Affinity NMR.

Because binding ligands are directly detected and identified, the diffusion-based NMR method and NOE pumping approach promise to greatly simplify deconvolution in drug screening. An additional advantage of these techniques is that low-affinity ligands, which might be missed by high-throughput screening, can be detected and could serve as synthetic precursors for higher affinity ligands. The biggest challenge to NMR methodology lies in its sensitivity. Compared with other techniques, such as MS (25), NMR methods for screening mixtures are limited by their relative insensitivity. Because of issues such as solubility, stability, and mass limitation, it is not in general judicious to simply increase the concentration of the mixture. Improvements in hardware and software are necessary to extend the applicability of the affinity NMR method to the screening of larger and more complex mixtures. A boost in sensitivity and screening capacity of NMR technique is possible by the implementation of microcoil (26) and flow probe techniques. An upsurge in the capabilities of mixture analysis could be achieved with a combination of independent and complementary techniques (e.g., HPLC, MS) (27). As a unique, nondestructive, and versatile tool, NMR will continue on its fast track of development in the support of drug discovery.