journal article
LitStream Collection
Home
doi: 10.1002/mrc.5378pmid: 37449419
The present review is focused on the most recent achievements in the application of liquid phase 17O nuclear magnetic resonance (NMR) to inorganic, organic, and biochemical molecules focusing on their structure, conformations, and (bio)chemical behavior. The review is composed of four basic parts, namely, (1) simple molecules; (2) water and hydrogen bonding; (3) metal oxides, clusters, and complexes; and (4) biological molecules. Experimental 17O NMR chemical shifts are thoroughly tabulated. They span a range of as much as almost 650 ppm (from −35.6 to +610.0 ppm) for inorganic and organic molecules, whereas this range is much wider for biological species being of about 1350 ppm (from −12 to +1332 ppm), and in the case of hemoproteins and heme‐model compounds, isotropic chemical shifts of up to 2500 ppm were observed. The general prospects and caveats in the modern development of the liquid phase 17O NMR in chemistry and biochemistry are critically discussed and briefly outlined in view of their future applications.
Silva Elipe, Maria Victoria; Ndukwe, Ikenna Edward; Navarro‐Vázquez, Armando
doi: 10.1002/mrc.5380pmid: 37530063
High‐temperature superconducting (HTS) materials have recently been incorporated into the construction of HTS cryogen‐free magnets for nuclear magnetic resonance (NMR) spectroscopy. These HTS NMR spectrometers do not require liquid cryogens, thereby providing significant cost savings and facilitating easy integration into chemistry laboratories. However, the optimal performance of these HTS magnets against standard cryogen NMR magnets must be evaluated, especially with demanding modern NMR applications such as NMR in anisotropic media. The stability of the HTS magnets over time and their performance with complex pulse sequence experiments are the main unknown factors of this new technology. In this study, we evaluate the utility of our prototype 400 MHz cryogen‐free power‐driven HTS NMR spectrometer, installed in the fumehood of a chemistry laboratory, for stereochemical analysis of three commercial natural products (artemisinin, artemether, and dihydroartemisinin) via measurement of anisotropic NMR data, in particular, residual dipolar couplings. The accuracy of measurement of the anisotropic NMR data with the HTS magnet spectrometer is evaluated through the CASE‐3D fitting protocol, as implemented in the Mestrenova‐StereoFitter software program.
Vasquez, Joseph K.; Zhou, Zhe; Clark, Brian; Kimenai, Ad J.; Reiner, Benjamin R.; Rau, Nathan J.; Baugh, Dan; Eldred, Donald V.; Paradkar, Manjiri; Zheng, Chen; DeFelippis, Jim; Potter, Janece M.; Qiu, Xiao Hua; Zong, Xiaohong; Young, Wenshiue Owen; Fitzgibbons, Thomas;
Showing 1 to 6 of 6 Articles
doi: 10.1002/mrc.5384pmid: 37551084
13C nuclear magnetic resonance (NMR) is traditionally considered an insensitive technique, requiring long acquisition times to measure dilute functionalities on large polymers. With the introduction of cryoprobes and better electronics, sensitivity has improved in a way that allows measurements to take less than 1/20th the time that they previously did. Unfortunately, a high Q‐factor with cryoprobes creates baseline curvature related to acoustic ringing that affects quantitative NMR analyses. Manual baseline correction is commonly used to compensate for the baseline roll, but it is a time‐intensive process. The outcome of manual baseline correction can vary depending on processing parameters, especially for complicated spectra. Additionally, it can be challenging to distinguish between broad peaks and baseline rolls. A new anti‐ring pulse sequence (zgig_pisp) was previously reported to improve on the incumbent single pulse experiment (zgig). The original report presented limited comparison data with 13C NMR, but a thorough validation is needed before broader implementation can be considered. In this work, we report the round‐robin testing and comparison of zgig_pisp and zgig pulse sequences. During the testing phase, we found that zgig_pisp is practically equivalent to zgig to ±2% for the majority of integrals examined. Additionally, a short broadband inversion pulse (BIP) was demonstrated as an alternative to the originally reported adiabatic CHIRP shaped pulse. The zgig_pisp pulse sequence code for Bruker spectrometers is also simplified.