NMR-based functional assay

Key words Fragment-based drug design, Ligand-based NMR, Hit identification, STD, STDD, NMR-based functional assay... 

In this chapter we present the detailed setup of ligand-based NMR experiments and an NMR-based functional assay using a 30 kDa enzyme protein that makes bacteria resistant to a broad range of beta-lactam antibiotics. STD, c-STD, and STDD were used for fragment screening and an NMR-based functional assay that monitors the hydrolysis of ampicillin was used for functional validation of fragment hits with weak affinities/activities. 

We would like to thank Yan Hou and Mark McCoy for developing the ID proton NMR-based functional assay and Hugh Eaton and Corey Strickland for valuable discussions. 

Finally, substrate-based functional NMR assays can be used to derive the percentage inhibition or IC50 values [49]. In our experience, functional NMR assays can also reveal valuable details about the mode of action of modulators, since the... 

Another report demonstrates the capability of providing quantitative information on the extent of conversion of a solid-phase material. This method may be applicable to a wide range of reaction chemistries and resin-supported materials. These authors use NMR to quantify the extent of the derivatization of functionalized polymeric material with a fluorinated substrate. Thus the rate of the reaetion of Merrifield resin with 2-lluo-rophenol was examined. At various time intervals portions of the reacting resins were removed and were exhaustively reacted with excess 4-lluo-rophenol. Analysis of the resin samples shows two signals (Scheme 2.9), one for the 2-fluoro derivative at -134 ppm and the other for the 4-fluoro derivative at -124ppm. Quantitative information on the extent of the reaction was obtained by measuring the relative intensities of the resin bound fluorine and a known concentration of an internal standard in solution, such as fluorobenzene. It was noted that there needed to be a sufficient time delay between the RF pulses so that the solid-phase and solution-phase nuclei would be similarly relaxed in the F NMR spectra. This method provided excellent correlation for resin-bound F atom content in samples containing 30 mg resin samples blended to various extents with 100% 2-fluorophenyl Merrifield ether and unfunctionalized Merrifield resin. This fluorophenol based assay was then used to optimize the attaehment of an epoxide to the Merrifield resin (Scheme 2.10). The alkylation reaetion was monitored at... 

The semicontinuous surfactant-free synthesis of a core/shell styrene/acrolein latex and its analysis for surface aldehyde functions are described. A calorimetric assay based on reaction with dinitrophenylhydrazine is compared with reduction by tritiated sodium borohydride and integration of aldehyde peaks in the proton NMR spectrum of the dissolved polymer. X-ray photoelectron spectroscopy confirmed the surface location of the aldehyde functions and the analytical reaction products. The three assay procedures were in reasonable agreement, suggesting all the aldehyde functions were accessible to aqueous reagents. Relevance to protein carriers is indicated. 21 refs. CANADA... 

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