High concentration screening

High-concentration screening (HCS) assays tend to be used less frequently than biophysical methods, but can be employed to good effect due to their high-throughput capacity. These assays require biochemical function of the protein, up front knowledge of biochemical activity, and it can be difficult to reliably detect weak binders in the millimolar range. Fluorescence correlation... 

ChemBridge Fragment Set Low MW (< 300), and cLogP(< 3) designed for high aqueous solubility ( 3mM). 5000 Useful for high concentration screening (e.g., NMR/SPR-based approaches). 16... 

The first simulation studies of full double layers with molecular models of ions and solvent were performed by Philpott and coworkers [51,54,158] for the NaCl solution, using the fast multipole method for the calculation of Coulomb interactions. The authors studied the screening of a negative surface charge by free ions in several highly concentrated NaCl solutions. A combination of (9-3) LJ potential and image charges was used to describe the metal surface. 

Specific ion electrodes, similar in design to the glass electrode, have been developed to analyze for a variety of cations and anions. One of the first to be used extensively was a fluoride ion electrode that is sensitive to F- at concentrations as low as 0.1 part per million and hence is ideal for monitoring fluoridated water supplies. An electrode that is specific for Cl- ions is used to diagnose cystic fibrosis. Attached directly to the skin, it detects the abnormally high concentrations of sodium chloride in sweat that are a characteristic symptom of this disorder. Diagnoses that used to require an hour or more can now be carried out in a few minutes as a result, large numbers of children can be screened rapidly and routinely. 

FIGURE 8.15 Confirmation of initial hits in the HTS. Top panel shows the distribution of values from a single test concentration of a high-throughput screen. The criteria for activity and subsequent retest is all values >3 standard error units away from the mean (dotted line). The process of retesting will generate another distribution of values, half of which will be below the original criteria for activity. 

The use of direct UV spectrophotometry to measure sample concentrations in pharmaceutical research is uncommon, presumably because of the prevalence and attractiveness of HPLC and LC/MS methods. Consequently, most researchers are unfamiliar with how useful direct UV can be. The UV method is much faster than the other methods, and this is very important in high-throughput screening. 

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