Direct-Injection NMR (DI-NMR):  A Flow NMR Technique for the Analysis of Combinatorial Chemistry Libraries

Abstract

A new tool for analyzing compound libraries by NMR has been developed. Aliquots of solution-state samples (between 120 and 350 microL) are directly injected, using a standard liquids handler, into an NMR (LC-NMR) flow probe. Automated NMR software tracks--and suppresses--intense signals arising from the nondeuterated solvents used (if any) and acquires high-sensitivity one-dimensional 1H NMR spectra. An 88-member combinatorial library, dissolved in DMSO and stored in a 96-well microtiter plate, has been analyzed a number of ways using this technique. This nondestructive technique, which we call direct-injection NMR (DI-NMR) and which is embodied in our versatile automated sample changer (VAST) hardware, has proven to be both routine and robust. Our success in automatically acquiring the NMR data for entire plates of library compounds (within 4-8 h) has caused us to develop new ways to display and analyze the resulting NMR data, as will be shown here.

Flow injection analysis NMR (FIA–NMR): a novel flow NMR technique that complements LC–NMR and direct injection NMR (DI–NMR)

“…The Gilson 215 Liquids Handler uses a needle and a bidirectional syringe pump to transfer sample solutions from their original containers to an injector port. 18 The injector port is connected directly to the NMR flow probe with 1-3 ms of capillary tubing. The sample plug is delivered intact and unmodified into the flow probe.…”

“…16 -18 We have also made one implementation of DI-NMR commercially available as a product called VAST, the Versatile Automated Sample Transport sample changer. 18 Like LC-NMR, it uses an NMR flow probe, but its fluid-flow path, its typical analysis time and its applications are significantly different to those of LC-NMR.…”

“…This capability has been applied to the analysis of pure-compound combinatorial chemistry libraries (by the acquisition of 1D 1 H NMR spectra) 18,19 and biofluids, 20 and also the analysis of SAR-by-NMR libraries by the acquisition of 2D 1 Hf 15 Ng HSQC data. 21 Sample injection and NMR measurement times are usually under 5 min each per sample, so DI-NMR analysis times are usually much shorter than those used in LC-NMR.…”

Analysis and screening of combinatorial libraries using mass spectrometry

“…The main impediments of applying LC-NMR-MS to combinatorial chemistry remain poor sensitivity of the NMR, the obligatory use of deuterated solvents for chromatography, and the low throughput of NMR analyses. However, efforts are in progress to improve the throughput of NMR analyses [72][73][74].…”

Fast identification of flavonoids in the roots of Sophora flavescens by on-flow LC-NMR

“…Two modes, on-flow and stop-flow, are available in the LC-NMR. In general, on-flow mode is used to screen for the presence of particular groups of compounds or to gain a general overview in the mixture while stop-flow mode is chosen to acquire more exact information including two-dimensional NMR spectra such as COSY, HMBC and HSQC (Keifer et al, 2000;Elipe et al, 2010).…”