Nuclear spin relaxation in liquids and gases

Kowalewski, Józef

doi:10.1039/9781849734851-00196

Cited by 2 publications

(3 citation statements)

References 315 publications

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“…In the present case, it is the fluctuation of the angle ϕ between the intramolecular vector connecting the two protons of the confined H 2 O molecule and the external magnetic field that is particularly important for 1 H NMR relaxation. This is directly related to the TCF of L 2 (ϕ) . In the extreme-narrowing regime, the relaxation rate in a two-spin system (a relatively good approximation for a confined water molecule) is linearly proportional to τ c .…”

Section: Resultsmentioning

confidence: 99%

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Water Molecules Confined in Cryptophane Nanocages: Structures and Dynamics Driven by Hydrogen Bonding and Water Chains

Hilla,

Vaara

2024

J. Phys. Chem. B

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Cryptophanes (Crs) are roughly spherical organic nanocages used as vehicles for hosting xenon atoms in 129 Xe NMR biosensor (XBS) structures. Crs also bind other guests, importantly water, which is abundant in biological systems. In other host cages, it has been found that the release of "high-energy" water from confinement constitutes an important contribution to the binding affinity of nonwater guests. Despite that, the role of water has received little attention in the XBS field. Based on molecular dynamics simulations in explicit water solvent, we here study the properties of confined water in three different CrA cages that have an identical interior but are functionalized with 0, 3, or 6 water solubility-enhancing, hydrophilic CH 2 COOH moieties. The number of the solubility groups is found to be a decisive factor for the structures and dynamics of the confined water. Formation of stable water-molecule chains is predicted within the cage with six hydrophilic groups, starting with the anchoring of one water molecule at the portal between the cage and the bulk solution. We find that the experimentally measured differences in the Xe-binding affinities of the cages can be related to the average number of hydrogen bonds per confined water molecule. The rotational dynamics of the confined water is significantly slower than that in the bulk, suggesting NMR relaxation measurements to study the intracavity water. The present findings reveal new details about the microscopic cryptophane−H 2 O host−guest chemistry, which will become important in the design of improved XBS devices.

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Section: Resultsmentioning

confidence: 99%

“…This reveals how fast the water molecules rotate both in confinement and outside of the cage at different distances from the surface. L 2 (ϕ) is directly related to the correlation time of the dipole–dipole mechanism of proton spin relaxation of the water molecules …”

Section: Methodsmentioning

confidence: 99%

Water Molecules Confined in Cryptophane Nanocages: Structures and Dynamics Driven by Hydrogen Bonding and Water Chains

Hilla,

Vaara

2024

J. Phys. Chem. B

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“…Equation represents the quadrupole relaxation rate relevant in the case of 7 Li relaxation. The comparison between 7 Li quadrupolar relaxation rate of three different lithium salts can be determined using eq . − R 1 Q = ( 2 π 2 25 ) ( 1 + η 2 3 ) ( e 2 Q q h ) [ τ 1 + ω Li 2 τ 2 + 4 τ 1 + 4 ω Li 2 τ 2 ] where e 2 Qq / h is the quadrupole coupling constant and is considered to be equivalent to 49 kHz as found for various Li-containing materials, η is the asymmetry parameter (equivalent to zero in the case of 7 Li), e is the electronic charge, Q is the the nuclear quadrupole moment, h is Planck’s constant, τ is the the quadrupolar correlation time, and ω Li is the Larmor precession frequency of the lithium nucleus. By considering extreme narrowing condition τ c 2 ω 2 ≪ 1, one can obtain R 1 Q describing the local dynamics of 7 Li.…”

Section: Resultsmentioning

confidence: 99%

A Heteronuclear NMR Study of Aqueous Lithium Salt Solutions of l-Alanine: Revealing Solute Hydrophobic Association through the NMR B′ Coefficient

Bhagat

Pal

2023

J. Phys. Chem. B

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In the present study, a set of heteronuclear NMR approaches has been adopted to investigate the solution behavior of a small hydrophobic solute L-alanine in the presence of lithium (Li) salts. The presence of salts plays a major role in determining the structure and solvation of biomolecules. It therefore evokes interest to understand the effect of Li salts on amino acids (alanine), the building block of biomolecules. The ionic solute dynamics in the present case has been probed using 1 H, 7 Li, and 13 C nuclei available in the aqueous Li salt solution of L-alanine. Nuclear longitudinal spin relaxation of alanine protons was examined at a variable concentration range of three lithium salts, i.e., LiCl, Li 2 SO 4 and LiClO 4 , to introduce the NMR B′ coefficient for each salt defining ionic solute/ solvent interaction in the solution. Analysis of the active relaxation mechanism of 7 Li spin−lattice relaxation further revealed the presence of alanine in the solvation shell of Li ion depending on the anionic counterpart.

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Nuclear spin relaxation in liquids and gases

Cited by 2 publications

References 315 publications

Water Molecules Confined in Cryptophane Nanocages: Structures and Dynamics Driven by Hydrogen Bonding and Water Chains

Water Molecules Confined in Cryptophane Nanocages: Structures and Dynamics Driven by Hydrogen Bonding and Water Chains

A Heteronuclear NMR Study of Aqueous Lithium Salt Solutions of l-Alanine: Revealing Solute Hydrophobic Association through the NMR B′ Coefficient

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