Use of SAM2 biotin capture membrane in microarrayed compound screening (muARCS) format for nucleic acid polymerization assays

Putting Thought to Paper: A μARCS Protease Screen

In micro-arrayed compound screening (μARCS), an agarose gel is used as a reaction vessel that maintains humidity and compound location as well as being a handling system for reagent addition. Two or more agarose gels may be used to bring test compounds, targets, and reagents together, relying on the pore size of the gel matrix to regulate diffusion of reactants. It is in the microenvironment of the agarose matrix that all the components of an enzymatic reaction interact and result in inhibitable catalytic activity. In an effort to increase the throughput of μARCS-based screens, reduce the effort involved in manipulating agarose gels, and reduce costs, blotter paper was used rather than a second agarose gel to introduce a substrate to a gel containing a target enzyme. In this assay, the matrix of the blotter paper did not prevent the substrate from diffusing into the enzyme gel. The compound density of the μARCS format, the ease of manipulating sheets of paper for reagent addition, and a scheduled protocol for running multiple gels allowed for a throughput capacity of more than 200,000 tests per hour. A protease assay was developed and run in the μARCS format at a rate of 200,000 tests per hour using blotter paper to introduce the substrate. Picks in the primary screen were retested in the μARCS format at a density of 384 compounds per sheet. IC50values were confirmed in a 96-well plate format. The screen identified several small molecule inhibitors of the enzyme. The details of the screening format and the analysis of the hits from the screen are presented.

Recent Advances in Technologies for Analyzing Protein Kinases

Most cellular events are regulated by protein phosphorylation mediated by protein kinases, whose malfunction is involved in the etiology of various disorders. The elucidation of the biochemical properties of the protein phosphorylation reaction will lead not only to a better understanding of the signal transduction mechanism, but also to developing new therapeutic agents. In this review, we briefly summarize the technologies to detect or characterize protein kinases with special emphasis on recently developed and/or commercially available techniques.

Compound transfer efficiency from polystyrene surfaces: application to microarrayed compound screening

In microarrayed compound screening (microARCS), compounds are spotted and dried onto a polystyrene sheet (ChemCard)ata high density and introduced into the assay by contacting with agarose gels that contain reagents for the assay. The authors have conducted studies to characterize the compound transfer process using 59 compounds of diverse properties. The amount of compounds remaining on the ChemCard was determined by liquid chromatography/mass spectrometry after incubation with agarose gels for predetermined time periods. The results showed good correlation with kinetics of compound transfer to phosphate-buffered saline (PBS) buffer, but only moderate correlation with equilibrium solubility of compounds in PBS buffer. These observations indicate that the major factor determining compound transfer efficiency is the kinetics of dissolution of compounds, rather than equilibrium solubility and diffusion of compounds in the gel. Compounds of lower ClogP showed a higher rate of transfer to agarose gels and vice versa. Other compound properties such as molecular weight, size, acid-base, and H-bonding properties did not significantly affect compound transfer. Importantly, the majority of the compounds studied show greater than 20% transfer after a 10-min incubation with agarose gels, providing sufficient amounts of compounds for screening purposes.

The evolution of microarrayed compound screening

This review describes recent developments in the evolutionary process of microarrayed compound screening (microARCS to become a robust and efficient ultra-high-throughput screening technology. Improvements in compound spotting (including new quality-control methods), gel casting and imaging, together with software capable of automatic analysis and deconvolution of images, have helped to streamline the screening process. A variety of screening projects using cell-based and non-cell-based approaches have been successfully concluded using microARCS. Comparison of hits derived from standard microtitre-plate-based screening and from microARCS reveals excellent overlap. Furthermore, there seems to be no bias towards finding compounds within a particular range of logP values, even though compounds are solubilized from a dry state during the course of the assay.