Protein phosphatases have very recently emerged as important targets for chemical biology and medicinal chemistry research, and new phosphatase inhibitor classes are in high demand. The underlying frameworks of natural products represent the evolutionarily selected fractions of chemical space explored by nature so far and meet the criteria of relevance to nature and biological prevalidation most crucial to inhibitor development. We refer to synthesis efforts and compound collection development based on these criteria as biology-oriented synthesis. For the discovery of phosphatase inhibitor classes by means of this approach, four natural product-derived or -inspired medium-sized compound collections were synthesized and investigated for inhibition of the tyrosine phosphatases VE-PTP, Shp-2, PTP1B, MptpA, and MptpB and the dual-specificity phosphatases Cdc25A and VHR. The screen yielded four unprecedented and selective phosphatase inhibitor classes for four phosphatases with high hit rates. For VE-PTP and MptpB the first inhibitors were discovered. These results demonstrate that biology-oriented synthesis is an efficient approach to the discovery of new compound classes for medicinal chemistry and chemical biology research that opens up new opportunities for the study of phosphatases, which may lead to the development of new drug candidates.chemical biology ͉ medicinal chemistry ͉ phosphatase inhibition P rotein phosphatases are key regulators of innumerable biological processes (1, 2). Small-molecule modulators of phosphatase activity have proven to be powerful tools for the study of the chemical biology of these enzymes (3), and, in particular, protein tyrosine phosphatases (PTPs) (4, 5) and dual-specificity phosphatases (6) have recently moved into the focus of a growing number of drug discovery programs, for instance in diabetes and anticancer research. However, although important progress has been made, the development of potent and selective phosphatase inhibitors is still in its early stages, and structurally new phosphatase inhibitor classes are in high demand.Relevance to nature is one of the most important criteria to be met by compound classes for chemical biology and medicinal chemistry research. The underlying frameworks of natural products (NPs) provide evolutionarily selected chemical structures encoding the properties required for binding to proteins, and their structural scaffolds represent the biologically relevant and prevalidated fractions of chemical space explored by nature so far (7-9). Consequently, it is to be expected that compound collections designed on the basis of NP structure will be enriched in biochemical and biological activity. Based on this reasoning, we have introduced a structural classification of natural products (SCONP) in a tree-like arrangement as an idea-and hypothesis-generating tool for the design and synthesis of compound collections (8). It permits the selection of library scaffolds based on relevance to and prevalidation by nature. We refer to synthesis efforts base...

The H ϩ -translocating ATPase of chloroplasts (CF 0 CF 1 , 1 chloroplast ATP synthase) is a latent enzyme. Its physiological activation requires a transmembrane electrochemical proton potential difference (1-4). Hence, the proton gradient in addition to its role as the driving force of phosphorylation is a factor that controls CF 0 CF 1 activity. The obvious physiological meaning of this control mechanism is the suppression of unproductive ATP hydrolysis under conditions that would energetically allow this reaction, i.e. at low proton gradients (low light or dark) and high phosphate potentials.A superimposed regulatory device is the so-called thiol modulation of CF 0 CF 1 . The structural basis for thiol modulation is a sequence motif of nine amino acids comprising two cysteines in the ␥ subunit of CF 1 (5). This segment is present in higher plants (6) and green algae (7) but not in cyanobacteria (8 -10) or in diatoms (11) suggesting that thiol modulation is an acquisition of the chlorophyll a ϩ b plants only. In the demodulated (oxidized) state the two cysteines form a disulfide bond whereas the modulated state is obtained by reduction of this disulfide bridge. In vitro reduction can be achieved by dithiothreitol or other dithiols, but the natural reductant is a reduced thioredoxin. In chloroplasts at least two different thioredoxins occur, thioredoxin-m (Tr-m) and thioredoxin-f (Tr-f) (12). The former is thought to be involved in light/dark regulation of the chloroplast NADP-specific malate dehydrogenase, and the latter is responsible for the light/dark regulation of fructose bisphosphatase and other Calvin cycle enzymes (13,14). The thioredoxins are reduced via ferredoxin and ferredoxin-thioredoxin reductase (15) by electrons from the photosynthetic electron transport chain. In most of the experiments carried out so far, however, thiol modulation of CF 0 CF 1 was conducted with the artificial reductant dithiothreitol, and in a few studies Escherichia coli thioredoxin (Trx) was used (16, 17). Little information is known about the action of the naturally occurring chloroplast thioredoxins on CF 0 CF 1 (18 -20).Thiol modulation requires illumination of the chloroplasts to allow reduction of the disulfide bridge. Apparently, the regulatory segment of the ␥ subunit, which is hidden in the dark, becomes accessible as a consequence of ⌬H ϩ -induced CF 0 CF 1 activation (16,21). Decay of the proton gradient in the dark leads to deactivation of the ATP synthase. The most significant difference between the reduced and oxidized active states concerns the velocity of deactivation. While the oxidized form is immediately deactivated upon relaxation of the gradient, deactivation of thiolmodulated CF 0 CF 1 takes several minutes. For this reason only chloroplasts with thiol-modulated CF 0 CF 1 are capable of hydrolyzing added ATP after transition from light to dark (22,23).Deactivation of the modulated enzyme may proceed with or without reoxidation of the dithiol group (16). Most likely the natural actual oxidant is the oxid...

In this paper the authors emphasise that the proton translocating ATP synthase from thiol-modulated chloroplasts and two cyanobaeterial strains has a coupling ratio of 4 protons per ATP synthesised or hydrolysed. This ratio is determined by several thermodynamic studies at equilibrium between phosphate potential (AGp) and proton gradient (zl/iu+), and is confirmed by measurement of proton flux during ATP hydrolysis. Ratios lower than 4 H+IATP that have been published in the past have predominantly been determined with the oxidised chloroplast enzyme. Errors in these measurements will be discussed.

A separation kernel simulates a distributed environment using a single physical machine by executing partitions in isolation and appropriately controlling communication among them. We present a formal verification of information flow security for a simple separation kernel for ARMv7. Previous work on information flow kernel security leaves communication to be handled by model-external means, and cannot be used to draw conclusions when there is explicit interaction between partitions. We propose a different approach where communication between partitions is made explicit and the information flow is analyzed in the presence of such a channel. Limiting the kernel functionality as much as meaningfully possible, we accomplish a detailed analysis and verification of the system, proving its correctness at the level of the ARMv7 assembly. As a sanity check we show how the security condition is reduced to noninterference in the special case where no communication takes place. The verification is done in HOL4 taking the Cambridge model of ARM as basis, transferring verification tasks on the actual assembly code to an adaptation of the BAP binary analysis tool developed at CMU.

Coexistence of tics and attention-deficit/hyperactivity disorder (ADHD) has important clinical and scientific implications. Existing data on the co-occurrence of tic disorders, Tourette Syndrome (TS), and ADHD are largely derived from small-scale studies in selected samples and therefore heterogeneous. The Nordbaden project captures the complete outpatient claims data of more than 2.2 million persons, representing 82% of the regional population in 2003. Based upon the number of diagnosed cases of tic disorders, TS, and ADHD, we determined 12-months administrative prevalence rates as well as rates of co-occurrence. Both tic disorders and ADHD were diagnosed most often in the age group 7-12 years (any tic disorder: 0.8%; ADHD: 5.0%). With increasing age, the administrative prevalence difference in favor of males disappeared, with tic disorders being somewhat more frequently reported in females than males in the age groups above 30 years. The highest rate of ADHD co-occurring with tic disorders was found in adolescents (age 13-18 years, 15.1%). Tic disorders were observed in 2.3% of patients with ADHD. Administrative prevalence rates of tic disorders and TS were substantially lower compared to rates found in community-based epidemiological studies, suggesting that a large number of cases remain undetected and untreated under present conditions of routine outpatient care.

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A natural product collection and natural-product-derived combinatorial libraries were virtually screened for potential inhibitors of human 5-lipoxygenase (5-LO) activity. We followed a sequential ligand-based approach in two steps. First, similarity searching with a topological pharmacophore descriptor (CATS 2D method) was performed to enable scaffold-hopping. Eighteen compounds were selected from a virtual hit list of 430 substances, which had mutual pharmacophore features with at least one of 43 known 5-LO inhibitors that served as query structures. Two new chemotypes exhibited significant activity in a cell-based 5-LO activity assay. The two most potent molecules served as seed structures for a second virtual screening round. This time, a focused natural-product-derived combinatorial library was analyzed by different ligand-based virtual screening methods. The best molecules from the final set of screening candidates potently suppressed 5-LO activity in intact cells and may represent a novel class of 5-LO inhibitors. The results demonstrate the potential of natural-product-derived screening libraries for hit and lead structure identification.