scholarly journals Permeation of small molecules into the cavity of ferritin as revealed by proton nuclear magnetic resonance relaxation

1995 ◽  
Vol 307 (1) ◽  
pp. 253-256 ◽  
Author(s):  
D Yang ◽  
K Nagayama
Keyword(s):  
Relaxation Times ◽  
Nmr Relaxation ◽  
Maximum Size ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Proton Nuclear Magnetic Resonance ◽  
Ferric Ions ◽  
Spin Lattice ◽  
Resonance Relaxation ◽  
Pass Through

The NMR relaxation technique was used to investigate the permeation of molecules into the cavity of ferritin. Spin-lattice relaxation times in the rotating frame of various probe molecules were measured for solutions of recombinant horse L-apoferritin without iron and horse spleen apoferritin with very small amounts of ferric ions. The results show that molecules larger than the size of the ferritin channels can pass through the channels into the ferritin interior, and that the maximum size of molecules for the permeation is smaller than maltotriose.

scholarly journals Methyl Group Rotation and Tunnellingin Crystals of 5-Membered Ring Molecules

1988 ◽  
Vol 43 (1) ◽  
pp. 35-42 ◽  
Author(s):  
A.-S. Montjoie ◽  
W. Müller-Warmuth ◽  
Hildegard Stiller ◽  
J. Stanislawski
Keyword(s):  
Elevated Temperatures ◽  
Inelastic Neutron Scattering ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Inelastic Neutron ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Quantum Tunnelling ◽  
Spin Lattice

Abstract1H NMR spin-lattice relaxation times T1 and -if accessible -level-crossing peaks and inelastic neutron scattering spectra have been measured for solid 2-and 3-methylfuran, 2-and 3-methylthiophene, 3-and 4-methylpyrazole, 1-methylimidazole, and 5-methylisoxazole. From the tunnel splittings, the torsional excitations and the NMR relaxation rates, the molecular dynamics of the methyl rotators has been evaluated between the limits of quantum tunnelling at low temperatures and thermally activated random reorientation at elevated temperatures.

A proton magnetic resonance relaxation study of molecular motions in trimethylamine-borane

1976 ◽  
Vol 54 (7) ◽  
pp. 1087-1091 ◽  
Author(s):  
T. T. Ang ◽  
B. A. Dunell
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Solid Phase ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Free Induction ◽  
Resonance Spin ◽  
Resonance Relaxation

Proton magnetic resonance spin–lattice relaxation times T1 have been measured for trimethylamine-borane from 120 to 380 K, a few degrees above the melting point. Minima in T1 at 157 and 259 K are attributed to threefold reorientation of each of the three methyl groups and the borane group and to threefold reorientation of the whole molecule about the B—N axis, respectively. Activation energies for these processes were found to be 3.3 and 6.7 kcal/mol. Abrupt changes in T1 at 350 and 360 K correspond exactly with heat capacity transitions observed by other workers. The time constant for the decay of the free induction signal (FID curve) changes by two orders of magnitude at 360 K. Having a value of some 3 ms above 360 K, it shows that there must be rapid diffusion as well as molecular tumbling in the highest temperature solid phase.

14N Nuclear Magnetic Resonance Relaxation of the Nitrate Ion and Ion Pairing in Aqueous Solution

1995 ◽  
Vol 48 (2) ◽  
pp. 207 ◽  
Author(s):  
G Owens ◽  
P Guarilloff ◽  
BJ Steel ◽  
T Kurucsev
Keyword(s):  
Aqueous Solution ◽  
Ion Pairs ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Metal Nitrate ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Fast Exchange ◽  
Resonance Relaxation ◽  
Two State Model

14 N n.m.r. spin-lattice relaxation times of four metal nitrate salts were measured as a function of concentration in aqueous solution. The concentration dependence of T1 was attributed to the formation of ion pairs with increasing concentration in these solutions. The T1 data, allowing for viscosity corrections, were treated by a two-state model of 'free' and 'bound' nitrate ions and to both possibilities of slow and fast exchange between the two states. In the equilibrium expressions estimates of the relevant activity coefficients were included. The slow nitrate exchange mechanism was favoured and the values obtained for this particular mechanism compared well with those derived from alternative measurements.

scholarly journals Possibilities of proton magnetic resonance in determination the cellulose crystallinity

2019 ◽  
Vol 59 (8) ◽  
pp. 116-123
Author(s):  
Yury B. Grunin ◽  
◽  
Maria S. Ivanova ◽  
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Active Surface ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Cellulose Crystallinity ◽  
Spin Lattice ◽  
Free Induction

A layered model of the structural organization of macrofibrils of native cellulose, consisting of microfibrils, which include elementary fibrils, has been developed. A feature of the proposed model is the presence of slit-like pores between the crystalline elements of cellulose. It was found that, on average, each water molecule interacts with one glucose residue of the surface chains of cellulose with the formation of hydrogen bonds in the framework of monolayer adsorption. This allows to establish a correlation between the cellulose crystallinity and the capacity of the adsorption water monolayer on its active surface. Based on the condition of rapid molecular exchange between the adsorption water layers in the framework of the Bloembergen-Purcell-Pound theory, an approach is proposed for determination the capacity of water monolayer. The obtained values are consistent with the results of solving the Brunauer-Emmett-Teller equation for the adsorption isotherm of water on the active surface of cellulose. The Fourier transform of the free induction decay signal of cellulose allows to estimate its crystallinity at various moisture contents. Methods have been developed for assessing the crystallinity of different types of dry cellulose based on NMR relaxation parameters — spin-lattice relaxation time and spin-spin relaxation time. Using the method of deuteration of cellulose, the relaxation times of its crystalline regions were determined. The results of preliminary studies showed that the crystallinity of cotton cellulose is higher in comparison with the same parameter of woody types of cellulose. A comparison of the literature and the data we obtained using 1H-NMR relaxation confirmed the possibility of utilizing the developed methods to solve the tasks of scientific research and conducting quality control of cellulosic materials at specialized enterprises.

Ionic Dynamics in Plastic Crystal KNO2 Studied by 39K and 15N NMR

1994 ◽  
Vol 49 (1-2) ◽  
pp. 247-252 ◽  
Author(s):  
Motoko Kenmotsu ◽  
Hisashi Honda ◽  
Hiroshi Ohki ◽  
Ryuichi Ikeda ◽  
Tomoki Erata ◽  
...  
Keyword(s):  
Intermediate Phase ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
15N Nmr ◽  
Temperature Phase ◽  
Self Diffusion ◽  
Spin Lattice

AbstractThe spin-lattice relaxation time of 39K NMR observed in the low-temperature phase (T<264.1 K) of KNO2 is explained by the quadrupole mechanism contributed from a newly found NO2- motion. The in-plane C3 reorientation and the overvall NO2 rotation as well as the self-diffusion were shown in the intermediate phase (T ≤ 314.7 K) and the high-temperature plastic phase (T < melting point: 710 K), respectively, by observing 39K and 15N NMR relaxation times and 15N lineshapes.

A carbon-13 nuclear magnetic resonance relaxation study of the reentrant 60CB–80CB

1991 ◽  
Vol 69 (12) ◽  
pp. 1454-1458 ◽  
Author(s):  
J. S. Lewis ◽  
E. Tomchuk ◽  
E. Bock
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Smectic A ◽  
Relaxation Study ◽  
Pairing Model ◽  
Nematic Phases ◽  
Resonance Relaxation ◽  
Experimental Values

The carbon-13 spin-lattice relaxation times of the protonated ring carbons of octyloxycyanobiphenyl (80CB) in a 26 wt.% mixture of perdeuterated hexyloxycyanobiphenyl (60CB–d21) in 80CB are measured as a function of temperature at 22.63 MHz in the nematic (N), smectic A(SA), and reentrant nematic (RN) phases. The deuterium spectral densities of the ring deuterons of 60CB–d21 in the same sample were studied previously, and the diffusion coefficients [Formula: see text] and [Formula: see text] found in that study are used to calculate the theoretical carbon-13 relaxation times of the protonated ring carbons of 60CB. The general agreement of the theoretical values for 60CB with the experimental values for 80CB demonstrates that the two constituent molecules of the reentrant have similar motions. Small differences, similar in nature to those encountered in other studies of this interesting reentrant, however, do exist in the nematic and reentrant nematic phases and are discussed in terms of the molecular pairing model proposed by Cladis. (Phys. Rev. Lett. 35, 48 (1975).)

Boron-11, boron-10, and nitrogen-14 NMR relaxation rates and quadrupole coupling constants in BH3NH3

1992 ◽  
Vol 70 (9) ◽  
pp. 2420-2423 ◽  
Author(s):  
Glenn H. Penner ◽  
Stephen I. Daleman ◽  
Angela R. Custodio
Keyword(s):  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Coupling Constants ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Orbital Theory ◽  
Spin Lattice ◽  
Quadrupolar Coupling ◽  
Field Gradients

The 11B, 10B, and 14N spin–lattice relaxation times (T1) for aqueous solutions of BH3NH3 were measured by NMR spectroscopy. The results of this investigation are consistent with the nuclear quadrupolar coupling constants reported in previous nuclear quadrupolar resonance and microwave studies. The activation energy associated with rotational reorientation of BH3NH3 in aqueous solution is 11.7 ± 0.6 kJ/mol. Electric field gradients were calculated at various levels of abinitio molecular orbital theory, in order to obtain theoretical 14N and 11B quadrupolar coupling constants. At the highest level of calculation (CI(SD)/6-31G**//MP2/6-31G**), these are in agreement with recently reported microwave results but not with previously reported NQR experiments.

Molecular Mobility of the Water Molecules in Aqueous Sucrose Solutions, Studied by 2H-NMR Relaxation

1994 ◽  
Vol 49 (3-4) ◽  
pp. 250-257 ◽  
Author(s):  
D. Girlich ◽  
H.-D. Lüdemann
Keyword(s):  
Temperature Dependence ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Spin Lattice ◽  
Sucrose Solutions ◽  
Deuteron Spin ◽  
High Concentrations

Deuteron spin lattice relaxation times T1 of sucrose/D2O solutions are given as function of temperature, pressure, frequency and concentration. From the temperature dependence of the 2H -T1 the rotational dynamics of the hydrated sucrose complex and the water molecules are determined. For high pressure and high concentrations the temperature dependence of the water molecules is described by a Vogel-Tammann-Fulcher equation. The ideal glass transition temperatures TOH2O derived for the water molecules are at higher concentrations almost constant and smaller than the TOsuc of the sugar molecules

Nuclear magnetic resonance relaxation and anisotropic reorientation in liquid dimethylmercury

1977 ◽  
Vol 55 (8) ◽  
pp. 1303-1313 ◽  
Author(s):  
Claude R. Lassigne ◽  
E. J. Wells
Keyword(s):  
Molecular Diffusion ◽  
Symmetry Axis ◽  
Chemical Shift Anisotropy ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Rotation ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
Resonance Relaxation

Spin–lattice relaxation times of 1H, D, and 199Hg have been measured between 234 and 333 K in liquid dimethylmercury and its isotopic modifications. These measurements have allowed the relaxation mechanisms to be separated. It was found that the spin–rotation interaction is the dominating mechanism for the 199Hg relaxation at 14.1 kG even at low temperatures. We have estimated the spin–rotation constants, [Formula: see text] along with the chemical shift anisotropy [Formula: see text]It is concluded that reorientation about the symmetry axis is not well described by molecular diffusion. Reorientation of the methyl group about its symmetry axis is found to be approximately forty times faster than the reorientation about the perpendicular axis.

Molecular Mobility of Sucrose in Aqueous Solution Studied by 13C NMR Relaxation

1993 ◽  
Vol 48 (5-6) ◽  
pp. 407-413 ◽  
Author(s):  
D. Girlich ◽  
H.-D Lüdemann
Keyword(s):  
Aqueous Solution ◽  
Concentration Dependence ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Rotational Dynamics ◽  
Spin Lattice Relaxation ◽  
Rotational Mobility ◽  
Spin Lattice ◽  
The Ideal

Abstract From the temperature and concentration dependence of the 13C spin lattice relaxation times of the 12 carbon atoms of the sucrose molecule the rotational dynamics of the sugar molecules are determined. No indication for conformational mobility of the rings is found. The exocyclic hydroxymethyl groups possess extra mobility. The models used for the description are critically discussed. The temperature dependence of the rotational mobility is described by a VTF equation. The concentration dependence of the ideal glass transition temperature To for this mobility is derived.

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