CLIP‐COSY: A Clean In‐Phase Experiment for the Rapid Acquisition of COSY‐type Correlations

Abstract

The COSY experiment is an essential homonuclear 2D NMR experiment for the assignment of resonances. Its multiplet line shape, however, is often overly complicated, potentially leads to signal intensity losses, and is responsible for long minimum overall acquisition times. Herein, we present CLIP-COSY, a COSY-type experiment yielding clean in-phase peaks. It can be recorded within a few minutes and benefits from enhanced signal intensities for most cross-peaks. In combination with non-uniform sampling, the experiment times can be further reduced, and the in-phase multiplets enable the application of modern homonuclear decoupling techniques in both dimensions. As antiphase cancelations are avoided, CLIP-COSY can also be applied to macromolecules and other samples with broadened lines.

Triplet NOAH supersequences optimised for small molecule structure characterisation

“…Some attractive options for the routine characterisation of small molecules are presented in Figure . These incorporate not only the commonly employed 2D homonuclear correlation elements such as TOCSY, NOESY, and ROESY but also the recently proposed CLIP‐COSY (clean in‐phase COSY) that provides for high‐resolution phase‐sensitive COSY presentation and the classic double‐quantum filtered COSY (DQF‐COSY).…”

Real‐time homonuclear broadband decoupled pure shift COSY

“…However, for molecules that exhibit broad multiplets, these methods suffer because of the antiphase components present in the F 1 / F 2 dimensions or involve longer refocusing periods, thereby considerably reduce the signal sensitivity and make the measurements difficult. In this regard, the subsequent advanced versions of COSY: (a) constant‐time (CT) COSY with gradient z‐filter, called in‐phase COSY (IP‐COSY) reported by Xia et al, and (b) clean in‐phase COSY (CLIP‐COSY) by Koos et al, has shown great potential. The IP‐COSY generates fairly strong in‐phase signals in both the dimensions, but the resolution in the indirect dimension is limited by the CT evolution.…”

“…The initial part of the PS‐IPZF‐COSY sequence uses the constant‐time (CT) t 1 evolution followed by adiabatic chirp‐shaped inversion pulses during the spatial encoding gradient (G4), which suppress the zero‐quantum magnetization with the aid of Keeler's z‐filter . In the case of PS‐CLIP‐COSY, the initial part of pulse scheme uses a perfect echo‐based in‐phase block flanked by adiabatic z‐filters, as described in the original CLIP‐COSY publication . The coupling time delay (Δ) has been optimized as follows.…”

SAN plot: A graphical representation of the signal, noise, and artifacts content of spectra

“…But in some cases, the true measure of the quality of a spectrum depends on the ratio between the level of the signals and the artifacts. An example is provided by the F1‐decoupled CLIP‐COSY experiment . The spectra it produces are quite powerful to analyze complex mixtures of compounds such as of carbohydrates because they eliminate scalar coupling structures in the vertical F1 dimension (see Figure ).…”