Chemical probes development

Chemical Probe Development Versus Drug Development... 

This chapter provides a brief outline of the two major processes that have resulted in the existing armament of chemical modulators of protein phosphatases, namely, chemical probe development and drug development. These two processes initially seem to be rather similar and while they do overlap, the stated goals of the two approaches at project initiation are distinct. 

Key words Phosphatases, Chemical probe development. Drug development. Automated assays. 

It is only in the past 5 years or so that chemical probe development has really taken off. This has largely been driven by the NIH roadmap initiative which engaged a network (Molecnlar Libraries Probe Production Centers Network http //mli.nih.gov/mli/ mlpcn/mlpcn/) of academic-based centers that provided state-of-the-art high-throughput screening (HTS) capabilities of a large diverse small-molecule library (the Molecular Libraries Small Molecule Repository (MLSMR) >350,000 compounds) as well as much expertise in the activities of assay development and downstream hit to probe (http //mli.nih.gov/mli/). Prior to this initiative, HTS was almost exclusively conducted within pharmacentical... 

The power of the pooled GST fusion protein approach will increase as new biochemical reagents and assays become available. The development of chemical probes for biological processes, termed chemical biology, is a rapidly advancing field. For example, the chemical synthesis of an active site directed probe for identification of members of the serine hydrolase enzyme family has recently been described (Liu et al., 1999). The activity of the probe is based on the potent and irreversible inhibition of serine hydrolases by fluorophosphate (FP) derivatives such as diisopropyl fluorophosphate. The probe consists of a biotinylated long-chain fluorophosphonate, called FP-biotin (Liu et al., 1999). The FP-biotin was tested on crude tissue extracts from various organs of the rat. These experiments showed that the reagent can react with numerous serine hydrolases in crude extracts and can detect enzymes at subnanomolar... 

With this evidence of disease relevance, discovering and developing high-quality chemical probes [23] of PMTs has been gaining momentum in both the academic research community and the pharmaceutical industry. Progress in this area is keenly awaited. 

Each screening center has medicinal and synthetic chemistry expertise in order to optimize hits identified from HTS campaigns and develop them into chemical probes. Specific capabilities vary, however typical strategies employed include parallel synthesis, computational and informatics analysis, and analytical capabilities such as LC/MS techniques. The structures of novel compounds that are prepared, their synthetic protocols, analytical data and biological data are all available, and samples of final probes developed are deposited into the MLSMR. A Working Group comprised of chemists from each center meets regularly to share information, best practices, and insure optimal use of resources. 

The structure of a reacting molecule can be used as the chemical probe for the reaction mechanism in several ways. Ample experience is available with these methods from the research of noncatalytic homogeneous reactions, and their possibilities and limitations are well known. However, the solid catalyst restricts the scope to some extent on the one hand, but opens new applications on the other. For this reason, the methods of physical organic and inorganic chemistry developed for noncatalytic reactions cannot simply be transferred into the field of heterogeneous catalysis. The following remarks should identify some of the problems. 

The present chapter will primarily focus on oxidation reactions over supported vanadia catalysts because of the widespread applications of these interesting catalytic materials.5 6,22 24 Although this article is limited to well-defined supported vanadia catalysts, the supported vanadia catalysts are model catalyst systems that are also representative of other supported metal oxide catalysts employed in oxidation reactions (e.g., Mo, Cr, Re, etc.).25 26 The key chemical probe reaction to be employed in this chapter will be methanol oxidation to formaldehyde, but other oxidation reactions will also be discussed (methane oxidation to formaldehyde, propane oxidation to propylene, butane oxidation to maleic anhydride, CO oxidation to C02, S02 oxidation to S03 and the selective catalytic reduction of NOx with NH3 to N2 and H20). This chapter will combine the molecular structural and reactivity information of well-defined supported vanadia catalysts in order to develop the molecular structure-reactivity relationships for these oxidation catalysts. The molecular structure-reactivity relationships represent the molecular ingredients required for the molecular engineering of supported metal oxide catalysts. 

The aromatic nature of the presently discussed carbocations and dications have been further established by subjecting their NMR parameters to charge density chemical shift relationship449,475 77 originally developed by Spiesecke and Schneider.478,479 Furthermore, NICS (nucleus-independent chemical shift) developed by Schleyer et al.480 offers a simple and efficient probe for aromaticity. 

Figure 7.2.2 Schematic diagram of the flow probe developed by Dorn and co-workers and used for the direct coupling of SFC to NMR (a) insulated glass transfer line (b) glass insert (c) Cu/constantin thermocouple (d) stainless steel equilibrium coil (e) brass shield (f) Helmholtz coil (g) ceramic flow cell (h) brass Swagelok fitting. Reprinted with permission from Allen, L. A., Glass, T. E. and Dorn, H. C., Anal. Chem., 60, 390-394 (1988). Copyright (1988) American Chemical Society...

Second, we shall present our approach as to how to probe the palladium surfaces in more complex Pd/support catalysts, especially when the so-called metal-support interactions are expected. We shall develop our idea of how to use such chemical probes as a catalytic reaction (alkane catalytic conversion) or chemisorption in order to see important changes in the catalytic behavior. When possible, an adequate reference to available data from more sophisticated physical techniques is made. 

In searching for a relationship between antijuvenile hormone activities and epoxide chemical reactivity, we attempted to apply as a chemical probe the m-chloroperoxybenzoic-alkaline fluoride system, a reagent developed in this laboratory for preparation of acid labile epoxides (20). However, formation of hemiesters of 3,4-dihydroxy precocene, was the predominant reaction in the case of activated chro-mene structures. 

Although the development of high-throughput methods for producing natural product-inspired chemical probes is at an early stage, significant progress has been... 

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