Selective multiplet acquisition

N single quantum coherence. The chemical shift of 15N is recorded in a (semi-)constant-time manner during t2 and ultimately the 15N-1Hn PEP-TROSY element selects the most slowly relaxing 15N Hn multiplet component prior the acquisition. The coherence flow can thus be described as... 

Alternatively, ID analogues of 2D HSQC, HSQC-TOCSY, and HETLOC experiments and a selective version of/ -resolved spectroscopy using selective excitation and/or chemical shift filtering of proton or carbon resonances may be used for the measurement of coupling constants 49,51-59 Band-selective decoupling of some of the protons during acquisition leads to reduced multiplicity, and so facilitates the multiplet analysis.56... 

Figure 7.18. Traces from the 2D absorption-mode 7-resolved spectrum of menthol 7.1. (a) A region from the ID proton spectrum, (b) the 02 projection of the titled 2D spectrum showing proton-decoupled resonances and (c) the corresponding traces through the/i multiplets in the 2D spectrum. The multiplets for protons 3 and 4 are not fully decoupled for reasons described in the text. The data were acquired with a total acquisition time of 1 s in both t2 and fi using a 60Hz/i window. The selective 180° pulse was a 50 ms Q3 Gaussian cascade, and the gradient strength was 1% of the maximum 53 G cm 0 The broadband 180° pulses were BIPs (720.50.20) applied for 100 Xs at a Bi field strength of 20 kHz.

The pulse sequence resembles superficially that of the sensitivity enhanced HSQC [462]. Obviously neither proton during nor N during the acquisition f2 should be decoupled to maintain the multiplet components. It is the latter part of the pulse sequence used for the reverse transfer from to including the gradient selection that chooses the most slowly relaxing multiplet component for the detection (Fig. 14.52). 

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