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| Heinrich Stuhrmann - | |
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H.B. Stuhrmann
GKSS Forschungszentrum Geesthacht, and
Institut de Biologie Structurale Jean-Pierre Ebel, CEA/CNRS/UJF
41 rue Jules Horowitz, F-38027 Grenoble
It was in summer 1979 when PIA after an unexpectedly short commissioning
time started to accumulate positrons for the injection into PETRA.
DORIS thus became available for experiments of synchrotron radiation.
As this happened during the metamorphosis of F41 into HASYLAB, the
EMBL Outstation turned out to be the only possible client. The
directors of DESY decided to run DORIS for the EMBL Outstation as the
first and only main user during the summer holidays 1979.
The unprecedented high quality of synchrotron radiation emitted by
the positrons of DORIS and especially the stable beam position opened
new possibilities in synchrotron radiation research. The friends of the
EMBL Oustation from all over Europe cancelled their holidays to profit
from this unique occasion. The experimental results, in particular those
of time-resolved X-ray diffraction and small-angle scattering were ground
breaking.
For the first time data from anomalous scattering of a solution of
ferritin were accurate enough to follow the apparent contrast at
wavelengths near the K-edge of iron (lambda=1.73Å [1]. This finding
initiated a series of experiments on metal proteins (hemoglobin, catalase,
ATCase), membranes, polyelectrolytes (counterion distribution of tRNA and
ribosomes), polymers (e.g. iodine in polyacetylene at the LIII edge,
lambda=2.7Å, and various metal alloys.
While the wavelength range accessible at the EMBL anomalous
small-angle scattering beamline was limited to lambda < 3 Å (recently
defined as 'softer' X-rays [2]), wavelengths up to 7 Å could be
reached at the beamline A1 of HASYLAB. Thus lighter elements like
phosphorus, sulphur, and chlorine became resonant labels in anomalous
X-ray diffraction both in life sciences and materials research.
Anomalous small-angle scattering from phosphorus in ribosomes at
wavelengths near the K-edge of phosphorus (lambda=5.76 Å is an
example [3]. The most extreme demands were encountered in protein
crystallography using the method of multi-wavelength anomalous
diffraction at wavelengths beyond 5 Å [4]. Multiwire proportional
counters from the EMBL Outstation at Grenoble were a good choice.
This is also true for image plates which are being used at the
beamline ID01 of ESRF, Grenoble. With a crystal of tetragonal
lysozyme, the diffracted intensity drops by about one order of magnitude
only, on passing from lambda = 2.7 Å to lambda = 5.7 Å [5].
The strong anomalous dispersion near the MV edge of uranium has been
used to re-determine the structure of lysozyme [6]. More recent
experiments focus on anomalous diffraction near the K-edge of
phosphorus, aiming at the study of membrane proteins [7].
In spite of the more or less continuous effort to advance soft
X-ray diffraction in protein crystallography it must be admitted that
this technique is still in its infancy [2]. The collection of a
reasonably complete data is relatively long mainly because of lacking
automation. Radiation damage is not too excessive, provided the
detector system is efficient. Small crystals have a real chance.
The situation is quite different for the study of less vulnerable
substances, where the use soft X-ray diffraction has become an easy
routine. The measurement of DAFS (diffraction anomalous fine structure)
from a chlorobismuthate crystal taken at 78 wavelengths near the K-edge
of chlorine (lambda = 4.4 Å and near the MV edge of bismuth
(lambda = 4.76 Å) is an example [8].
[1] H.B. Stuhrmann, Acta Cryst. (1980) A36, 996-1001
[2] K. Djinovic Carugo, J. R. Helliwell, H. Stuhrmann & M.S. Weiss (2004) J. Synchrotron Radiation (submitted)
[3] M. Hütsch(1993), Thesis, University of Hamburg
[4] S. Stuhrmann, K.S. Bartels, W. Braunwarth, R. Doose, F. Dauvergne, A. Gabriel, A. Knöchel, M. Marmotti, H.B. Stuhrmann, C. Trame, & M.S. Lehmann (1997). J. Synchrotron Rad. 4, 298-310.
[5] P. Carpentier, P. Boesecke, P., J.-M. Bois, M.-L. Chesne, E. Fanchon, R. Kahn, H. Stuhrmann, & J. Vicat. (2002). Acta Physica Polonica, 101, 603-612.
[6] M.-L. Chesne (2002), Thesis, Université Joseph Fourier, Grenoble
[7] V. Biou, P. Boesecke, J.-M. Bois, G. Brandolin, R. Kahn, C. Mas, L. Nauton, H. Nury, E. Pebay-Peyroula, J. Vicat, H. Stuhrmann (2004), manuscript in preparation
[8] P. Carpentier et al. (to be published)
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