University of Oulu

Phys. Chem. Chem. Phys., 2023,25, 22719-22733,

NMR chemical shift of confined ¹²⁹Xe : coordination number, paramagnetic channels and molecular dynamics in a cryptophane-A biosensor

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Author: Hilla, Perttu1; Vaara, Juha1
Organizations: 1NMR Research Unit, P.O. Box 3000, FI-90014 University of Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.8 MB)
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Language: English
Published: Royal Society of Chemistry, 2023
Publish Date: 2023-11-03


Advances in hyperpolarisation and indirect detection have enabled the development of xenon nuclear magnetic resonance (NMR) biosensors (XBSs) for molecule-selective sensing in down to picomolar concentration. Cryptophanes (Crs) are popular cages for hosting the Xe “spy”. Understanding the microscopic host–guest chemistry has remained a challenge in the XBS field. While early NMR computations of XBSs did not consider the important effects of host dynamics and explicit solvent, here we model the motionally averaged, relativistic NMR chemical shift (CS) of free Xe, Xe in a prototypic CrA cage and Xe in a water-soluble CrA derivative, each in an explicit H₂O solvent, over system configurations generated at three different levels of molecular dynamics (MD) simulations. We confirm the “contact-type” character of the Xe CS, arising from the increased availability of paramagnetic channels, magnetic couplings between occupied and virtual orbitals through the short-ranged orbital hyperfine operator, when neighbouring atoms are in contact with Xe. Remarkably, the Xe CS in the present, highly dynamic and conformationally flexible situations is found to depend linearly on the coordination number of the Xe atom. We interpret the high- and low-CS situations in terms of the magnetic absorption spectrum and choose our preference among the used MD methods based on comparison with the experimental CS. We check the role of spin–orbit coupling by comparing with fully relativistic CS calculations. The study outlines the computational workflow required to realistically model the CS of Xe confined in dynamic cavity structures under experimental conditions, and contributes to microscopic understanding of XBSs.

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Series: PCCP. Physical chemistry chemical physics
ISSN: 1463-9076
ISSN-E: 1463-9084
ISSN-L: 1463-9076
Volume: 25
Issue: 34
Pages: 22719 - 22733
DOI: 10.1039/d3cp02695g
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
116 Chemical sciences
Funding: We acknowledge funding from the Academy of Finland (Grant 331008) and U. Oulu (Kvantum Institute).
Academy of Finland Grant Number: 331008
Detailed Information: 331008 (Academy of Finland Funding decision)
Copyright information: This journal is © the Owner Societies 2023. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.