Electronic relaxation of a copper(II) dimer in a macromolecular complex as evaluated from solvent proton relaxation

Three independent solution spectroscopic techniques (solvent proton relaxation enhancement, circular dichroism, and high resolution 220 MHz proton magnetic resonance spectroscopy) have been utilized to demonstrate metal ion- and monosaccharide inhibitor-induced structural perturbations for the dimeric form of the plant lectin concanavalin A (Con A). The results indicate that (i) the occupation of the transition metal ion site S1 by Mn2+ or Zn2+ does not detectably perturb the demetallized protein conformation, (ii) the binding of Ca2+ to the Con A – Mn2+ or Con A – Zn2+ complexes perturbs the protein structure in the vicinity of the S1 site as well as at points remote from the S1–S2 double ion site, and (iii) the binding of the monosaccharide inhibitor α-methyl-D-mannopyranoside to the fully metallized Con A complex also significantly perturbs the structural features of the protein.A detailed radio frequency dependence analysis of the Ca2+ effect on the solvent proton relaxation enhancement properties of the Con A – Mn2+ complex indicates that the considerable reduction in the observed enhancement upon Ca2+ binding principally results from an approximate 120-fold decrease in the single Mn2+ water of hydration exchange rate. The 220 MHz proton magnetic resonance spectra for Con A indicate that this form of spectroscopy is the most useful of those utilized in detailing the solution structural features of this lectin, and a tentative assignment for the C-2-H proton of histidine residue 24 (the S1 site ligand) has been proposed.

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Temperature and frequency dependence of solvent proton relaxation rates in solutions of manganese(II) carbonic anhydrase

Biochemistry ◽

10.1021/bi00673a008 ◽

1975 ◽

Vol 14 (2) ◽

pp. 242-248 ◽

Cited By ~ 57

Author(s):

Amos Lanir ◽

Sonia Gradstajn ◽

Gil Navon

Keyword(s):

Carbonic Anhydrase ◽

Frequency Dependence ◽

Proton Relaxation ◽

Relaxation Rates ◽

Solvent Proton

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Molecular Motion in Liquids and Solutions. II.

Zeitschrift für Naturforschung A ◽

10.1515/zna-1966-0805 ◽

1966 ◽

Vol 21 (8) ◽

pp. 1224-1230 ◽

Cited By ~ 14

Author(s):

G. J. Krüger ◽

W. Müller-Warmuth ◽

R. Van Steenwinkel

Keyword(s):

Molecular Motion ◽

Dipole Interaction ◽

Proton Relaxation ◽

Frequency Range ◽

Kcal Mole ◽

Relative Contribution ◽

Random Motions ◽

Large Frequency ◽

Solvent Proton

Two methods are utilized to study the relaxation behaviour and molecular motion in solutions of free radicals in toluene: the investigation of longitudinal and transversal solvent proton relaxation at a properly chosen frequency (48 MHz), and the determination of enhancement factors of the dynamic proton polarization over a large frequency range. The temperature dependence of the quantities concerned is measured between +70°C and —120°C.The results can be interpreted in terms of a pure dipole-dipole interaction between proton and electron spins whose time dependence is provided by translational random motions of the molecules and rotational tumbling of associated complexes. The activation energies for both processes are 3.1 kcal/mole and 7.8 kcal/mole, respectively. The solvation is only very weak. The relative contribution of rotational tumbling is R=0.26, from which the average co-ordination number is estimated to be less than one.

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Nitroxide radical induced solvent proton relaxation: Measurement of localized translational diffusion

The Journal of Chemical Physics ◽

10.1063/1.448147 ◽

1984 ◽

Vol 81 (9) ◽

pp. 4038-4045 ◽

Cited By ~ 128

Author(s):

C. F. Polnaszek ◽

R. G. Bryant

Keyword(s):

Nitroxide Radical ◽

Translational Diffusion ◽

Proton Relaxation ◽

Relaxation Measurement ◽

Solvent Proton

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