture, high transfection efficiency and low toxicity. The field is still largely underexplored so that there is a lot of room for further improvement of the molecular design of calixarenes. Moreover, their evaluation in vivo on animals will be an important step towards their validation for gene therapy.     

Pathways of Methane Transformation over Copper‐Exchanged Mordenite as Revealed by In Situ NMR and IR Spectroscopy

The reaction of methane with copper‐exchanged mordenite with two different Si/Al ratios was studied by means of in situ NMR and infrared spectroscopies. The detection of NMR signals was shown to be possible with high sensitivity and resolution, despite the presence of a considerable number of paramagnetic Cu^II species. Several types of surface‐bonded compounds were found after reaction, namely molecular methanol, methoxy species, dimethyl ether, mono‐ and bidentate formates, Cu^I monocarbonyl as well as carbon monoxide and dioxide, which were present in the gas phase. The relative fractions of these species are strongly influenced by the reaction temperature and the structure of the copper sites and is governed by the Si/Al ratio. While methoxy species bonded to Brønsted acid sites, dimethyl ether and bidentate formate species are the main products over copper‐exchange mordenite with a Si/Al ratio of 6; molecular methanol and monodentate formate species were observed mainly over the material with a Si/Al ratio of 46. These observations are important for understanding the methane partial oxidation mechanism and for the rational design of the active materials for this reaction.     

Novel reactions of ninhydrin oxime with mercaptoalkanoic acids

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Lewis acid-mediated mono- and bis-addition of C-nucleophiles to 1,3-dioxolan-4-ones

The reactions of 1,3-dioxolan-4-ones, readily available from α-hydroxy acids and aldehydes, with C-nucleophiles are described. Two possible reaction pathways resulting in O-substituted acids and tri-(hetero)arylmethanes are shown.     

Equation of State and Crystal Structure of NaAlSiO 4 with Calcium-Ferrite Type Structure in the Conditions of the Lower Mantle

The full profile refinement of the structure of the calcium-ferrite type NaAlSiO 4 was carried out at pressures up to 40 GPa. This high-pressure modification of NaAlSiO 4 is known to be stable at least to 75 GPa and 2450 K that corresponds to a middle part of the Earth's lower mantle. A zero-pressure unit cell volume V 0 =36.58(2) cm 3 /mol was obtained from a sample synthesized from natural albite. In situ pressure-volume data (with found V 0 ) was fitted to the Birch-Murnaghan equation of state, and it yielded the bulk modulus equal to 220(1) GPa and its pressure derivative equal to 4.1(1).     

High yield of graphene by dispersant-free liquid exfoliation of mechanochemically delaminated graphite

Journal of Nanoparticle Research - Orthorhombic titanic acid nanotubes (TAN) have large BET surface area and small-diameter one-dimensional nanotubular morphology, so they can work as a good...     

The Chromatic Spectrum of Mixed Hypergraphs

 A mixed hypergraph is a triple ℋ=(X, ?, ?), where X is the vertex set, and each of ?, ? is a list of subsets of X. A strict k-coloring of ℋ is a surjection c:X→{1,…,k} such that each member of ? has two vertices assigned a common value and each member of ? has two vertices assigned distinct values. The feasible set of H is {k: H has a strict k-coloring}. Among other results, we prove that a finite set of positive integers is the feasible set of some mixed hypergraph if and only if it omits the number 1 or is an interval starting with 1. For the set {s,t} with 2≤s≤t−2, the smallest realization has 2t−s vertices. When every member of ?∪? is a single interval in an underlying linear order on the vertices, the feasible set is also a single interval of integers. Received: May 24, 1999 Final version received: August 31, 2000     

WM groups and Ramsey theory

For amenable groups there are “correspondence principles” relating the behavior under group translation for sets of positive density to that of sets of positive invariant measure for ergodic actions of the group. When the group is also “minimally almost periodic” such actions are automatically weakly mixing; hence the name WM groups. We study here the combinatorial consequences of this state of affairs.     

Normal solvability of linear elliptic problemsRésolubilité normale des problèmes elliptiques linéaires

The paper is devoted to general linear elliptic problems in Hölder spaces. We consider unbounded domains and define limiting problems at infinity. We give a necessary and sufficient condition of normal solvability through uniqueness of solutions of limiting problems. We study a structure of spaces dual to Hölder spaces and specify the subspace of functionals, which provide the condition of normal solvability. This allows us to prove that for Fredholm operators all limiting operators are invertible. To cite this article: V. Volpert, A. Volpert, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 457–462.