Automated Synthesis of 68Ga-Labeled DOTA-MGS8 and Preclinical Characterization of Cholecystokinin-2 Receptor Targeting

The new minigastrin analog DOTA-MGS8 targeting the cholecystokinin-2 receptor (CCK2R) used in this study displays the combination of two site-specific modifications within the C-terminal receptor binding sequence together with an additional N-terminal amino acid substitution preventing fast metabolic degradation. Within this study, the preparation of ⁶⁸Ga-labeled DOTA-MGS8 was validated using an automated synthesis module, describing the specifications and analytical methods for quality control for possible clinical use. In addition, preclinical studies were carried out to characterize the targeting potential. [⁶⁸Ga]Ga-DOTA-MGS8 showed a high receptor-specific cell internalization into AR42J rat pancreatic cells (~40%) with physiological expression of rat CCK2R as well as A431-CCK2R cells transfected to stably express human CCK2R (~47%). A favorable biodistribution profile was observed in BALB/c nude mice xenografted with A431-CCK2R cells and mock-transfected A431 cells as control. The high tumor uptake of ~27% IA/g together with low background activity and limited uptake in non-target tissue confirms the potential for high-sensitivity positron emission tomography of stabilized MG analogs in patients with MTC and other CCK2R-related malignancies.     

On pre-Λ-Sets and pre-v-Sets

We introduce the notions of a pre--set and a pre-V-set in a topological space. We study the fundamental properties of pre--sets and pre-V-sets and investigate the topologies defined by these families of sets.     

The 'apparent' hydrolysis of alkyl esters during electrospray ionization

Electrospray ionization (ESI) mass spectrometry was employed to obtain both molecular weight confirmation and structural information for a series of novel alkenyldiarylmethane (ADAM) analogs. The mass spectral data were intended for use during the structure elucidation of ester hydrolysis products formed during an in vitro metabolism study of a series of novel ADAM analogs. The data on the precursor molecules show the presence of the molecular ion peak, [M+H](+), as well as a peak consistent with the hydrolysis product of the original ester ([MH-ROH+H(2)O](+)). However, chemical ionization mass spectrometry, elemental analysis and (1)H NMR data indicated the presence of only the intact diester compounds, suggesting that the formation of the hydrolysis product was an instrumental artifact, i.e., in-beam hydrolysis during ESI or a result of longer ion residence times of the ion trap mass analyzer.     

Recent advances in CO2/epoxide copolymerization—New strategies and cooperative mechanisms

The catalytic copolymerization of CO₂ with epoxides has been known for over 40 years. Even though many heterogeneous and homogeneous catalyst systems have been developed, catalyst activity and selectivity still remain too low for large scale industrial application.Recent investigations have identified new copolymerization pathways with strong evidence for cooperative (bifunctional) mechanisms. At high dilutions, traditional discrete mononuclear single-site catalyst systems generally show a loss in activity. This effect can be overcome with the help of recently developed dinuclear and binary linked systems that involve cooperative mechanisms and thus permit high catalyst efficiency.This review gives an overview on the most recent advances in CO₂/epoxide copolymerization, new mechanistic studies and strategies for future catalyst developments.     

Dynamical Phase Transition for a Quantum Particle Source

We analyze the time evolution describing a quantum source for non-interacting particles, either bosons or fermions. The growth behavior of the particle number (trace of the density matrix) is investigated, leading to spectral criteria for sublinear or linear growth in the fermionic case, but also establishing the possibility of exponential growth for bosons. We further study the local convergence of the density matrix in the long time limit and prove the semi-classical limit.     

Zur Bestimmung des Nicotins durch Polarisation

Ohne Zusammenfassung     

LES of oxy-fuel jet flames using the Eulerian Stochastic Fields method with differential diffusion

The Eulerian Stochastic Fields (ESF) Monte Carlo method to solve the transported PDF (TPDF) equation is extended to account for differential diffusion effects by incorporating species individual molecular diffusivities. The method has been applied in Large Eddy simulation (LES) to non-piloted oxy-fuel jet flames at different Reynolds numbers experimentally investigated by Sevault et al. [1]. Due to the high H₂ content in the fuel stream and CO₂ in the oxidizer these flames pose new challenges to combustion modeling as the flame structures are different compared to CH₄/air flames. The simulations show very good agreement with the experiments in terms of mixture fraction conditional mean values for temperature and mayor species on the fuel lean side and the reaction zone, deviations on the fuel rich side are discussed. The trend and location of localized extinction is reproduced well in the simulations, as well as differential diffusion effects in the near field. Additionally, it is shown that a neglect of differential diffusion in the combustion model leads to a lifted flame.     

Allenyl esters as quenching agents for ruthenium olefin metathesis catalysts

In the attempt to synthesize substituted allenyl esters through a metathesis coupling of unsubstituted allenyl esters and alkenes using a variety of ruthenium catalysts, it was discovered that allenyl esters themselves cleanly arrested the activity of the catalysts. Further studies suggests possible utility of allene esters as general quenching agents for metathesis reactions. To explore this idea, several representative olefin metathesis reactions, including ring closing, were successfully terminated by the addition of simple allenyl esters for more convenient purification.