Literatur

Analytical and Bioanalytical Chemistry -     

Synthesis and stereochemistry of some new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives

The synthesis and the stereochemistry of new 1,3,5-tris(1,3-dioxan-2-yl)-benzene derivatives are reported. The anancomeric structure and the axial orientation of the aryl group with respect to all 1,3-dioxane rings, and the cis-trans isomerism of some of the compounds are revealed. The data are supported by NMR investigations and by the molecular structure of one compound determined by single crystal X-ray diffractometry.     

A linear programming formulation of a semi-Markov model to design pig facilities

Housing facilities design represents the main strategic decision in pig farms. This paper introduces a linear programming formulation of a semi-Markov process to approach the facilities design. Thus, the Linear Programming formulation determines the optimum replacement policy and provides the equilibrium distribution of the herd along pig facilities. Then, the calculation of the associated needs of room for each sow facility is derived from sow herd distribution at equilibrium. Results show the flexibility of the model for designing pig facilities and computational advantages in the solving procedure compared to previous proposals. Furthermore, the robustness of the optimal solution is studied by means of sensitivity analysis.     

Sample preparation by in-gel digestion for mass spectrometry-based proteomics

The proteomic characterization of proteins and protein complexes from cells and cell organelles is the next challenge for investigation of the cell. After isolation of the cell compartment, three steps have to be performed in the laboratory to yield information about the proteins present. The protein mixtures must be separated into single species, broken down into peptides, and, finally, identified by mass spectrometry. Most scientists engaged in proteomics separate proteins by electrophoresis. For characterization and identification of proteomes, mass spectrometry of peptides is the method of choice. To combine electrophoresis and mass spectrometry, sample preparation by “in-gel digestion” has been developed. Many procedures are available for in-gel digestion, which inspired us to review in-gel digestion approaches. Figure Classical in-gel digestion process for a protein band stained with CBB. Protein bands are cut from the polyacrylamide gel (1). CBB molecules (blue circles) bound to the protein are released by iterative incubation in a buffered organic solvent system (2). To increase digestion efficiency and sequence coverage proteins are reduced (3) and alkylated (4). Proteins are subsequently digested with proteolytic enzymes (scissors symbols), typically trypsin (5). Trypsin cleaves at the amino acid residues arginine (R) and lysine (K). The resulting peptides (A, B, and C) are extracted from the polyacrylamide matrix (6). The peptide solution can be further purified for analysis by mass spectrometry (Section “Concentration and desalting of peptides”)     

Molecular rotors: design, synthesis, structural analysis, and silver complex of new [7.7]cyclophanes

New molecular rotors, [7.7](2,6)pyridinocyclophanes (monomers and dimers) embedding 1,3-dioxanes in the bridges, were investigated by variable-temperature NMR, molecular modeling, and single-crystal X-ray diffractometry. The nitrogen-inside rotation of the pyridine ring is more hindered in the derivatives with longer distance between the bridges (i.e., para > meta and 2,6-pyridylene > ortho) and can be chemically stopped by complexation with CF(3)SO(3)Ag. [structure: see text]     

Synthesis and Stereochemistry of Some New 1,3-Oxathiane Derivatives

Summary. The synthesis and stereochemistry of some new 2,5-substituted 1,3-oxathiane derivatives are reported. The anancomeric or flexible structure of the derivatives and some peculiar cases of prochirality are revealed by NMR investigations.