NMR probes pCoil

Perhaps one of the first papers to be published demonstrating the application of pCoil NMR probe capabilities for dealing with the characterization of very small samples is to be found in the report by Subramanian et al 22 in 1999. The authors demonstrated the acquisition of HSQC data which < 100 nmol samples of several small molecules. For example, a very usable HSQC spectrum for a 13 pg sample of chloroquine (40 nmol) was acquired in 3.6 h. The authors also showed an HMQC spectrum recorded for a 27 pg sample of progesterone in 1.9 h. The latter spectrum, while certainly usable, could be improved by acquiring HSQC rather than HMQC data, and by increasing the number of files used to digitize the second frequency domain to improve Fi resolution. 

Sweedler et al.224 have exploited the mass sensitivity of pCoil NMR probes in the development of micromixer-based time-resolved NMR, demonstrating the application of the method to the conformation of the protein ubiquitin. To probe changes in protein conformation based on the elapsed time after a change in solvent composition, two capillary flows are mixed rapidly followed by the acquisition of... 

NMR spectra of the combined flows as a function of the time following mixing using a pCoil NMR probe. This approach allows the acquisition of time-dependent protein conformational data that would be difficult to acquire by other means. While limited to the acquisition of 11 spectral data for obvious reasons, the method still has interesting potential. 

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