Random phase detection in multidimensional NMR

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 40; pp. 16640 - 16644
• Main Authors: Maciejewski, Mark W., Fenwick, Matthew, Schuyler, Adam D., Stern, Alan S., Gorbatyuk, Vitaliy, Hoch, Jeffrey C.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 04.10.2011; National Acad Sciences
• Subjects: Ambiguity; Biological Sciences; Data sampling; Datasets; Entropy; Fourier transformations; Historic artifacts; Image Processing, Computer-Assisted; Magnetic Resonance Imaging - methods; Magnetic Resonance Spectroscopy - methods; NMR; Nuclear magnetic resonance; Receivers & amplifiers; Resonance; Signaling; Sine waves; Spectral reconnaissance; Spectroscopy; Time Factors
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1103723108

Despite advances in resolution accompanying the development of high-field superconducting magnets, biomolecular applications of NMR require multiple dimensions in order to resolve individual resonances, and the achievable resolution is typically limited by practical constraints on measuring time. In addition to the need for measuring long evolution times to obtain high resolution, the need to distinguish the sign of the frequency constrains the ability to shorten measuring times. Sign discrimination is typically accomplished by sampling the signal with two different receiver phases or by selecting a reference frequency outside the range of frequencies spanned by the signal and then sampling at a higher rate. In the para metrically sampled (indirect) time dimensions of multidimensional NMR experiments, either method imposes an additional factor of 2 sampling burden for each dimension. We demonstrate that by using a single detector phase at each time sample point, but randomly altering the phase for different points, the sign ambiguity that attends fixed single-phase detection is resolved. Random phase detection enables a reduction in experiment time by a factor of 2 for each indirect dimension, amounting to a factor of 8 for a four-dimensional experiment, albeit at the cost of introducing sampling artifacts. Alternatively, for fixed measuring time, random phase detection can be used to double resolution in each indirect dimension. Random phase detection is complementary to nonuniform sampling methods, and their combination offers the potential for additional benefits. In addition to applications in biomolecular NMR, random phase detection could be useful in magnetic resonance imaging and other signal processing contexts.