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Magnetic Relaxation Dispersion (magnetic_relaxation + dispersion)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Water and urea interactions with the native and unfolded forms of a ,-barrel protein

PROTEIN SCIENCE, Issue 12 2003
Kristofer Modig
CD, circular dichroism; I-FABP, intestinal fatty acid-binding protein; MRD, magnetic relaxation dispersion; NOE, nuclear Overhauser effect Abstract A fundamental understanding of protein stability and the mechanism of denaturant action must ultimately rest on detailed knowledge about the structure, solvation, and energetics of the denatured state. Here, we use 17O and 2H magnetic relaxation dispersion (MRD) to study urea-induced denaturation of intestinal fatty acid-binding protein (I-FABP). MRD is among the few methods that can provide molecular-level information about protein solvation in native as well as denatured states, and it is used here to simultaneously monitor the interactions of urea and water with the unfolding protein. Whereas CD shows an apparently two-state transition, MRD reveals a more complex process involving at least two intermediates. At least one water molecule binds persistently (with residence time >10 nsec) to the protein even in 7.5 M urea, where the large internal binding cavity is disrupted and CD indicates a fully denatured protein. This may be the water molecule buried near the small hydrophobic folding core at the D,E turn in the native protein. The MRD data also provide insights about transient (residence time <1 nsec) interactions of urea and water with the native and denatured protein. In the denatured state, both water and urea rotation is much more retarded than for a fully solvated polypeptide. The MRD results support a picture of the denatured state where solvent penetrates relatively compact clusters of polypeptide segments. [source]

Protein self-association in solution: The bovine , -lactoglobulin dimer and octamer

PROTEIN SCIENCE, Issue 11 2003
Michael Gottschalk
Abstract We have used proton magnetic relaxation dispersion (MRD) to study the self-association of bovine , -lactoglobulin variant A (BLG-A) as a function of temperature at pH 4.7 (dimer,octamer equilibrium) and as a function of NaCl concentration at pH 2.5 (monomer,dimer equilibrium). The MRD method identifies coexisting oligomers from their rotational correlation times and determines their relative populations from the associated dispersion amplitudes. From MRD-derived correlation times and hydrodynamic model calculations, we confirm that BLG-A dimers associate to octamers below room temperature. The tendency for BLG-A dimers to assemble into octamers is found to be considerably weaker than in previous light scattering studies in the presence of buffer salt. At pH 2.5, the MRD data are consistent with an essentially complete transition from monomers in the absence of salt to dimers in 1 M NaCl. Because of an interfering relaxation dispersion from nanosecond water exchange, we cannot determine the oligomer populations at intermediate salt concentrations. This nanosecond dispersion may reflect intersite exchange of water molecules trapped inside the large binding cavity of BLG-A. [source]

Lanthanide(III) Complexes of DOTA,Glycoconjugates: A Potential New Class of Lectin-Mediated Medical Imaging Agents

CHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2004
João P. André Dr.
Abstract The synthesis and characterization of a new class of DOTA (1,4,7,10-tetrakis(carboxymethyl)-1,4,7,10-tetraazacyclododecane) monoamide-linked glycoconjugates (glucose, lactose and galactose) of different valencies (mono, di and tetra) and their SmIII, EuIII and GdIII complexes are reported. The 1H NMR spectrum of EuIII,DOTALac2 shows the predominance of a single structural isomer of square antiprismatic geometry of the DOTA chelating moiety and fast rotation about the amide bond connected to the targeting glycodendrimer. The in vitro relaxivity of the GdIII,glycoconjugates was studied by 1H nuclear magnetic relaxation dispersion (NMRD), yielding parameters close to those reported for other DOTA monoamides. The known recognition of sugars by lectins makes these glycoconjugates good candidates for medical imaging agents (MRI and gamma scintigraphy). [source]