Effects of chemical exchange and dipole-dipole interactions on the proton relaxation rates of surface histidyl residues in human hemoglobins

1990 ◽  
Vol 88 (1) ◽  
pp. 42-59 ◽  
Author(s):  
Marcela Madrid ◽  
Virgil Simplaceanu ◽  
Nancy T Ho ◽  
Chien Ho
Keyword(s):  
Chemical Exchange ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Dipole Interactions

scholarly journals Revisiting paramagnetic relaxation enhancements in slowly rotating systems: how long is the long range?

2020 ◽  
Author(s):  
Giovanni Bellomo ◽  
Enrico Ravera ◽  
Vito Calderone ◽  
Mauro Botta ◽  
Marco Fragai ◽  
...  
Keyword(s):  
Chemical Exchange ◽  
Protein Structure Determination ◽  
Bulk Water ◽  
Water Proton ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Rotating Systems ◽  
Complete Relaxation ◽  
Nuclear Magnetization ◽  
Order Of Magnitude

Abstract. Cross relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than one order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation matrix approach. The calculations show that the Solomon dependence of the relaxation rates on the metal-proton distance (as r−6) can be incorrect for protons farther than 15 Å from the metal, and thus can originate sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected from the Solomon equation. Therefore, it may contribute significantly to the water proton relaxation rates measured at MRI magnetic fields in the presence of slow-rotating nanoparticles containing paramagnetic ions and a large number of exchangeable surface protons.

scholarly journals Revisiting paramagnetic relaxation enhancements in slowly rotating systems: how long is the long range?

2021 ◽  
Vol 2 (1) ◽  
pp. 25-31
Author(s):  
Giovanni Bellomo ◽  
Enrico Ravera ◽  
Vito Calderone ◽  
Mauro Botta ◽  
Marco Fragai ◽  
...  
Keyword(s):  
Relaxation Rate ◽  
Chemical Exchange ◽  
Protein Structure Determination ◽  
Bulk Water ◽  
Paramagnetic Relaxation ◽  
Water Proton ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Rotating Systems ◽  
Order Of Magnitude

Abstract. Cross-relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than 1 order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation rate-matrix approach. The calculations show that the Solomon dependence of the paramagnetic relaxation rates on the metal–proton distance (as r−6) can be incorrect for protons farther than 15 Å from the metal and thus can cause sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected from the paramagnetic Solomon equation. Therefore, it may contribute significantly to the water proton relaxation rates measured at magnetic resonance imaging (MRI) magnetic fields in the presence of slow-rotating nanoparticles containing paramagnetic ions and a large number of exchangeable surface protons.

Temperature- and pH-dependence of proton relaxation rates in rat liver tissue

1995 ◽  
Vol 13 (3) ◽  
pp. 429-440 ◽  
Author(s):  
E. Moser ◽  
E. Winklmayr ◽  
P. Holzmüller ◽  
M. Krssak
Keyword(s):  
Rat Liver ◽  
Liver Tissue ◽  
Ph Dependence ◽  
Proton Relaxation ◽  
Relaxation Rates

Molecular Reorientation of Methanol in Mixtures with Carbon Tetrachloride

1992 ◽  
Vol 47 (7-8) ◽  
pp. 857-864 ◽  
Author(s):  
M. D. Zeidler ◽  
D. S. Gill ◽  
M. D. Zeidler
Keyword(s):  
Carbon Tetrachloride ◽  
Composition Dependence ◽  
Nmr Relaxation ◽  
Dipolar Interaction ◽  
Coupling Constants ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Molecular Reorientation ◽  
Quadrupole Coupling ◽  
Interaction Contribution

Abstract Proton and oxygen-17 nmr relaxation rates of CD317OH as well as deuteron nmr relaxation rates of CH3OD were measured in mixtures with carbon tetrachloride at different compositions and temperatures. By varying the 170-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time τ2OH of the OH bond was determined. Using these correlation times the composition dependence of the deuterium and oxygen-17 quadrupole coupling constants of methanol was derived. A strong variation of the coupling constants over the measured composition range is evident

Zur Protonenrelaxation von Wasser an Silikagelen

1967 ◽  
Vol 22 (11) ◽  
pp. 1751-1760 ◽  
Author(s):  
D. Michel
Keyword(s):  
Water Clusters ◽  
Relaxation Times ◽  
Dipolar Interaction ◽  
Relaxation Mechanism ◽  
Silica Gels ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Proton Proton ◽  
Adsorbed Molecules ◽  
Paramagnetic Impurities

In most cases the proton relaxation of adsorbed liquids and gases is caused by the proton-proton dipolar interaction and the coupling between protons and paramagnetic impurities (e. g. Fe3+-ions) of the adsorbent. The latter relaxation mechanism, however, has been neglected up till now although in some commercial silica gels it’s contribution can be the most important one (see Section 2.2). Consequently, motional phenomena of adsorbed molecules can only be studied by NMR techniques if the relative largeness of these two relaxation rates has been estimated, as can be done by investigating the dependence of proton relaxation-times on the H/D-ratio. Relaxation-time measurements in the temperature range from —100° to +80°C indicate that proton transfers occur between surface hydroxils and adsorbed particles. In a sample of 3/4 statistical monolayer the presence of two different types of water, clusters containing 95% of the adsorbed molecules with correlation time τc2=2.7 · 10-10 s (0°C), and more individually adsorbed particles with τc1 ⪆ 2.3 ·10-8 (0°C), has been inferred (see Section 2.1).

Applications of the intermolecular nuclear Overhauser effect. II. The operation of solute-site factors in the interaction of polar solutes with the solvent benzene

1983 ◽  
Vol 36 (11) ◽  
pp. 2227 ◽  
Author(s):  
GR Smith ◽  
B Ternai
Keyword(s):  
Nuclear Overhauser Effect ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Site Factors ◽  
Aromatic Solvent ◽  
Proton Proton ◽  
Solvent Interactions ◽  
Overhauser Effect ◽  
Polar Solutes ◽  
Nuclear Overhauser

By considering the technique involving the measurement of aromatic solvent-induced shifts, and the models which have been proposed from the results of such measurements, it is suggested that the use of the solvent-induced solute proton intermolecular relaxation rate [(1/T1)solvinter] is a better method to study local solvation of solute molecules. Proton relaxation rates obtained for simple solutes in the solvent benzene are analysed in terms of an interaction parameter I, which treats (1/T1)solvinter] in terms of a proton-proton pair distribution function. The resultant dependence between I and a calculated measure of the local polarity of the observed solute is discussed in terms of previously proposed models of solute-solvent interactions.

Molecular Reorientation in Liquid Methanol

1991 ◽  
Vol 46 (1-2) ◽  
pp. 89-94 ◽  
Author(s):  
R. Ludwig ◽  
D. S. Gill ◽  
M. D. Zeidler
Keyword(s):  
Nmr Relaxation ◽  
Quadrupole Coupling Constant ◽  
Dipolar Interaction ◽  
Proton Relaxation ◽  
Coupling Constant ◽  
Relaxation Rates ◽  
Molecular Reorientation ◽  
Quadrupole Coupling ◽  
Relaxation Measurements ◽  
Recent Computer

AbstractOxygen-17 enriched methanol CD317OH was synthesized and 1H as well as 17O nmr relaxation rates were measured in the temperature range 180-310 K. By varying the 17O-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time of the OH bond was determined. These results are compared to recent computer simulation data. Additional deuteron relaxation measurements on CH3OD yielded the quadrupole coupling constant which increases with falling temperature. The 17O quadrupole coupling constant shows a similar trend with temperature but not as pronounced.

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