Nachbargruppeneffekte bei der aminolyse von estern—I: Kinetik der aminolyse von nitrophenylacetaten mit n-butylamin in dioxan

The kinetics of the aminolysis of different nitrophenylacetates were investigated with n-butylamine in dioxane at 20°C. The reaction rate can be described up to high concentrations of amine (~1 mole dm^?3) by the equation v=k₂[ester][amine]+k₃[ester][amine]². The ratio $\text{k}{}_3\text{k}{}_2$ is larger for p-nitrophenylacetates than for o-nitrophenylacetates, while for 2,4-dinitrophenylacetates a third order term is not observed.     

The amniotic fluid cell proteome

Proteomic analysis of amniotic fluid cells may lead to the discovery of novel markers for embryonic abnormalities. A two-dimensional database for proteins of normal human amniotic fluid cells was constructed. The amniotic fluid cell extract was analyzed by two-dimensional gel electrophoresis and the proteins were identified by matrix-assisted laser desorption ionisation-time of flight-mass spectrometry. The database comprises 432 different gene products, which are in the majority enzymes, structural proteins, heat shock proteins, and proteins related to signal transduction. The obtained data show that the amniotic fluid population maybe either heterogeneous, originating from different fetal compartments and embryo tissues or is still pluripotent. Many proteins which are known to belong to certain cell types were found in the amnion cell fluid. This indicates that some types of fetal cells are already differentiated at the time of amniocentesis (about the 16(th) week of gestation). Moreover, the finding of proteins highly expressed in embryonic stem cells suggests that amniotic fluid could be used as a cell pool for transplantation therapy.     

SERS: a versatile tool in chemical and biochemical diagnostics

Raman spectroscopy is a valuable tool in various research fields. The technique yields structural information from all kind of samples often without the need for extensive sample preparation. Since the Raman signals are inherently weak and therefore do not allow one to investigate substances in low concentrations, one possible approach is surface-enhanced (resonance) Raman spectroscopy. Here, rough coin metal surfaces enhance the Raman signal by a factor of 10⁴–10¹⁵, depending on the applied method. In this review we discuss recent developments in SERS spectroscopy and their impact on different research fields.     

Core collapse supernovae in the QCD phase diagram

We compare two classes of hybrid equations of state with a hadron-to-quark matter phase transition in their application to core collapse supernova simulations. The first one uses the quark bag model and describes the transition to three-flavor quark matter at low critical densities. The second one employs a Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with parameters describing a phase transition to two-flavor quark matter at higher critical densities. These models possess a distinctly different temperature dependence of their transition densities which turns out to be crucial for the possible appearance of quark matter in supernova cores. During the early post-bounce accretion phase quark matter is found only if the phase transition takes place at sufficiently low densities as in the study based on the bag model. The increase critical density with increasing temperature, as obtained for our PNJL parametrization, prevents the formation of quark matter. The further evolution of the core collapse supernova as obtained applying the quark bag model leads to a structural reconfiguration of the central protoneutron star where, in addition to a massive pure quark matter core, a strong hydrodynamic shock wave forms and a second neutrino burst is released during the shock propagation across the neutrinospheres. We discuss the severe constraints in the freedom of choice of quark matter models and their parametrization due to the recently observed 2M _?? pulsar and their implications for further studies of core collapse supernovae in the QCD phase diagram.     

Neutrino-induced nucleosynthesis of A>64 nuclei: the nu p process

We present a new nucleosynthesis process that we denote as the nu p process, which occurs in supernovae (and possibly gamma-ray bursts) when strong neutrino fluxes create proton-rich ejecta. In this process, antineutrino absorptions in the proton-rich environment produce neutrons that are immediately captured by neutron-deficient nuclei. This allows for the nucleosynthesis of nuclei with mass numbers A>64, , making this process a possible candidate to explain the origin of the solar abundances of (92,94)Mo and (96,98)Ru. This process also offers a natural explanation for the large abundance of Sr seen in a hyper-metal-poor star.     

Surface-assisted coordination chemistry and self-assembly

This article discusses different approaches to build up supramolecular nanoarchitectures on surfaces, which were simultaneously investigated by scanning tunneling microscopy (STM) on the single-molecule level. Following this general road map, first, the hydrogen-bonding guided self-assembly of two different, structural-equivalent molecular building blocks, azobenzene dicarboxylic acid and stilbene dicarboxylic acid, was studied. Secondly, the coordination chemistry of the same building blocks, now acting as ligands in metal coordination reactions, towards co-sublimed Fe atoms was studied under near surface-conditions. Extended two-dimensional tetragonal network formation with unusual Fe2L(4/2)-dimers at the crossing points was observed on copper surfaces. Complementary to the first two experiments, a two-step approach based on the solution-based self-assembly of square-like tetranuclear complexes of the M4L4-type with subsequent deposition on graphite surfaces was investigated. One- and two-dimensional arrangements as well as single molecules of the M4L4-complexes could be observed. Moreover, the local electronic properties of a single M4L4-complexes could be probed with submolecular resolution by means of scanning tunnelling spectroscopy (STS).