Tailoring Disorder and Dimensionality: Strategies for Improved Solid Oxide Fuel Cell Electrolytes

Towards cooler solid oxide fuel cells: Disorder and dimensionality (see picture) play an important role in determining ion mobility of bulk and artificially nanolayered materials and should be considered in the design of new electrolytes with enhanced conductivity.

     

Characterization of green‐tissue protein extract from alfalfa (Medicago sativa) exploiting a 3‐D technique

There is a growing interest of pharmaceutical companies for plant‐based production systems. To facilitate the general acceptance of plants as bioreactors, the establishment of efficient downstream operations is critical. It has been proposed that a better understanding of the properties of the contaminant proteins can benefit downstream processing design and operation. The coupled application of 2‐DE with aqueous two‐phase partitioning has been suggested as a practical 3‐D method to characterize potential contaminant proteins from plant extracts. The application of this novel 3‐D approach to a complex protein extract from alfalfa (Medicago sativa) containing a model recombinant protein (human granulocyte colony stimulating factor (hG‐CSF)) resulted in the quantification of 55 protein spots. The 3‐D properties (M_r, pI, and K_p) obtained for 17 proteins comprising 69% of the alfalfa proteins, allowed the proposal of a prefractionation step as well as the identification of the target molecule (rG‐CSF) from bulk of alfalfa proteins. The information obtained from this experimental approach was useful for the identification of the potential contaminant proteins that will occur in alfalfa when this plant is used as a host for recombinant proteins. Additionally, this method will assist in the design of adequate purification strategies for recombinant proteins expressed in alfalfa green tissue.     

Study on the transannular bond formation and hypercoordination in tin and germanium spirometallocanes

D(CH₂CH₂S)₂MSNH(C₆H₄) (M = Ge, Sn; D = O, S) spirocycles were synthesized to analyze the influence of the decrease of the radius of the metal and the change of the hardness of donor atom on the strength of the transannular bond and the hypercoordination of group 14 elements. The compounds were characterized by IR, Raman and NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy, EI mass spectrometry and elemental analysis. Monocrystal X-ray diffraction analyses were made for the germanium compounds. The germaspirocycles were five-coordinated and had distorted trigonal bipyramid geometry. In contrast with most of the reported analogous germocanes, the transannular bond is stronger when the donor atom is oxygen, rather than sulfur. O(CH₂CH₂S)₂GeSNH(C₆H₄) exhibits an intramolecular hydrogen bond formation between the amine group and the transannular oxygen. The presence of this hydrogen bond determines whether the sulfur (O?Ge–S) or the nitrogen (S?Ge–N) of the five-member ring is the axial atom. According to the ¹¹⁹Sn chemical shift, both stannospirocycles were five-coordinated and therefore the presence of the transannular interaction in solution could be suggested.     

Connections between structure and performance of four cationic copolymers used as physically adsorbed coatings in capillary electrophoresis

In this work, the properties of four cationic copolymers synthesized in our laboratory are studied as physically adsorbed coatings for capillary electrophoresis (CE). Namely, the four copolymers investigated were poly(N-ethyl morpholine methacrylamide-co-N,N-dimethylacrylamide), poly(N-ethyl pyrrolidine methacrylate-co-N,N-dimethylacrylamide), poly(N-ethyl morpholine methacrylate-co-N,N-dimethylacrylamide) and poly(N-ethyl pyrrolidine methacrylamide-co-N,N-dimethylacrylamide). Capillaries were easily coated using these four different macromolecules by simply flushing into the tubing an aqueous solution containing the copolymer. The stability and reproducibility of each coating were tested for the same day, different days and different capillaries. It is demonstrated that the use of these coatings in CE can drastically reduce the analysis time, improve the resolution of the separations or enhance the analysis repeatability at very acidic pH values compared to bare silica columns. As an example, the analysis of an organic acids test mixture revealed that the analysis time was reduced more than 6-times whereas the separation efficiency was significantly increased to nearly 10-times attaining values up to 595,000 plates/m using the coated capillaries. Moreover, it was shown that all the copolymers used as coatings for CE allowed the separation of basic proteins by reducing their adsorption onto the capillary wall. Links between their molecular structure, physicochemical properties and their performance as coatings in CE are discussed.     

Biaryl Phosphite–Oxazoline Ligands from the Chiral Pool: Highly Efficient Modular Ligands for the Asymmetric Pd‐Catalyzed Heck Reaction

A highly modular library of readily available phosphite–oxazoline ligands L1 – L21 a – g was successfully applied in the asymmetric Pd‐catalyzed Heck reactions of several substrates and triflates under thermal and microwave conditions. This ligand library contains three main ligand structures that have been designed by systematic modification of one of the most successful ligand families developed for this process. As well as studying the effect of these three ligand structures on the catalytic performance, we also evaluated the effect of modifying several ligand parameters in these ligand structures. The effectiveness of these ligands at transferring the chiral information into the product can be tuned by correctly choosing the ligand components. Both enantiomers of the Heck coupling products were obtained in excellent activities (conversion: >100 % in 10 min), regioselectivities (>99 %) and enantioselectivities (>99 % ee). Under microwave‐irradiation conditions, the reaction times were considerably shorter (full conversion was achieved in a few minutes) and the regio‐ and enantioselectivities were still excellent.     

CAl4Be and CAl3Be2(-): global minima with a planar pentacoordinate carbon atom

Theoretical evidence for the first neutral and anionic global-minimum structures possessing a planar pentacoordinate carbon is reported.     

Theoretical Study of the Reactions M++CH3F (M=Ge,As, Se,Sb)

CASSCF–MRMP2 calculations have been carried out to analyze the reactions of the methyl fluoride molecule with the atomic ions Ge⁺, As⁺, Se⁺ and Sb⁺. For these interactions, potential energy curves for the low‐lying electronic states were calculated for different approaching modes of the fragments. Particularly, those channels leading to C? H and C? F oxidative addition products, H₂FC? M? H⁺ and H₃C? M? F⁺, respectively were explored, as well as the paths which evolve to the abstraction (M? F⁺+CH₃) and the elimination (CH₂M⁺+HF) asymptotes. For the reaction Ge⁺+CH₃F the only favorable channel leads to fluorine abstraction by the ion. As⁺ and Sb⁺ can react with CH₃F along pathways yielding stable addition products. However, a viable path joining the oxidative addition product H₃C? M? F⁺ with the elimination asymptote CH₂M⁺+HF was found for the reaction of the fluorocarbon compound with As⁺. No favorable channels were detected for the interaction of fluoromethane with Se⁺. The results discussed herein allow rationalizing some of the experimental data found for these interactions through gas‐phase mass spectrometry.     

GRASP and path relinking hybridizations for the point matching-based image registration problem

In the last decade, image registration has proven to be a very active research area when tackling computer vision problems, especially in medical applications. In general, image registration methods aim to find a transformation between two images taken under different conditions. Point matching is an image registration approach based on searching for the right pairing of points between the two images, which involves a combinatorial optimization problem. From this matching, the registration transformation can be inferred by means of numerical methods.     

Centers of quasi-homogeneous polynomial planar systems

In this paper we determine the centers of quasi-homogeneous polynomial planar vector fields of degree 0, 1, 2, 3 and 4. In addition, in every case we make a study of the reversibility and the analytical integrability of each one of the above centers. We find polynomial centers which are neither orbitally reversible nor analytically integrable, this is a new scenario in respect to the one of non-degenerate and nilpotent centers.     

A practical entry to β-aryl-β-alkyl amino alcohols: application to the synthesis of a potent BACE1 inhibitor

The 1,2-addition of alkyl Grignard reagents to readily available N-tert-butanesulfinyl ketimines, bearing an α-silyloxy substituent, proceeds in high yields and excellent diastereocontrol. The utility of the present method was demonstrated by the synthesis, in enantiomerically pure form, of one recently disclosed β-secretase (BACE1) inhibitor.