Automated high content screening for phosphoinositide 3 kinase inhibition using an AKT 1 redistribution assay

High Content Screening (HCS), a combination of fluorescence microscopic imaging and automated image analysis, has become a frequently applied tool to study test compound effects in cellular disease-modelling systems. In this work, we established a medium to high throughput HCS assay in the 384-well format to measure cellular type I phosphoinositide 3 kinase (PI3K) activity. Type I PI3K is involved in several intracellular pathways such as cell survival, growth and differentiation as well as immunological responses. As a cellular model system we used Chinese Hamster Ovary (CHO) cells that had been stably transfected with human insulin receptor (hIR) and an AKT1-enhanced green fluorescent protein (EGFP) fusion construct. Upon stimulation of the hIR with insulin-like growth factor-1 (IGF-1), PI3K was activated to phosphorylate phosphatidylinositol (PtdIns)-4,5-bisphosphate at the 3-position, resulting in the recruitment of AKT1-EGFP to the plasma membrane. The AKT1-EGFP redistribution assay was robust and displayed little day-to-day variability, the quantification of the fluorescence intensity associated with plasma membrane spots delivered good Z' statistics. A novel format of compound dose-response testing was employed using serial dilutions of test compounds across consecutive microtiter plates (MTPs). The dose response testing of a PI3K inhibitor series provided reproducible IC50 values. The profiling of the redistribution assay with isoform-selective inhibitors indicates that PI3Kalpha is the main isoform activated in the CHO host cells after IGF-1 stimulation. Toxic compound side effects could be determined using automated image analysis. We conclude that the AKT1-EGFP redistribution assay represents a solid medium/high throughput screening (MTS/HTS) format to determine the cellular activity of PI3K inhibitors under conditions of growth factor stimulation.     

Barium

Ohne Zusammenfassung     

Elucidating Diphosphoinositol Polyphosphate Function with Nonhydrolyzable Analogues

The diphosphoinositol polyphosphates (PP‐IPs) represent a novel class of high‐energy phosphate‐containing messengers which control a wide variety of cellular processes. It is thought that PP‐IPs exert their pleiotropic effects as allosteric regulators and through pyrophosphorylation of protein substrates. However, most details of PP‐IP signaling have remained elusive because of a paucity of suitable tools. We describe the synthesis of PP‐IP bisphosphonate analogues (PCP‐IPs), which are resistant to chemical and biochemical degradation. While the two regioisomers 1PCP‐IP₅ and 5PCP‐IP₅ inhibited Akt phosphorylation with similar potencies, 1PCP‐IP₅ was much more effective at inhibiting its cognate phosphatase hDIPP1. Furthermore, the PCP analogues inhibit protein pyrophosphorylation because of their inability to transfer the β‐phosphoryl group, and thus enable the distinction between PP‐IP signaling mechanisms. As such, the PCP analogues will find widespread applications for the structural and biochemical characterization of PP‐IP signaling properties.     

Carbon isotope ratio measurements of glyphosate and AMPA by liquid chromatography coupled to isotope ratio mass spectrometry

The interest in compound-specific isotope analysis for product authenticity control and source differentiation in environmental sciences has grown rapidly during the last decade. However, the isotopic analysis of very polar analytes is a challenging task due to the lack of suitable chromatographic separation techniques which can be used coupled to isotope ratio mass spectrometry. In this work, we present the first method to measure carbon isotope compositions of the widely applied herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA) by liquid chromatography coupled to isotope ratio mass spectrometry. We demonstrate that this analysis can be carried out either in cation exchange or in reversed-phase separation modes. The reversed-phase separation yields a better performance in terms of resolution compared with the cation exchange method. The measurement of commercial glyphosate herbicide samples show its principal applicability and reveals a wide range of δ¹³C values between ?24 and ?34 ‰ for different manufacturers. The absolute minimum amounts required to perform a precise and accurate determination of carbon isotope compositions of glyphosate and AMPA were in the sub-microgram range. The method proposed is sensitive enough to further perform the experiments that are necessary to better understand the carbon isotope fractionation associated to the natural degradation of glyphosate into AMPA. Furthermore, it can be used for contaminant source allocation and product authenticity as well.     

Wiring edge-disjoint layouts

We consider the wiring or layer assignment problem for edge-disjoint layouts. The wiring problem is well understood for the case that the underlying layout graph is a square grid (Lipski Jr. and Preparata, 1987). In this paper, we introduce a more general approach to this problem. For an edge-disjoint layout in the plane, respectively in an arbitrary planar layout graph, we give equivalent conditions for k-layer wirability. Based on these conditions, we obtain linear-time algorithms to wire every layout in a tri-hexagonal grid or a tri-square-hexagonal grid, respectively, using at most five layers.     

A generalization of the zero–one principle for sorting algorithms

In this paper a new general approach for the so-called “zero-one principle” for sorting algorithms is described. A theorem from propositional logic that states the connection between two-valued logic and many-valued logic is used to prove this zero-one principle. As a consequence a zero-one principle for a more general class of sorting algorithms is derived.     

Generalized Fibonacci recurrences and the lex-least de Bruijn sequence

The skew of a binary string is the difference between the number of zeroes and the number of ones, while the length of the string is the sum of these two numbers. We consider certain suffixes of the lexicographically-least de Bruijn sequence at natural breakpoints of the binary string. We show that the skew and length of these suffixes are enumerated by sequences generalizing the Fibonacci and Lucas numbers, respectively.     

On-shell Extension of Distributions

We consider distributions on \({\mathbb{R}^{n}{\setminus}\{0\}}\) which satisfy a given set of partial differential equations and provide criteria for the existence of extensions to \({\mathbb{R}^n}\) that satisfy the same set of equations on \({\mathbb{R}^n}\) . We use the results to construct distributions satisfying specific renormalisation conditions in the Epstein and Glaser approach to perturbative quantum field theory. Contrary to other approaches, we provide a unified approach to treat Lorentz covariance, invariance under global gauge group and almost homogeneity, as well as discrete symmetries. We show that all such symmetries can be recovered by applying a linear map defined for all degrees of divergence. Using similar techniques, we find a relation between on-shell and off-shell time-ordered products involving higher derivatives of the fields.     

Rare-Earth Metal Diimide Complexes via Alkylaluminate Templating,Including a Ceric Derivative

Protonolysis of lanthanide tris(tetramethylaluminate)s with two equivalents of 2,6-diisopropylaniline affords La^III and Ce^III diimide compounds Ln[(μ-NC₆H₃iPr₂-2,6)₂AlMe₂](thf)₄ featuring a bidentate AlMe₂-linked diimido ligand. As revealed for the corresponding Ce(GaMe₄)₃-reaction, formation of the diimide complexes proceeds via tetrametallic complexes of the type [Ce{(μ-NC₆H₃iPr₂-2,6)(HNC₆H₃iPr₂-2,6)(MMe₃)}]₂ (Me=Al, Ga). Oxidation of the cerium(III) complex with hexachloroethane leads to a neutral Ce^IV diimide species. Partial protonolysis with phenylacetylene and hydrogenolysis via H₃SiPh give conclusive insights into the reactive coordination sites of such diimide complexes.