Non Uniform Sampling (NUS) of multidimensional NMR data can greatly reduce the time taken to record a spectrum by recording only a subset of the normal data. A variety of algorithms are available to reconstruct the omitted data based on the data that was recorded. The most commonly used algorithm is Iterative Soft Thresholding (IST). Most implementations of the IST algorithm rely on the peaks in the detected dimension being phased correctly and positive. For most modern experiments this is not a problem, but in the HMBC experiment it is not possible to phase the peaks. For this reason I have not recommended using NUS with HMBCs. The LR-HSQMBC experiment, however, can be phased and I recommend using NUS with it. In this post, spectra recorded with different levels of NUS were recorded to determine how NUS affects HMBC and LR-HSQMBC experiments.
