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Polarized neutron scattering from dynamic polarised protons in organic radicals and in a radical doped protein

Mardi 23 juin 2015 11:00 - Duree : 1 heure
Lieu : Amphi Chadwick, ILL - 71 avenue des Martyrs - Grenoble

Orateur : H.B. STUHRMANN (Institut de Biologie Structurale Jean-Pierre Ebel, CEA/CNRS/UJF, F-38027 Grenoble cedex 1, France, and Helmholtz-Zentrum Geesthacht, D-21494 Geesthacht, Germany)

Motivated by potentially important applications in structural biology, experiments of time-resolved polarised neutron scattering from dynamic polarised proton spin targets were undertaken in order to elucidate the build-up of proton spin polarisation near paramagnetic centres. In this context, the observation that both nuclear relaxation [1] and dynamic nuclear polarisation [2] are mediated by a small number of protons which happen to be close to a paramagnetic centre was of particular interest as it might open the way towards a radical density map.

Our approach consisted of three steps :

i) test of organic radicals of different size like EHBA-CrV [3], DPPH and a biradical dissolved in a deuterated solvent. Both the isotopic and magnetic spin diffusion barrier are shown to exist.

ii) test of EHBA-CrV , which is known to support DNP most efficiently, in the absence of deuteration. We obtain the radius of a spherical magnetic spin diffusion barrier of 4.2 Å. Proton spin density images electron spin density.

The results from i) and ii) and in particular the lessons we have learnt from these experiments enter into

iii) the application to a protein which contains a radical, e.g. from EPR it is known that bovine catalase (4 subunits) treated with peroxyacetic acid gets one of its 20 tyrosins per subunit transformed into a radical state. Where is it ? The recent analysis of our earlier experiments of time-resolved polarised neutron scattering from dynamic polarised protons of bovine catalase confirms the radical state of tyrosine ( number 369 of the amino acid sequence) obtained from EPR.

[1] N. Bloembergen, Physica (Utrecht) 15, 386 (1949).

[2] A. Abragam, M. Goldman, Rep. Prog. Phys. 41, 395 (1978)

[3] B. van den Brandt, H. Glättli, I. Grillo, P. Hautle, H. Jouve, J. Kohlbrecher, J.A. Konter, E. Leymarie, S. Mango, R.P. May, A. Michels, H.B. Stuhrmann, O. Zimmer, European Phys. J. B 49, 157-165 (2006).

Contact : tellier@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Evènement répétitif : (General ILL Seminar - College 3) -
Evènement répétitif : (General ILL Seminar - College 8)
Site de l'évènement : Polygone scientifique

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