Messung kernmagnetischer Relaxationszeiten in Hochauflösung mittels schneller adiabatischer Passagen

1970 ◽  
Vol 25 (11) ◽  
pp. 1674-1680
Author(s):  
Hans Lütje
Keyword(s):  
High Resolution ◽  
Polyethylene Oxide ◽  
Magnetic Relaxation ◽  
Chemical Shifts ◽  
Signal To Noise Ratio ◽  
Relaxation Times ◽  
Resonance Signal ◽  
Additional Equipment ◽  
Relaxation Measurements ◽  
Fast Passage

Abstract The nuclear magnetic relaxation times T1 and T2 may be determined by observing the relaxation that follows after a stop of an adiabatic fast passage at different points of the resonance signal. High resolution measurements are possible with external proton stabilization during the relaxation process if the chemical shifts are larger than 1 ppm and the relaxation times are longer than 1 sec. If no high resolution is required the lower limit is 0.2 seconds. Relaxation measurements are possible using conventional NMR-spectrometers without additional equipment. Since the signal to noise ratio is favourable, rather dilute solutions may be investigated. Relaxation measurements on benzene, on 4 different protons of 4-dimethylamino-benzaldehyde and on polyethylene oxide in solution are reported.

Nuclear Magnetic Relaxation by Anisotropy of the Chemical Shift

1972 ◽  
Vol 27 (10) ◽  
pp. 1456-1458 ◽  
Author(s):  
J Blicharski
Keyword(s):  
Chemical Shift ◽  
Magnetic Relaxation ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Nuclear Magnetic Relaxation ◽  
Nuclear Magnetic

Abstract The relaxation times T1 , T2 , T1Q and T2Q are calculated in the weak collision case in the presence of anisotropy of the chemical shifts.

Keto-Enol Tautomerism of Dimedone Studied by Dynamic NMR

1996 ◽  
Vol 50 (11) ◽  
pp. 1408-1412 ◽  
Author(s):  
Antonio Martínez-Richa ◽  
Guillermo Mendoza-Díaz ◽  
Pedro Joseph-Nathan
Keyword(s):  
High Resolution ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Tautomeric Equilibrium ◽  
Spin Lattice Relaxation ◽  
Exponential Factor ◽  
Spin Lattice ◽  
C Nmr ◽  
Coalescence Temperature

The keto-enol tautomeric equilibrium of dimedone has been investigated by high-resolution 13C NMR spectroscopy. Kinetic information of the solution keto-enol tautomerism for dimedone in DMSO, in the temperature range of 25–85 °C, was derived from line shape measurements in a 75-MHz spectrometer. A value of 3.43 Kcal/mol was found for the Arrhenius activation energy Ea and of 1.07 × 106 s−1 for the pre-exponential factor A. With the use of the observed chemical shifts in the high-resolution 13C-NMR spectra of dimedone in the solid state, an estimate coalescence temperature of 240 K for dimedone in DMSO was obtained by extrapolation of the experimental curve. The estimated free energy of activation at the coalescence temperature, Δ Gc≠, is 10.8 Kcal/mol. Finally, the 13C spin-lattice relaxation times, T1(13C), in solid dimedone were measured as a function of temperature in the range of 25 to 90 °C. The data are discussed in terms of the different motional environments that result from the geometric restrictions imposed by hydrogen bonding in the crystal structure.

High resolution 119Sn nuclear magnetic resonance studies by pulse Fourier transform

1977 ◽  
Vol 55 (6) ◽  
pp. 927-931 ◽  
Author(s):  
C. R. Lassigne ◽  
E. J. Wells
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
High Resolution ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Spin Rotation ◽  
Tin Compounds ◽  
Magnetic Resonance Studies ◽  
Scalar Contribution

The T1's, linewidths (T2's), and chemical shifts of 119Sn nuclei in a variety of tin compounds have been surveyed using pulse Fourier transform techniques. The results span the very large chemical shift range for tin-119 (∼2000 ppm), and indicate rather short T1 values with widely varied T2 relaxation times. Possible mechanisms are discussed for both T1 and T2 relaxation times. Our results show an approximate correlation between T1 (119Sn) and the paramagnetic contribution to the observed shielding of the 119Sn nucleus, indicating that apart from a large scalar contribution in Sn(IV) iodides and bromides, the dominant 119Sn T1 mechanism is spin rotation interaction.

Notizen:Kernmagnetische Relaxationszeit-Messungen an OH-Protonen einer kristallinen Kieselsäure/ Nuclear Magnetic Relaxation Measurements on the OH-Protons of a Crystalline Silicic Acid

1975 ◽  
Vol 30 (10) ◽  
pp. 1330-1332 ◽  
Author(s):  
E. K.-H. Wittich ◽  
J. Voitländer ◽  
G. Lagaly
Keyword(s):  
Thermal Decomposition ◽  
Silicic Acid ◽  
Magnetic Relaxation ◽  
Interlayer Space ◽  
Relaxation Times ◽  
Water Molecules ◽  
Relaxation Processes ◽  
Relaxation Measurements ◽  
Silicate Layers ◽  
Crystalline Silicic Acid

Abstract The transversal relaxation times of the OH-protons of a crystalline silicic acid were measured. Two relaxation processes, clearly separated from each other, are related to the OH-protons in the silicate layers and to the OH-protons of water molecules in the interlayer spaces. From the initial magnetizations information is obtained about the water content in the interlayer space which does well agree with results given in thermal decomposition curves.

scholarly journals Fourier Transform NM R Investigations of 77Se in Aqueous Solutions

1978 ◽  
Vol 33 (9) ◽  
pp. 1025-1028 ◽  
Author(s):  
W. Koch ◽  
O. Lutz ◽  
A. Nolle
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Aqueous Solutions ◽  
Magnetic Moment ◽  
Infinite Dilution ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Recovery Method ◽  
A Value ◽  
Nmr Signals

In solutions of H2SeO3, Na2SeO3 , NaHSeO3 and Na2SeO4 in H2O NMR signals of 77Se have been observed. In these solutions chemical shifts were determined. In a 4 molal solution of Na2SeO3 the ratio of Larmor frequencies υ(77Se)/υ(1H) has been measured with a high-resolution probe. A value of the magnetic moment of 77Se in Na2SeO3 at infinite dilution in H2O is given: |μ(77Se)| = 0.533 299 6(7)μN. Relaxation times T1 have been measured by the inversion-recovery method. In a 4 molal solution of Na2SeO3 in H2O a NOE enhancement of 0.4(1) could be observed.

Progress in high-resolution CRYO-SEM imaging of viral particles

1996 ◽  
Vol 54 ◽  
pp. 818-819
Author(s):  
Ya Chen ◽  
Geoffrey Letchworth ◽  
John White
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Structural Information ◽  
Signal To Noise Ratio ◽  
Flexible Structures ◽  
Simian Virus ◽  
Topographic Features ◽  
Viral Particles ◽  
Scanning Electron

Low-temperature high-resolution scanning electron microscopy (cryo-HRSEM) has been successfully utilized to image biological macromolecular complexes at nanometer resolution. Recently, imaging of individual viral particles such as reovirus using cryo-HRSEM or simian virus (SIV) using HRSEM, HV-STEM and AFM have been reported. Although conventional electron microscopy (e.g., negative staining, replica, embedding and section), or cryo-TEM technique are widely used in studying of the architectures of viral particles, scanning electron microscopy presents two major advantages. First, secondary electron signal of SEM represents mostly surface topographic features. The topographic details of a biological assembly can be viewed directly and will not be obscured by signals from the opposite surface or from internal structures. Second, SEM may produce high contrast and signal-to-noise ratio images. As a result of this important feature, it is capable of visualizing not only individual virus particles, but also asymmetric or flexible structures. The 2-3 nm resolution obtained using high resolution cryo-SEM made it possible to provide useful surface structural information of macromolecule complexes within cells and tissues. In this study, cryo-HRSEM is utilized to visualize the distribution of glycoproteins of a herpesvirus.

The High Resolution NMR Spectra of Pesticides. II. The DDT-Type Compounds

1969 ◽  
Vol 52 (5) ◽  
pp. 1074-1092 ◽  
Author(s):  
L H Keith ◽  
A L Alford ◽  
A W Garrison
Keyword(s):  
Nuclear Magnetic Resonance ◽  
High Resolution ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Aromatic Rings ◽  
Nuclear Magnetic Resonance Spectra ◽  
High Resolution Nmr ◽  
Related Compounds ◽  
Deshielding Effect

Abstract The high resolution nuclear magnetic resonance spectra of the DDT class of pesticides and related compounds are discussed, including a study of the resonances of the aromatic protons as they are affected by various substiluents. The CCl3 moiety on the α-carbon strongly deshields the ortho protons on the aromatic rings, and this deshielding effect is greatly enhanced by substitution of a chlorine ortho rather than para on the aromatic ring. These deshielding effects are explained by a consideration of the electronegativity of the substituents and the stereochemistry of the molecule. The chemical shifts and coupling constants are tabulated.

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