Formation and Fragmentation of Protonated Molecules after Ionization of Amino Acid and Lactic Acid Clusters by Collision with Ions in the Gas Phase

Collisions between O³⁺ ions and neutral clusters of amino acids (alanine, valine and glycine) as well as lactic acid are performed in the gas phase, in order to investigate the effect of ionizing radiation on these biologically relevant molecular systems. All monomers and dimers are found to be predominantly protonated, and ab initio quantum–chemical calculations on model systems indicate that for amino acids, this is due to proton transfer within the clusters after ionization. For lactic acid, which has a lower proton affinity than amino acids, a significant non‐negligible amount of the radical cation monomer is observed. New fragment‐ion channels observed from clusters, as opposed to isolated molecules, are assigned to the statistical dissociation of protonated molecules formed upon ionization of the clusters. These new dissociation channels exhibit strong delayed fragmentation on the microsecond time scale, especially after multiple ionization.     

Iridium(I)/N‐Heterocyclic Carbene Hybrid Materials: Surface Stabilization of Low‐Valent Iridium Species for High Catalytic Hydrogenation Performance

An Ir^I(NHC)‐based hybrid material was prepared using a methodology which allowed the precise positioning and isolation of the Ir centers along the pore channels of a silica framework. The full characterization of the material by solid‐state NMR spectroscopy showed that the supported Ir sites were stabilized by the silica surface, as low‐coordinated single‐site complexes. The material is extremely efficient for the hydrogenation of functional alkenes. The catalytic performance (TOF and TON) is one to two orders of magnitude higher than those of their molecular Ir analogues, and could be related to the prevention of the bimolecular deactivation of Ir complexes observed under homogeneous conditions.     

Paving the Way to Novel Phosphorus‐Based Architectures: A Noncatalyzed Protocol to Access Six‐Membered Heterocycles

Phosphorus‐based heterocycles provide access to materials with properties that are inaccessible from all‐carbon architectures. The unique hybridization of phosphorus gives rise to electron‐accepting capacities, a large variety of coordination reactions, and the possibility of controlling the electronic properties through phosphorus postfunctionalization. Herein, we describe a new noncatalyzed synthetic protocol to prepare fused six‐membered phosphorus heterocycles. In particular, we report the synthesis of novel phosphaphenalenes. These fused systems exhibit the benefits of both five‐ and six‐membered phosphorus heterocycles and enable a series of versatile postfunctionalization reactions. This work thus opens up new horizons in the field of conjugated materials.     

Maximally Prüfer Rings

In this paper we consider six Prüfer-like conditions on a commutative ring R, and introduce seventh condition by defining the ring R to be maximally Prüfer if R _M is Prüfer for every maximal ideal M of R, and we show that the class of such rings lie properly between Prüfer rings and locally Prüfer rings. We give a characterization of such rings in terms of the total quotient ring and the core of the regular maximal ideals. We also find a relationship of such rings with strong Prüfer rings.     

On the use of T-coercivity to study the interior transmission eigenvalue problem

In this Note, we investigate the so-called interior transmission problem using the T-coercivity approach. In particular, we prove that this problem, which appears when one is interested in the reconstruction of the support of an inclusion embedded in a homogeneous medium, is of Fredholm type and that so-called transmission eigenvalues form at most a discrete set. Our approach treats cases where the difference between the inclusion index and the background index can change sign, which are not covered by other techniques that can be found in the literature. We also provide Faber–Krahn type inequalities associated with this general case.     

Tuning the Protein‐Induced Absorption Shifts of Retinal in Engineered Rhodopsin Mimics

Rational design of light‐capturing properties requires understanding the molecular and electronic structure of chromophores in their native chemical or biological environment. We employ here large‐scale quantum chemical calculations to study the light‐capturing properties of retinal in recently designed human cellular retinol binding protein II (hCRBPII) variants (Wang et al. Science, 2012 , 338, 1340–1343). Our calculations show that these proteins absorb across a large part of the visible spectrum by combined polarization and electrostatic effects. These effects stabilize the ground or excited state energy levels of the retinal by perturbing the Schiff‐base or β‐ionone moieties of the chromophore, which in turn modulates the amount of charge transfer within the molecule. Based on the predicted tuning principles, we design putative in silico mutations that further shift the absorption properties of retinal in hCRBPII towards the ultraviolet and infrared regions of the spectrum.     

Derived Equivalence of Surface Algebras in Genus 0 via Graded Equivalence

We determine some of the derived equivalences of a class of gentle algebras called surface algebras. These algebras are constructed from an unpunctured Riemann surface of genus 0 with boundary and marked points by introducing cuts in internal triangles of an arbitrary triangulation of the surface. In particular, we fix a triangulation of a surface and determine when different cuts produce derived equivalent algebras.     

Influence of the Chain Length of Alkanethiols in Self‐Assembled Submonolayers on the Electrochemical Response of Aromatic Amine Mixtures

Alkanethiols, such as di‐n‐octadecyldisulfide, octanethiol, and ethanethiol, have been employed for self‐assembled monolayers on a gold electrode to study the influence of their chain length on the electrochemical response of aniline and 4‐aminobiphenyl. The responses of individual solutions and mixtures of both compounds show that the organization of the submonolayer built can improve the selectivity in the electrochemical analysis of those aromatic amines. The use of C8 10^?2 M allows the analysis of 4‐aminobiphenyl avoiding the aniline response. A better resolution for the analysis of those amine mixtures was obtained if a C18 10^?6 M modified gold electrode was used instead of an unmodified one.