Influence of the pH Value on the Hydrothermal Degradation of Fructose

The hydrothermal treatment of sugars features a promising technology for the production of fine and platform chemicals from renewable resources. In this work the hydrothermal decomposition of fructose was studied in a buffered medium at a pH range between 2.2 and 8.0. It is demonstrated that at lower pH values mainly 5-hydroxymethylfurfural (HMF), levulinic acid and humin are generated, while lactic acid and acetic acid are produced at higher pH values. The work shows that the use of moderate acidic conditions may have advantages for the hydrothermal HMF production over the use of strongly acidic conditions, as especially the degradation into levulinic acid is suppressed. Besides, this study deals with a rather complex reaction network, hence limitations and need for adaption of the kinetic model are discussed.     

Die aktivierungsanalytische Bestimmung von Verunreinigungen in Platin

Ein Bericht über die aktivierungsanalytische Bestimmung des Cu, Au, Ir, Os und Ru in Platin durch radiochemische Trennung und gammaspektrometrische Strahlungsmessung. Aufbau eines radiochemischen Trenungsganges durch Verflüchtigung der Tetroxide des Os und Ru, Beseitigung der Matrixaktivität durch Adsorption am Anionenaustauscher, Extraktion des Au, Cu u. a. Elemente als Chloro-, DDTC- und BPHA-Komplexe. Diskussion der Möglichkeiten für den Einsatz des Trennungsganges in der Aktivierungsanalyse. Wiedergabe der Arbeitsvorschrift und der Ergebnisse der Analyse einiger Platinproben mit Verunreinigungen im Bereich von 0,05…400 ppm.     

Expanded Mercaptocalixarenes: A New Kind of Macrocyclic Ligands for Stabilization of Polynuclear Thiolate Clusters

The syntheses and properties of expanded 4-tert-butyl-mercaptocalix[4]arenes, in which the methylene linkers are replaced by −CH₂NRCH₂− or −CH₂NRCH₂− and −CH₂NRCH₂CH₂CH₂NRCH₂− units, are described. The new macrocycles were obtained in a step-wise manner, utilizing fully protected, i. e. S-alkylated, derivatives of the oxidation-sensitive thiophenols in the cyclisation steps. Reductive cleavage of the macrobicyclic or macrotricyclic intermediates ( 6 , 7 , 11 ) afforded the free thiophenols (H₄ 8 , H₄ 9 , and H₄ 12 ) in preparative yields as their hydrochloride salts. The protected proligands can exist in two conformations, resembling the “cone” and “1,3-alternate” conformations found for the parent calix[4]arenes. The free macrocycles do not show conformational isomerism, but are readily oxidized forming intramolecular disulfide linkages. Preliminary complexation experiments show that these expanded mercaptocalixarenes can serve as supporting ligands for tetranuclear thiolato clusters.     

Experimental separation of virtual photon exchange and electron transfer in interatomic coulombic decay of neon dimers

We investigate the interatomic Coulombic decay (ICD) of neon dimers following photoionization with simultaneous excitation of the ionized atom (shakeup) in a multiparticle coincidence experiment. We find that, depending on the parity of the excited state, which determines whether ICD takes place via virtual dipole photon emission or overlap of the wave functions, the decay happens at different internuclear distances, illustrating that nuclear dynamics heavily influence the electronic decay in the neon dimer.     

Propane‐1,2‐diols from Dilactides,Oligolactides, or Poly‐L‐lactic Acid (PLLA): From Plastic Waste to Chiral Bulk Chemicals

The preparation of racemic or enantioenriched propane‐1,2‐diol from dilactides, oligolactides, or poly‐L ‐lactic acid (PLLA) is described. The transformation is carried out as tandem reactions in MeOH, covering hydrolysis and subsequent hydrogenation by using copper chromite as a catalyst. The starting material present undesired side products of the PLLA synthesis or PLLA waste.     

A Phosphine Functionalized β-Diketimine Ligand for the Synthesis of Manifold Metal Complexes

A bis(diphenyl)-phosphine functionalized β-diketimine (PNac-H) was synthesized as a flexible ligand for transition metal complexes. The newly designed ligand features symmetrically placed phosphine moieties around a β-diketimine unit, forming a PNNP-type pocket. Due to the hard and soft donor atoms (N vs. P) the ligand can stabilize various coordination polyhedra. A complete series ranging from coordination numbers 2 to 6 was realized. Linear, trigonal planar, square planar, tetrahedral, square pyramidal, and octahedral coordination arrangements containing the PNac-ligand around the metal center were observed by using suitable metal sources. Hereby, PNac-H or its anion PNac⁻ acts as mono-, bi- and tetradendate ligand. Such a broad flexibility is unusual for a rigid tetradentate system. The structural motifs were realized by treatment of PNac-H with a series of late transition metal precursors, for example, silver, gold, nickel, copper, platinum, and rhodium. The new complexes have been fully characterized by single crystal X-ray diffraction, NMR, IR, UV/Vis spectroscopy, mass spectrometry as well as elemental analysis. Additionally, selected complexes were investigated regarding their photophysical properties. Thus, PNac-H proved to be an ideal ligand platform for the selective coordination and stabilization of various metal ions in diverse polyhedra and oxidation states.     

Photobodies: Light‐Activatable Single‐Domain Antibody Fragments

Photocaged antibody fragments, termed photobodies, have been developed that are impaired in their antigen‐binding capacity and can be activated by irradiation with UV light (365 nm). This rational design concept builds on the selective photocaging of a single tyrosine in a nanobody (a single‐domain antibody fragment). Tyrosine is a frequently occurring residue in central positions of the paratope region. o‐Nitrobenzyl‐protected tyrosine variants were incorporated into four nanobodies, including examples directed against EGFR and HER2, and photodeprotection restores the native sequence. An anti‐GFP photobody exhibited an at least 10 000‐fold impaired binding affinity before photodeprotection compared with the parent nanobody. A bispecific nanobody–photobody fusion protein was generated to trigger protein heterodimerization by light. Photoactivatable antibodies are expected to become versatile protein reagents and to enable novel approaches in diagnostic and therapeutic applications.     

Heavy-baryon properties with NLO accuracy in perturbative QCD

We present an analysis of the static properties of heavy baryons at next-to-leading order in the perturbative expansion of QCD. We obtain analytical next-to-leading order three-loop results for the two-point correlators of baryonic currents with one finite-mass quark field for a variety of quantum numbers of the baryonic currents. We consider both the massless limit and the HQET limit of the correlator as special cases of the general finite-mass formula and find agreement with previous results. We present closed-form expressions for the moments of the spectral density. We determine the residues of physical baryon states using sum-rule techniques.     

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Abstract List

Index abstracts