Magnetic Resonance Linewidth Research Articles

A 81Br nuclear magnetic resonance study of bromide ion binding to proteins in aqueous solution

The 81Br nuclear magnetic resonance line width in aqueous bromide solutions is broadened upon the addition of various proteins. Comparison of metallo-enzymes with metal-free proteins gives evidence for bromide ion binding independent of metallic sites. The effect of temperature and pH on the 81Br resonance has been studied. Some measurements on 85Rb, 79Br and 35C1 resonances are included for comparison.

Diffusion and Relaxation Phenomena in Ice

The underlying mechanisms of several rate processes in ice are examined through cross comparisons of the processes with each other and with experimental observations. The assumption that the migration of orientational defects (Bjerrum faults) is the common origin of dielectric and elastic relaxation leads to a predicted ratio of dielectric-to-elastic relaxation time of 32, in close agreement with experiment. The conclusion that a separate process is responsible for diffusion is based on a comparison of diffusion and dielectric relaxation data. The faster diffusive motion controls the thermal equilibration of the proton spins as well as the magnetic resonance linewidths; an interstitial migration appears to be the mostlikely diffusion mechanism.

Wide line and pulsed NMR studies of carboxyl‐terminated polybutadiene polymers and binders

AbstractNuclear magnetic resonance relaxation and line width studies were performed on two carboxyl‐terminated polybutadiene polymers and their corresponding binders at temperatures from −170 to 25°C. It was observed that the line widths of the binders increased as the functionality of the corresponding liquid polymers increased. In addition, glass transition temperatures and activation energies obtained from line width measurements were determined. From pulse measurements the magnitude of the relaxation time T1 and the temperature at which T1 is a minimum were determined for a polymer and its corresponding binder. These empirical quantities for the carboxyl‐terminated polybutadiene polymers were lower than those of the corresponding binders because of less restraints in the internal motions of the polymer chain.

Physical studies of phospholipids. IX. Nuclear resonance studies of lipid-water systems

Proton magnetic resonance (p.m.r.) line widths and relaxation times have been measured with phospholipid molecules in a variety of environments including coarse aqueous dispersions, sonicated aqueous dispersions, and dissolved in organic solvents. Comparative measurements have also been made on other lipid systems. Broad lines (∼ 10 2 c/s) are observed when the phospholipids are present in a lamellar mesomorphic phase and in coarse aqueous dispersions. These line widths vary with the main magnetic field H o. High resolution p.m.r. spectra are obtained when phospholipids are present in (a) a cubic mesomorphic phase, (b) a sonicated aqueous dispersion, and (c) organic solvents. The p.m.r. data is interpreted to provide information about the motional characteristics of the phospholipids in these different environments.

Nuclear Magnetic Relaxation of 23Na in Different Phases in the Sodium Caprylate—Decanol—Water System

Abstract Nuclear magnetic resonance line-widths of 23Na have been determined at several compositions in two isotropic solution phases and five mesomorphous phases in the sodium caprylate-decanol-water system. The results obtained demonstrate that the rate of nuclear magnetic relaxation of 23Na+ is primarily determined by the number of water molecules per sodium ion. this indicates that in all the phases investigated, the sodium ions are predominantly coupled to water molecules. A comparison with 81Br nuclear magnetic relaxation data shows that the bonding of sodium ions is markedly different from that of bromide ions in systems containing association colloids and water. This diversity is found to be due to differences in ion-water coupling.

Proton magnetic resonance line widths of some paramagnetic octahedral nickel(II) and cobalt(II) complexes

The observed relatively narrow nmr linewidths of Mpy 4X 2 where M is either Ni or Co and X is a halogen or pseudohalogen are rationalized in terms of the factors leading to appropriate correlation times. For MNi, the marked dependence of the correlation time upon the nature of X is interpreted by mechanism involving electron-spin relaxation induced by modulation of the zero-field splitting by molecular tumbling. The situation is more complex for MCo, since electron-spin relaxation in this case is primarily determined by the energy separations amongst the components of the ground state manifold. The variation in these energy separations from compound to compound are poorly understood.

Nuclear Magnetic Resonance Study of Water Sorbed on Serum Albumin

Abstract The nuclear magnetic resonance line widths of water sorbed on solid bovine serum albumin have been determined as functions of temperature and water content of the albumin samples. The results indicate that, depending on its amount, the sorbed water may exist in three different states or arrangements. The first of these involves direct binding of water molecules to available polar groups on the protein, with water-water interactions being of relatively little significance. The addition of more water allows interactions among the water molecules and leads to the formation of a hydration shell, the structure of which is markedly different from that of liquid water and is determined by the protein substrate. At any temperature there is a water content past which the influence of the protein becomes of less importance than the interactions of water molecules among themselves, the hydration shell structure is disrupted, and the water structure approaches that of liquid water. The amount of water strongly influenced by the solid protein is apparently less than that for the protein in solution.

A nuclear magnetic resonance study of molecular motion and ‘guest’ structure in the clathrate hydrates of (i-C5H11)4NF and (n-C4H9)4NF

The proton magnetic resonance linewidth and second moments between 77°k and 286°k for i-amyl groups of molecules included as guests in the clathrate hydrate of (i-C5H11)4NF have been interpreted in terms of simple motional models of these guest moieties. The results complement the reported details of crystal structure of this clathrate. For the analogous hydrate containing guest n-butyl groups, proton magnetic resonance second moments in the same temperature range have supported the disordered guest structure reported from a previous x-ray diffraction study. In addition, hysteresis has been found in the second moment curve of this clathrate beyond 248°k, and this has been ascribed to a phase transition.

NMR results on the variation of T c in V 3Au with atomic ordering

The superconducting transition temperature, the Knightshift and the nuclear magnetic resonance line width of vanadium were measured in V 3Au compounds as a function of ordering.

Damping of magnetic domain wall motion by manganic ions in manganese ferrite

Published values of the magnetic domain wall mobility and ferromagnetic resonance linewidth for manganese rich manganese ferrite are shown to be consistent with one another on the basis of an atomic model for energy relaxation via manganic ions. The discrepancy which existed according to the previous phenomenological discussion is therebye resolved.

Chemical Rate Processes and Magnetic Resonance Linewidths

Chemical Rate Processes and Magnetic Resonance Linewidths

Experimental Test for the Suhl-Nakamura Interaction inMn1−xCoxO andMn1−xNixO

The ${\mathrm{Mn}}^{55}$ zero-field nuclear magnetic resonance (NMR) linewidth has been studied as a function of concentration in the antiferromagnetic compounds ${\mathrm{Mn}}_{1\ensuremath{-}\mathrm{x}}$${\mathrm{Co}}_{\mathrm{x}}$O and ${\mathrm{Mn}}_{1\ensuremath{-}\mathrm{x}}$${\mathrm{Ni}}_{\mathrm{x}}$O. The results suggest that if the Suhl-Nakamura interaction is the principal NMR linewidth mechanism, then its range in MnO is of the order of one lattice constant.

Nuclear magnetic resonance study of molecular motions in some crystalline polymers

AbstractNuclear magnetic resonance linewidth studies are made concerning the molecular motions in crystalline polymers moh as polyethylene, polytetrafluoroethylene, and trans‐1,4‐polybutadiene. (1) The γ (local mode) relaxation of polyethylene is studied based on the temperature variation of mobile fraction. The range of the β (primary) dispersion of linear polyethylene is shown to spread far wider than that of branched polyethylene, whereas its lower limit (Tg−) is the same for the two. (2) Concerning polytetrafluoroethylene, a third NMR component is found in addition to narrow and broad‐line components, and the third phase of molecular aggregation is assumed to be intermediate between the amorphous and crystalline phases. The notion of the intermediate phase (an array of rodlike molecules) is instrumental in clarifying the complicated viscoelastie behavior by admitting two glass transitions in the polymer. (3) At the solid‐phase transition of trans‐1,4‐polybutadiene, a huge‐scale motional narrowing of the NMR absorption line takes place, indicating the onset of rodlike rotation of the molecules belonging to the crystalline phase. Above the phase transition temperature, the polymer crystal is “plastic”.

Deuteron magnetic resonance absorption in polycrystalline heavy methane between 1.4 and 73°K

The deuteron magnetic resonance line width and second moment in polycrystalline heavy methane have been measured between 1.4 and 73°K. Below the line width transition, caused by diffusion, the observed quantities stayed essentially constant to the lowest temperature investigated. A qualitative interpretation is given.

Theory of Exchange-Narrowed Magnetic-Resonance Linewidth at Finite Temperature

General formulas are derived for the width of an exchange-narrowed magnetic-resonance absorption line at a finite temperature where the Zeeman and/or exchange energies can be comparable to the thermal energy $\mathrm{kT}$. The perturbation which gives rise to line broadening also is allowed to be comparable to $\mathrm{kT}$ in our treatment, and this marks a departure from previous theories of exchange narrowing. The relaxation-function approach of Kubo and Tomita is used, and it is assumed, as in the infinite-temperature limit, that the appropriate correlation times are sufficiently short. We show that the correlation function $〈{M}_{x}(t){M}_{x}(0)〉$ of the $x$ component of the magnetization has an apparent relaxation rate which is given by an obvious extension of the Van Vleck moments formula to finite temperature. This relation holds for an arbitrary ratio of perturbation energy to $\mathrm{kT}$. However, it appears that only if the perturbation energy is much less than $\mathrm{kT}$ can this relaxation function be simply related to ${\overline{M}}_{x}(t)$, which describes relaxation of the macroscopic magnetization. If this is the case, then an unambiguous result for the linewidth is obtained which is clearly related to Van Vleck's infinite-temperature theory.

Nuclear Magnetic Resonance Line Widths of Angular Methyl Groups in Decalins, Steroids, and N-Methylquinolizidinium Ions. Determination of Ring Fusion Stereochemistry

Nuclear Magnetic Resonance Line Widths of Angular Methyl Groups in Decalins, Steroids, and N-Methylquinolizidinium Ions. Determination of Ring Fusion Stereochemistry

Exchange interactions from nuclear magnetic resonance linewidths

The exchange interactions in RbMnF3, KMnF3 and MnF2 have been deduced from 19F nuclear magnetic resonanace linewidth measurements. The calculations were carried through not so much to obtain an accurate value for J, the exchange integral, but to test the theory of linewidth on substances in which J is well known. It is found that the theory gives a better than order-of-magnitude estimate of J, but not precise quantitative results.

Motion of Localized Triplet Excitons

A theory is developed for exciton—phonon interactions in ionic molecular crystals showing triplet-exciton magnetic resonance. By using a simple model for the phonon Hamiltonian it is shown that the triplet excitons tend to be localized, or ``self-trapped,'' and to move in a diffusional manner. The activation energy for diffusion is found to be essentially ½Λ, where Λ is the ``self-energy'' of the triplet exciton due to exciton—phonon interaction. It is suggested that the anomalous excess activation energy for exciton—exciton spin-exchange line broadening is ½Λ rather than the phonon-coupled exciton—exciton repulsion suggested previously. It is also shown that exciton creation and annihilation with the absorption and emission of phonons has no significant effect on the exciton magnetic resonance linewidths at low temperatures.

Proton Magnetic Resonance Line Widths, Ligand Exchange, and Electronic Relaxation Times for Some Arylphosphine Complexes of Cobalt(II) and Nickel(II)1a

Proton Magnetic Resonance Line Widths, Ligand Exchange, and Electronic Relaxation Times for Some Arylphosphine Complexes of Cobalt(II) and Nickel(II)^1a

Measurement of brittleness temperature of neoprene by proton magnetic resonance: Effect of plasticizers

AbstractProton magnetic resonance (PMR) line widths, δH, have been determined as a function of temperature for a number of neoprene (polychloroprene) samples. The measurements were made on raw neoprenes (type W, WRT, and GNA) and on neoprenes with plasticizers in both the unvulcanized and vulcanized states. An excellent correlation of the temperature of line narrowing with brittleness temperature found by mechanical tests is reported. The results indicate that PMR may be of value in studying plasticizer properties and in measuring glass temperatures in a manner dependent only on molecular motions rather than on the nature of a mechanical test or on sample statistics.