Coherent and incoherent magnetization transfer in the rotating frame

Abstract

Two-dimensional (2D) NMR spectroscopy has become a routine part of molecular structure determination in liquids. In most modern experiments there is some correlation of transition frequencies between the two dimensions, and the mechanism responsible for the correlation dictates the information obtainable from the 2D spectrum. Two distinct mechanisms for magnetization transfer are considered : scalar coupling and cross-relaxation. The former gives rise to information about the proximity of spins through the electronic framework of the molecule and the latter provides information on spatial proximity and molecular motion. Two-dimensional experiments of both types are described, concentrating in particular on TOCSY and ROESY. It is shown how polarization transfer can be tailored and controlled, and how the unwanted coherent transfer due to J coupling can he eliminated in the ROESY experiment. Throughout the discussion, the multiple-pulse sequence used for each experiment is the central focal point, and its design and analysis are the main considerations.

Structural and Folding Dynamic Properties of the T70N Variant of Human Lysozyme

“…Selective one-dimensional NOESY experiments for temperature coefficient measurements were run by replacing the first two 90°pulses of the standard sequence with selective Gaussian-shaped pulses of 6 ms centered on the side-chain amide resonance of interest. The water resonance was suppressed by appending an excitation-sculpting module (16) to the nonselective detection pulse. The acquisitions were performed between 33 and 40°C by collecting 512 scans over 2 13 data points to monitor the chemical shift of the exchanging, unperturbed side-chain-amide resonance with sufficient precision (⌬␦ ϭ Ϯ 0.8 ppb).…”

Phenylpropanoid Glycosides from Rhodiola rosea.

“…Typically a 0.4-0.8 s acquisition time with 2 s relaxation delay was used for 1 H experiments, with or without water suppression that was performed by excitation sculpting method by Hwang and Shaka. 21) For TOCSY and COSY experiments a 0.4 s acquisition times and 1.6 s relaxation delays were used together with 128 or 256 increments and varying number of experiments. Mixing time used for TOCSY were 120-160 ms. For HSQC-DEPT and HMBC experiments 128 increments and varying number of experiments were acquired with 0.5 s acquisition times and 1.4 s relaxation delays, optimizing J CH couplings for 145 Hz and 4-10 Hz, respectively.…”

Encapsulation of Triphenylene Derivatives in the Hexanuclear Arene Ruthenium Metallo‐Prismatic Cage [Ru6(p‐PriC6H4Me)6(tpt)2(dhbq)3]6+ (tpt = 2,4,6‐tri(pyridin‐4‐yl)‐1,3,5‐triazine, dhbq = 2,5‐dihydroxy‐1,4‐benzoquinonato)

“…The 1-D 1 H ROESY experiments have been recorded using the MP-ROESY mixing sequence, which has shown its effectiveness with regard to TOCSY transfer suppression and cross-relaxation peak intensity enhancement [7]. The mixing time of the experiments has been kept short (100ms) to avoid spin diffusion and so that the linear approximation remains valid [8].…”