1,720,998 research outputs found
Interaction of Pt-compounds with human albumin by FTIR and CD. XAS on Pt(II) model compounds
No full textIntermediate states in ligand photodissociation of carboxymyoglobin studies by dispersive X-ray absorption.
No full textThe ligand photodissociation of sperm whale carboxymyoglobin (MbCO) at low temperature (15K-100K) under extended illumination has been studied by X-ray Absorption Near Edge Structure (XANES) spectroscopy using the dispersive technique. XANES simulations through the multiple scattering (MS) approach allow one to interpret the spectroscopic data in structural terms, and to investigate the Fe site structure configurations of the states that follow the CO photodissociation as a function of temperature. The Fe site in the photoproduct is unbound, with an overall structure similar to the deoxy-form (Mb) of the protein. The Fe site structure changes from T 50K (Mb**), revealing the existence of a slower unbound state Mb**. A model is proposed which includes the faster state (Mb*) as a planar porphyrin ring with a displacement of Fe from the heme plane of less than 0.3 A, and the slower state (Mb**) with a domed heme
Structure-function relationship in the serotransferrin: The role of the pH on the conformation change and the metal ions release
No full textWe report experimental evidence that the pH value of the micro-environment of the protein is the key for the conformational changes of transferrin, rather than the ligated or unligated state of the binding sites. The "open" and "closed" conformation of protein, suggested by X-ray crystallography in static condition, is triggered by the pH value and the effect is independent of the metal ion being transported. We propose a simple description of the structure-function relationship that allows this protein to deliver, in particular, iron or aluminum ions in the biological cycle
Conformational changes of bovine beta-trypsin and trypsinogen induced by divalent ions: An energy-dispersive X-ray diffraction and functional study
No full textThe radius of gyration (R-g) of bovine trypsinogen and beta-trypsin was measured by an energy-dispersive X-ray technique as a function of Ca2+ or SO42- concentration; these results have been supplemented with measurements of association equilibrium constants of Ca2+ to its binding site(s) on both serine proteases and some of their adducts (with an effector and/or an inhibitor). As a whole, all information reported in the present work demonstrates that: (i) the strains exerted by different ions on these proteases produce diverse structural modifications; and (ii) at least in the case of Ca2+, the changes in R-g can be ascribed to the direct interaction of the binding site(s) on the protein matrix with the cation. (c) 2006 Elsevier Inc. All rights reserved
X-ray small angle scattering of the human transferrin protein aggregates: A fractal study
No full textX-ray small angle scattering experiments, using a pin hole SAXS camera with Synchrotron radiation source, have been performed to study the conformational changes of lyophilized samples of Apo-, Mono-, and Diferric- human transferrin. We report the experimental evidence that the analysis of the scattered intensity through the fractal theory may give information on the particle size and its variation upon iron binding
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