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.

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.

scholarly journals Comparison of Structure and Local Dynamics of Two Peptide Dendrimers with the Same Backbone but with Different Side Groups in Their Spacers

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1657 ◽  
Author(s):  
Sofia Mikhtaniuk ◽  
Valeriy Bezrodnyi ◽  
Oleg Shavykin ◽  
Igor Neelov ◽  
Nadezhda Sheveleva ◽  
...  
Keyword(s):  
Ion Pairs ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Peptide Dendrimers ◽  
Wide Range ◽  
Dynamics Method ◽  
Perform Computer Simulation ◽  
Good Agreement

In this paper, we perform computer simulation of two lysine-based dendrimers with Lys-2Lys and Lys-2Gly repeating units. These dendrimers were recently studied experimentally by NMR (Sci. Reports, 2018, 8, 8916) and tested as carriers for gene delivery (Bioorg. Chem., 2020, 95, 103504). Simulation was performed by molecular dynamics method in a wide range of temperatures. We have shown that the Lys-2Lys dendrimer has a larger size but smaller fluctuations as well as lower internal density in comparison with the Lys-2Gly dendrimer. The Lys-2Lys dendrimer has larger charge but counterions form more ion pairs with its NH 3 + groups and reduce the bare charge and zeta potential of the first dendrimer more strongly. It was demonstrated that these differences between dendrimers are due to the lower flexibility and the larger charge (+2) of each 2Lys spacers in comparison with 2Gly ones. The terminal CH2 groups in both dendrimers move faster than the inner CH2 groups. The calculated temperature dependencies of the spin-lattice relaxation times of these groups for both dendrimers are in a good agreement with the experimental results obtained by NMR.

scholarly journals 81Br and 27Al NQR of AlBr3 · 2C5H5N, AlBr3 · 1.5CH3CN, and AlBr3 · 2CH3CN

1986 ◽  
Vol 41 (1-2) ◽  
pp. 230-235 ◽  
Author(s):  
Koji Yamada ◽  
Tsutomu Okuda ◽  
Hisao Negita
Keyword(s):  
Ion Pairs ◽  
Relaxation Times ◽  
Structural Models ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Reorientational Motion ◽  
Metal Ligands ◽  
Spin Lattice ◽  
Solid Compounds ◽  
Nqr Parameters

81Br NQR was studied in AlBr3 · 2C5H5N, AlBr3 · 1.5CH3CN, and AlBr3 · 2CH3CN. From the NQR spectra it is apparent that the solid compounds are build up by ion pairs [AlBr2(C5H5N )4+, AlBr4-], [Al(CH3CN)63+, 3AlBr4-], and [AlBr(CH3CN)52+, 2AlBr4-- CH3CN], respectively. 27Al NQR detected by SEDOR technique supports these structural models. Using these NQR parameters, the metal-ligands interactions in the six-coordinated complexes is discussed on the basis of the donor strength. In the case of AlBr3 ·2CH3CN two types of reorientational motion of the AlBr4- tetrahedra were detected from the spin lattice relaxation times and from fade-out phenomena of the 81Br NQR signals.

N.M.R. studies on myelin basic protein. IV. 13C N.M.R. of the peptide encephalitogenic in the guinea pig

1980 ◽  
Vol 33 (11) ◽  
pp. 2411 ◽  
Author(s):  
SA Margetson ◽  
WJ Moore
Keyword(s):  
Aqueous Solution ◽  
Guinea Pig ◽  
Basic Protein ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Side Chain ◽  
Aromatic Rings ◽  
Ph Titration ◽  
Spin Lattice

The encephalitogenic nonapeptide Phe1-Ser2-Trp3-Gly4-Ala5-Glu6-Gly7-Gln8- Lys9 and its [D-Ala5] analogue have been studied in aqueous solution by 13C n.m.r. spectroscopy. The resonances of all the carbons have been assigned and their pH profiles measured. The expected conformational differences are indicated by only subtle differences in long-range pH titration shifts. The spin-lattice relaxation times T1 of all the protonated carbons of the [L-Ala5] nonapeptide have been measured at 25°C. Analysis of these data in terms of effective correlation times for side-chain mobilities suggests restricted motions for the side chains of Glu6 and Gln8 and the aromatic rings of Phe1 and Trp3.

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.

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).)

A Carbon-13 Spin-Lattice Relaxation Studies of Simple Alkylsulfates and Alkylsulfonates in Aqueous Solution

1983 ◽  
Vol 38 (10) ◽  
pp. 1149-1151
Author(s):  
Kazuhiro Matsushita ◽  
Yukimasa Terada ◽  
Tadayoshi Yoshida ◽  
Hirofumi Okabayashi
Keyword(s):  
Aqueous Solution ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Polar Group ◽  
Progressive Decrease ◽  
Methyl Group ◽  
Critical Micelle Concentrations ◽  
Spin Lattice ◽  
Relaxation Studies

Abstract The C-13 spin-lattice relaxation times (T1) of a series of short-chain n-alkylsulfates and sulfonates in D2O solutions were measured at various concentrations. Even for ethylsulfate and n-propylsulfonate ions, inflections, due to association, in the reciprocal of the T1 vs. the inverse concentration plots were observed. The critical micelle concentrations (CMC's) of ethyl and butylsulfates are 3.0 and 2.5 mol/l, respectively, and those of propyl and butylsulfonate 2.3 and 1.9 mol/l, respectively. For the simple alkylsulfates, below the CMC a progressive decrease in T1 from the terminal methyl group towards the polar group was observed.

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.

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