Primary Screens

If some other criterion such as creep-rupture strength is of primary importance, the alloy choice may be restricted. Here it would be necessary to have thennal fatigue comparisons only for the alloys that pass the primary screening. When alloy selection reaches this stage some further cautions are in order. 

Although a correlation between BET surface areas from 77 K nitrogen isotherms and methane uptake at 298 K and 3.5 MPa has been shown for many carbon adsorbents, [11, 20], deviations from this relationship have been observed [20]. However, as a primary screening process for possible carbonaceous adsorbents for natural gas, this remains a useful relationship. It should be noted that this correlation only seems to be applicable for active carbons. 

Following from the above, behavioral assays, which can be relatively simple and cost-effective, can be very useful as primary screens when testing chemicals for their neurotoxicity in the context of medical toxicology (see Dewar 1983, Atterwill et al. 1991, and Tilson 1993). Where disturbances of behavior are identified, subsequent more specific tests, including in vitro assays, may then be performed to establish... 

Iversen (1991) stresses the need for some in vivo testing for neurotoxicity and emphasizes the value of sensitive behavioral tests. Behavioral tests are described for mice and rats, which provide measures of mood, posture, CNS excitation, motor coordination, sedation, exploration, responsiveness, learning, and memory function. Such assays can function as primary screens for neurotoxicity before adopting a stepwise scheme of in vitro tests to discover more about the initial site of action of neurotoxic compounds. It is argued that the requirement for animal testing can be drastically reduced by adopting structured in vitro protocols such as these. 

The minimum activity that defines ACTIVES in a PRIMARY SCREEN. It is usually expressed as percentage of inhibition or stimulation. For example, a widely used hit threshold is 50%. 

The layout of samples and controls configured on a plate during an assay. For example, for a primary screen in 384-well plates, columns 1, 2, 23, and 24 are controls, and columns 3-22 are for individual test compounds, whereas for secondary screening, each row will contain a single compound at varying concentrations. 

A screen applied to confirm independently actives from the primary screen. A secondary screen may employ an assay that differs in type from the primary screen, e.g., biochemical assay vs cell based assay, or it may be of the same type with different readout. 

At the completion of a primary screening of a compound library, a collection of hits will be identified that meet or exceed the inhibition percentage cutoff for hit declaration (as described above). The next step is to ensure the validity of these primary screening results through a series of experimental procedures aimed at addressing two aspects of hit validation hit confirmation and hit verification. 

The term hit confirmation, as we define it, involves three components reproducibility, confirmation of chemical structure, and confirmation of chemical purity. Confirmation of hit reproducibility requires that the subset of library compounds designated as hits in the primary screen be identified, that samples of each of these be obtained from the library bank (a process often referred to as cherry picking ), and that these samples be retested, at least once but preferably multiple times, to determine if they reproducibly confer an inhibition percentage of the target enzyme... 

The amount of total lead in the blood can be measured to determine if exposure to lead has occurred. This test can tell if you have been recently exposed to lead. Lead can be measured lead in teeth or bones by X-ray techniques, but these methods are not widely available. These tests tell about long-term exposures to lead. Exposure to lead can be evaluated by measuring erythrocyte protoporphyrin (EP) in blood samples. EP is a part of red blood cells known to increase when the amount of lead in the blood is high. However, the EP level is not sensitive enough to identify children with elevated blood lead levels below about 25 micrograms per deciliter ( ig/dL). For this reason, the primary screening method is measurement of blood lead. For more information on tests to measure lead in the body, see Chapters 2 and 6. 

Kinases remain a highly pursued drug target for numerous therapeutic areas [95]. In addition to the primary screen, selectivity profiling of... 

Thirteen different chiral diol ligands were used (Scheme 25), leading to a catalyst library of 104 members.121 In a model reaction benzaldehyde (51), (R = Ph) was used as the carbonyl component, HPLC being used to ascertain the enantiopurity of (92). Initially 1 mol.% of catalyst was used. In the primary screening catalysts modified by L4, L5, L6, and L7 turned out to be excellent (77-96% ee yields 63-100%). Thereafter the catalyst loading of Lm/Ti/Lra (m, n = A-l) was decreased to 0.1 mol.%, but this led to only trace amounts of product. Finally, the solvent was... 

In order to determine whether compounds identified in the primary HTS screen are specific, a counterscreen is required to identify and eliminate false positives that will arise in the primary screen. For protein—protein interaction screens, it is preferable to test an unrelated protein pair that uses the same mode of detection. For our purposes, we adapted a previously described TR-FRET assay that monitors the interaction between bacterial Staphylococcus aureus Dnal and phage protein 77ORF104 (Liu et al., 2004). 

Preparation of Krebs-2 translation extracts Krebs-2 extracts are an ideal system to screen for compounds that inhibit translation because they faithfully recapitulate the cap dependency and the cap-poly(A) synergism associated with eukaryotic mRNA translation (Svitkin and Sonenberg, 2004), unlike standard rabbit reticulocyte lysates (RRL) (Borman et al., 2000). Furthermore, the translation of many types of IRESes is supported in Krebs-2 extracts. The use of commercially available translation competent extracts prepared from RRL, wheat germ, and E. coli is extremely useful in assessing selectivity of inhibitors identified in primary screens. 

Our screen has the potential to identify inhibitors of cap-dependent initiation, IRES-mediated initiation, and translation elongation or termination. One assay to identify initiation inhibitors from hits obtained in the primary screen is to assess the ability of a given compound to prevent 48S and/or 80S initiation complex formation on a capped mRNA and on the HCV IBJ3S. Because initiation complexes are formed more efficiently in RRL than in... 

Budantsev, A. Yu., and Litvinova, E.G. (1996). Test-paper for primary screening of pharmacological compounds possessing MAO-inhibitory activity. Experimental and Clinical Pharmacology (Russia) 59 68-70. 

The molecular weight distribution of a polymer produced with a chain shuttling catalyst/CSA system is highly dependent on reaction conditions. The extent of reversibility with the catalyst/CSA pairs was therefore further explored through a series of polymerizations over a range of monomer conversions (i.e., yield). A representative example from this secondary screening process is described below for precatalyst 17. Several members from this well-studied bis(phenoxyimine)-based catalyst family [39] were identified as poor incorporators in the primary screen. A series of ethylene/octene copolymerizations using 17 was performed across a... 

The involvement of several tyrosine kinases in various cancers requires efficient screening methodologies for the inhibitory compounds. Screening is divided into three steps (1) primary screening against the pure isolated PTK in a cell-free system. The objective is always an ELISA format. The compounds are screened against a battery of PTKs and Ser/Ther kinases in order that the pattern of selectivity can be established quickly [2]. 

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