Multiple-quantum J-resolved NMR spectroscopy (MQ-JRES): measurement of multiple-quantum relaxation rates and relative signs of spin coupling constants.
The technique of multiple-quantum J-resolved NMR spectroscopy (MQ-JRES) is introduced and applied to the spin system SI(3)-M (such as in the example given here, the (13)CH(3)-(12)CH in alanine). The SI(3) spin system was excited to its highest quantum state (8S(y)I(x)I(y)I(y)), which consists of four coherences: quadruple quantum of (3I + S), double quantum of (3I - S), double quantum of (I + S), and zero quantum of (I - S). In the MQ spectrum generated from the projection onto the F(1) dimension, the resonances of the different multiple-quantum coherences are resolved by their coupling constants to the remote spin (M). The absorptive lineshapes in both F(1) and F(2) dimensions enable accurate measurements of transverse relaxation rates, and both amplitude and relative signs of the long-range coupling constants are to be derived from either frequency or time domain data. The selective detection of MQ-JRES spectra of the individual MQ coherences using either phase cycling or pulsed field gradients is presented.
Liu
M
M
Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Wuhan, 430071, People's Republic of China. ml.liu@nmr.whcnc.ac.cn
Zhang
X
X
D000409:Alanine / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*
D011506:Proteins; D000409:Alanine