Inhibition of Acetylcholinesterase by N-Alkylpyridinium and N-Alkylpyridinium-2-aldoxime Salts

The interaction of a series of N-a1kylpyridinium and N-alkylpyridinium- 2-aldoxime salts with bovine erythrocyte acetylcholinesterase was investigated for inhibition of the hydrolysis of the substrates acetylcholine and dimethylaminoethyl acetate. The compounds cause a mixed inhibition of the acetylcholine hydrolysis which is interpreted as an interaction with the free enzyme (competitive component) and with the acetylenzyme (non- competitive component). The results suggest that the compounds have a higher affinity for the free enzyme than for the acetyl- enzyme. Enlargement of the alkyl-group increases the binding capacity to the free enzyme. The aldoxime group hardly effects the binding to the free enzyme, but tends to increase the binding to the acetyl-enzyme. Some results obtained with dimethylaminoethyl acetate support the mechanism of inhibition as proposed from acetylcholine hydrolysis inhibition. In contrast to this mechanism some compounds do not influence or even increase the maximum velocity of the dimethylaminoethyl acetate hydrolysis. It is suggested that a ternary complex of enzyme, substrate and pyridinium compound may be formed from which, in case of dimethylaminoethyl acetate, the enzyme is more rapidly acetylated

Inhibition of Acetylcholinesterase by N-Alkylpyridinium and N-Alkylpyridinium-2-aldoxime Salts

The interaction of a series of N-a1kylpyridinium and N-alkylpyridinium- 2-aldoxime salts with bovine erythrocyte acetylcholinesterase was investigated for inhibition of the hydrolysis of the substrates acetylcholine and dimethylaminoethyl acetate. The compounds cause a mixed inhibition of the acetylcholine hydrolysis which is interpreted as an interaction with the free enzyme (competitive component) and with the acetylenzyme (non- competitive component). The results suggest that the compounds have a higher affinity for the free enzyme than for the acetyl- enzyme. Enlargement of the alkyl-group increases the binding capacity to the free enzyme. The aldoxime group hardly effects the binding to the free enzyme, but tends to increase the binding to the acetyl-enzyme. Some results obtained with dimethylaminoethyl acetate support the mechanism of inhibition as proposed from acetylcholine hydrolysis inhibition. In contrast to this mechanism some compounds do not influence or even increase the maximum velocity of the dimethylaminoethyl acetate hydrolysis. It is suggested that a ternary complex of enzyme, substrate and pyridinium compound may be formed from which, in case of dimethylaminoethyl acetate, the enzyme is more rapidly acetylated

Sharing digital object across data infrastructures using Named Data Networking (NDN)

Data infrastructures manage the life cycle of digital assets and allow users to efficiently discover them. To improve the Findability, Accessibility, Interoperability and Re-usability (FAIRness) of digital assets, a data infrastructure needs to provide digital assets with not only rich meta information and semantics contexts information but also globally resolvable identifiers. The Persistent Identifiers (PIDs), like Digital Object Identifier (DOI) are often used by data publishers and infrastructures. The traditional IP network and client-server model can potentially cause congestion and delays when many consumers simultaneously access data. In contrast, Information-Centric Networking (ICN) technologies such as Named Data Networking (NDN) adopt a data-centric approach where digital data objects, once requested, may be stored on intermediate hops in the network. Consecutive requests for that unique digital object are then made available by these intermediate hops (caching). This approach distributes traffic load more efficient and reliable compared to host-to-host connection-oriented techniques and demonstrates attractive opportunities for sharing digital objects across distributed networks. However, such an approach also faces several challenges. It requires not only an effective translation between the different naming schemas among PIDs and NDN, in particular for supporting PIDs from different publishers or repositories. Moreover, the planning and configuration of an ICN environment for distributed infrastructures are lacking an automated solution. To bridge the gap, we propose an ICN planning service with specific consideration of interoperability across PID schemas in the Cloud environment

Ubiquitin-based probes prepared by total synthesis to profile the activity of deubiquitinating enzymes

Epitope-tagged active-site-directed probes are widely used to visualize the activity of deubiquitinases (DUBs) in cell extracts, to investigate the specificity and potency of small-molecule DUB inhibitors, and to isolate and identify DUBs by mass spectrometry. With DUBs arising as novel potential drug targets, probes are required that can be produced in sufficient amounts and to meet the specific needs of a given experiment. The established method for the generation of DUB probes makes use of labor-intensive intein-based methods that have inherent limitations concerning the incorporation of unnatural amino acids and the amount of material that can be obtained. Here, we describe the total chemical synthesis of active-site-directed probes and their application to activity-based profiling and identification of functional DUBs. This synthetic methodology allowed the easy incorporation of desired tags for specific applications, for example, fluorescent reporters, handles for immunoprecipitation or affinity pull-down, and cleavable linkers. Additionally, the synthetic method can be scaled up to provide significant amounts of probe. Fluorescent ubiquitin probes allowed faster, in-gel detection of active DUBs, as compared to (immuno)blotting procedures. A biotinylated probe holding a photocleavable linker enabled the affinity pull-down and subsequent mild, photorelease of DUBs. Also, DUB activity levels were monitored in response to overexpression or knockdown, and to inhibition by small molecules. Furthermore, fluorescent probes revealed differential DUB activity profiles in a panel of lung and prostate cancer cells

The spliceosome-activating complex: molecular mechanisms underlying the function of a pleiotropic regulator

Correct interpretation of the coding capacity of RNA polymerase II transcribed eukaryotic genes is determined by the recognition and removal of intronic sequences of pre-mRNAs by the spliceosome. Our current knowledge on dynamic assembly and subunit interactions of the spliceosome mostly derived from the characterization of yeast, Drosophila, and human spliceosomal complexes formed on model pre-mRNA templates in cell extracts. In addition to sequential structural rearrangements catalyzed by ATP-dependent DExH/D-box RNA helicases, catalytic activation of the spliceosome is critically dependent on its association with the NineTeen Complex (NTC) named after its core E3 ubiquitin ligase subunit PRP19. NTC, isolated recently from Arabidopsis, occurs in a complex with the essential RNA helicase and GTPase subunits of the U5 small nuclear RNA particle that are required for both transesterification reactions of splicing. A compilation of mass spectrometry data available on the composition of NTC and spliceosome complexes purified from different organisms indicates that about half of their conserved homologs are encoded by duplicated genes in Arabidopsis. Thus, while mutations of single genes encoding essential spliceosome and NTC components lead to cell death in other organisms, differential regulation of some of their functionally redundant Arabidopsis homologs permits the isolation of partial loss of function mutations. Non-lethal pleiotropic defects of these mutations provide a unique means for studying the roles of NTC in co-transcriptional assembly of the spliceosome and its crosstalk with DNA repair and cell death signaling pathways

Instruments of value: using the analytic tools of public value theory in teaching and practice

The tools of public value management - such as the strategic triangle and the public value account,– are increasingly used by scholars and practitioners alike. At the same time, some confusion remains regarding their functionality in action. Based on our experiences with these tools in classrooms and boardrooms, we analyze how these instruments help to explore and structure different dimensions of public management challenges. We propose a set of ‘principles of application’, detailing under what conditions public value tools are most likely to be helpful, and suggest a course of action for strengthening, connecting and extending the current tool box

Star formation in disk galaxies driven by primordial H_2

We show that gaseous \HI disks of primordial composition irradiated by an external radiation field can develop a multiphase medium with temperatures between 10^2 and 10^4 K due to the formation of molecular hydrogen. For a given \HI column density there is a critical value of the radiation field below which only the cold \HI phase can exist. Due to a time decreasing quasar background, the gas starts cooling slowly after recombination until the lowest stable temperature in the warm phase is reached at a critical redshift $z=z_{cr}$. Below this redshift the formation of molecular hydrogen promotes a rapid transition towards the cold \HI phase. We find that disks of protogalaxies with 10^{20}\simlt N_{HI}\simlt 10^{21} cm^{-2} are gravitationally stable at $T\sim 10^4$ K and can start their star formation history only at z \simlt z_{cr}\sim 2, after the gas in the central portion of the disk has cooled to temperatures T\simlt 300 K. Such a delayed starbust phase in galaxies of low gas surface density and low dynamical mass can disrupt the disks and cause them to fade away. These objects could contribute significantly to the faint blue galaxy population.Comment: 16 pages (LaTeX), 2 Figures to be published in Astrophysical Journal Letter

Quasiparticle energy spectrum in ferromagnetic Josephson weak links

The quasiparticles energy spectrum in clean ferromagnetic weak links between conventional superconductors is calculated. Large peaks in DOS, due to a special case of Andreev reflection at the ferromagnetic barrier, correspond to spin-splitt bound states. Their energies are obtained as a function of the barrier thickness, exchange field strength, and of the macroscopic phase difference $\phi$ at the link, related to the Josephson current. In the ground state, $\phi$ can be 0 or $\pi$, depending on the ferromagnetic barrier influence. Conditions for the appearence of the zero-energy bound states (ZES) and for the spin polarized ground state (SPGS) are obtained analytically. It is shown that ZES appear only outside the weak link ground state.Comment: 11 pages, 6 figure

A new mass-ratio for the X-ray Binary X2127+119 in M15?

The luminous low-mass X-ray binary X2127+119 in the core of the globular cluster M15 (NGC 7078), which has an orbital period of 17 hours, has long been assumed to contain a donor star evolving off the main sequence, with a mass of 0.8 solar masses (the main-sequence turn-off mass for M15). We present orbital-phase-resolved spectroscopy of X2127+119 in the H-alpha and He I 6678 spectral region, obtained with the Hubble Space Telescope. We show that these data are incompatible with the assumed masses of X2127+119's component stars. The continuum eclipse is too shallow, indicating that much of the accretion disc remains visible during eclipse, and therefore that the size of the donor star relative to the disc is much smaller in this high-inclination system than the assumed mass-ratio allows. Furthermore, the flux of X2127+119's He I 6678 emission, which has a velocity that implies an association with the stream-disc impact region, remains unchanged through eclipse, implying that material from the impact region is always visible. This should not be possible if the previously-assumed mass ratio is correct. In addition, we do not detect any spectral features from the donor star, which is unexpected for a 0.8 solar-mass sub-giant in a system with a 17-hour period.Comment: 6 pages, 4 figures, accepted by A&