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Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)Xe

Spin exchange between different chemical environments is an important observable for characterizing chemical exchange kinetics in various contexts, including protein folding, chelation chemistry, and host–guest interactions. Such spins experience effective spin–spin relaxation rate, R(2,eff), that t...

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Autores principales: Kunth, Martin, Schröder, Leif
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society of Chemistry 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8178811/
https://www.ncbi.nlm.nih.gov/pubmed/34163587
http://dx.doi.org/10.1039/d0sc04835f
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author Kunth, Martin
Schröder, Leif
author_facet Kunth, Martin
Schröder, Leif
author_sort Kunth, Martin
collection PubMed
description Spin exchange between different chemical environments is an important observable for characterizing chemical exchange kinetics in various contexts, including protein folding, chelation chemistry, and host–guest interactions. Such spins experience effective spin–spin relaxation rate, R(2,eff), that typically shows a dispersive behavior which requires detailed analysis. Here, we describe a class of highly simplified R(2,eff) behavior by relying on hyperpolarized (129)Xe as a freely exchanging ligand reporter. It provides large chemical shift separations that yield reduced expressions of both the Swift–Connick and the Carver–Richards treatment of exchange-induced relaxation. Despite observing a diamagnetic system, R(2,eff) is dominated by large Larmor frequency jumps and thus allows detection of otherwise inaccessible analyte concentrations with a single spin echo train (only 0.01% of the overall hyperpolarized spins need to be transiently bound to the molecule). The two Xe hosts cryptophane-A monoacid (CrA-ma) and cucurbit[6]uril (CB6) represent two exemplary families of container molecules (the latter one also serving as drug delivery vehicles) that act as highly efficient phase shifters for which we observed unprecedented exchange-induced relaxivity r(2) (up to 866 s(−1) mM(−1)). By including methods of spatial encoding, multiple data points can be collected simultaneously to isolate the exchange contribution and determine the effective exchange rate in partially occupied binding sites with a single delivery of hyperpolarized nuclei. The relaxivity is directly related to the guest turnover in these systems and temperature-dependent measurements yield an activation energy of E(A) = 41 kJ mol(−1) for Xe@CrA-ma from simple relaxometry analysis. The concept is transferable to many applications where Xe is known to exhibit large chemical shifts.
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spelling pubmed-81788112021-06-22 Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)Xe Kunth, Martin Schröder, Leif Chem Sci Chemistry Spin exchange between different chemical environments is an important observable for characterizing chemical exchange kinetics in various contexts, including protein folding, chelation chemistry, and host–guest interactions. Such spins experience effective spin–spin relaxation rate, R(2,eff), that typically shows a dispersive behavior which requires detailed analysis. Here, we describe a class of highly simplified R(2,eff) behavior by relying on hyperpolarized (129)Xe as a freely exchanging ligand reporter. It provides large chemical shift separations that yield reduced expressions of both the Swift–Connick and the Carver–Richards treatment of exchange-induced relaxation. Despite observing a diamagnetic system, R(2,eff) is dominated by large Larmor frequency jumps and thus allows detection of otherwise inaccessible analyte concentrations with a single spin echo train (only 0.01% of the overall hyperpolarized spins need to be transiently bound to the molecule). The two Xe hosts cryptophane-A monoacid (CrA-ma) and cucurbit[6]uril (CB6) represent two exemplary families of container molecules (the latter one also serving as drug delivery vehicles) that act as highly efficient phase shifters for which we observed unprecedented exchange-induced relaxivity r(2) (up to 866 s(−1) mM(−1)). By including methods of spatial encoding, multiple data points can be collected simultaneously to isolate the exchange contribution and determine the effective exchange rate in partially occupied binding sites with a single delivery of hyperpolarized nuclei. The relaxivity is directly related to the guest turnover in these systems and temperature-dependent measurements yield an activation energy of E(A) = 41 kJ mol(−1) for Xe@CrA-ma from simple relaxometry analysis. The concept is transferable to many applications where Xe is known to exhibit large chemical shifts. The Royal Society of Chemistry 2020-10-19 /pmc/articles/PMC8178811/ /pubmed/34163587 http://dx.doi.org/10.1039/d0sc04835f Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by-nc/3.0/
spellingShingle Chemistry
Kunth, Martin
Schröder, Leif
Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)Xe
title Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)Xe
title_full Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)Xe
title_fullStr Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)Xe
title_full_unstemmed Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)Xe
title_short Binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)Xe
title_sort binding site exchange kinetics revealed through efficient spin–spin dephasing of hyperpolarized (129)xe
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8178811/
https://www.ncbi.nlm.nih.gov/pubmed/34163587
http://dx.doi.org/10.1039/d0sc04835f
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