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Valuable Starting Point (valuable + starting_point)
Selected AbstractsSynthesis and In Vitro Evaluation of 2-Aminoquinazolin-4(3H)-one-Based Inhibitors for tRNA-Guanine Transglycosylase (TGT)HELVETICA CHIMICA ACTA, Issue 6 2004Emmanuel tRNA-Guanine transglycosylase (TGT) plays a key role in the post-transcriptional modification of tRNA. It has been linked with the pathogenicity of shigellae, the causative agents of bacillary dysentery (shigellosis). Here, we report structureactivity relationships (SARs) for a new series of 2-aminoquinazolin-4(3H)-one-based inhibitors of TGT, resulting from structure-based design (Fig.,2). Versatile synthetic protocols allow selective functionalization of the 2-aminoquinazolin-4(3H)-one core (Schemes,1,6) with H-bond-donor groups in position 6 (for H-bonding to the C=O group of Leu231) and lipophilic residues in position 8 for reaching into a shallow, newly discovered lipophilic pocket lined by Val282, Val45, and Leu68. The binding mode of several of these ligands in the active site of TGT was established by crystal structure analyses (Figs.,4 and 6). A dramatic S effect was observed, with the replacement of the S-atom in the (phenylsulfanyl)methyl residue in position 8 of inhibitor 1c (Ki=100,nM) by the O-atom (in 1h, Ki=5.6,,M) or CH2 (in 1i, Ki=3.6,,M), resulting in a massive loss of activity (Fig.,3). Crystal structure analysis showed that the lipophilic Me group points into a highly polar region of the active site encompassed by the side chains of Asp280 and Asp102 and collides directly (d(C,,,O)=3.1,Å) with one of the O-atoms of the carboxylate of Asp102. Similarly, lipophilic linkers departing from position 8 and orienting residues in the shallow hydrophobic pocket presumably encounter analogous unfavorable contacts, accounting for the modest contribution to the binding free enthalpy upon introduction of these residues. These findings provide a valuable starting point for future structure-based lead optimization cycles leading to TGT inhibitors with increased in vitro potency. [source] Intra-seasonal rainfall characteristics and their importance to the seasonal prediction problemINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2002Warren J. Tennant Abstract Daily station rainfall data in South Africa from 1936 to 1999 are combined into homogeneous rainfall regions using Ward's clustering method. Various rainfall characteristics are calculated for the summer season, defined as December to February. These include seasonal rainfall total, region-average number of station rain days exceeding 1 and 20 mm, region-average of periods between rain days at stations >1 and >20 mm, region-average of wet spell length (sequential days of station rainfall >1 and >20 mm), correlation of daily station rainfall within a region and correlation of seasonal station rainfall anomalies within a region. Rank-ordered rainfall characteristic data generally form an s-shaped curve, and significance testing of discontinuities in these curves suggests that normal rainfall conditions in South Africa consist of a combined middle three quintiles separated from the outer quintiles, rather than the traditional middle tercile. The relationships between the various rainfall characteristics show that seasons with a high total rainfall generally have a higher number of heavy rain days (>20 mm) and not necessarily an increase in light rain days. The length of the period between rain days has a low correlation to season totals, demonstrating that seasons with a high total rainfall may still contain prolonged dry periods. These additional rainfall characteristics are important to end-users, and the analysis undertaken here offers a valuable starting point for seeking physical relationships between rainfall characteristics and the general circulation. Preliminary studies show that the vertical mean wind is related to rainfall characteristics in South Africa. Given that general circulation models capture this part of the circulation adequately, seasonal forecasts of rainfall characteristics become plausible. Copyright © 2002 Royal Meteorological Society. [source] Conservation goals and fisheries management units for Atlantic salmon in the Baltic Sea areaJOURNAL OF FISH BIOLOGY, Issue 2001M-L. Koljonen The effective application of genetic information in fisheries management strategies implies political goal setting taking both conservation and fisheries management into account. The concept of sustainable use as set out by the Convention on Biological Diversity offers a valuable starting point in this respect, since the criterion for it is defined as the maintenance of genetic diversity within each species. However, strategic decisions are also needed on the practical level, where the actual genetic information can be taken into account. Genetic factors, such as glacial differentiation, the postglacial genetic structure of populations, gene flow levels and the probability of the existence of adaptive differences, have an effect on the formation of conservation and management units and on the long-term strategy for the sustainable use of aspecies. The Atlantic salmon (Salmo salar) in the Baltic Sea area is treated here as an example of a complicated management problem with a highly hierarchical genetic structure associated with marked loss of naturally reproductive stocks, extensive hatchery production and an effective international offshore fishery. The implications of genetic factors for the conservation and management strategy of the Baltic salmon is discussed in the light of the goals set by the Convention on Biological Diversity, the Straddling Fish Stocks and Highly Migratory Fish Stocks Agreement, the Habitats Directive of the European Union and the International Baltic Sea Fishery Commission. [source] Development of a Method for the High-Throughput Quantification of Cellular ProteinsCHEMBIOCHEM, Issue 10 2009Paolo Paganetti Dr. Abstract Hunting for huntingtin: We describe a screening assay based on the inducible expression of the mutant huntingtin protein in cells and on its highly sensitive homogenous determination. Rapid, reproducible, and robust protein determination was achieved through the use of two donor,acceptor-labeled antibodies and time-resolved FRET. The assay was developed and validated for ultra-throughput screening of low-molecular-weight compounds modulating the expression of the mutant protein. The quantification of cellular proteins is essential for the study of many different biological processes. This study describes an assay for the detection of the intracellular mutant huntingtin, the causative agent of Huntington's disease, with a method that may be generally applicable to other cellular proteins. A small recombinant protein tag that is recognized by a pair of readily available, high-affinity monoclonal antibodies was designed. This tag was then added to an inducible fragment of the mutant huntingtin protein by genetic engineering. We show that it is possible to use time-resolved FRET to detect low intracellular levels of huntingtin by a simple lysis and detection procedure. This assay was then adapted into a homogeneous, miniaturized format suitable for screening in 1536-well plates. The use of time-resolved FRET also permits the assay to be multiplexed with a standard readout of cell toxicity, thus allowing the identification of conditions causing reduction of protein levels simply due to cytotoxicity. The screening results demonstrated that the assay is able to identify compounds that modulate the levels of huntingtin both positively and negatively and that represent valuable starting points for drug discovery programs. [source] | |||||||||||||