Friday 12 July 2013, Sidlaw Room, 14:00-15:30
Biological dynamics and kinetics
(invited) Probing the internal dynamics of proteins
M Sharp
ESS, Sweden
To understand the function of biomolecules one must know not only their structure, but also their dynamics. One
technique that is ideally suited for this is neutron spin-echo spectroscopy (NSE), the technique with the highest
energy resolution. In this talk I will show how NSE can be used to probe the dynamics of biologically relevant
systems. One example is our study of the internal dynamics of the mercuric ion reductase, MerA, an enzyme
responsible for catalyzing the NADPH-dependent reduction of Hg(II) to uncharged, and much less harmful, Hg(0).
This enzyme consists of a large homodimeric catalytic core unit (core-MerA) which is connected to two small
metallochaperone-like N-terminal domains (NmerA) by flexible linkers. Studies of the separately expressed coreMerA and NmerA domains have shown that NmerA can bind Hg(II) with its pair of cysteines and deliver it to coreMerA for reduction. For this reason it is important to understand the internal dynamics of the intact full length
protein, in particular the motions of the NmerA domains relative to the core of the enzyme. This has proven possible
through the combination of NSE, SANS and computational simulations, and I will present our findings here.
Solvent effect on protein fast dynamics: Implications for biopreservation
V Garcia Sakai1, S Khodadadi2, M T Cicerone3, J E Curtis3, A P Sokolov4 and J H Roh5
1
ISIS Facility, UK, 2 Delft University of Technology, Netherlands, 3NIST, USA, 4Oak Ridge National
Laboratory/University of Tennessee, USA, 5US Naval Research Laboratory, USA
Protein dynamics play a significant role in the protein function, activity and stability. Stability of biological
macromolecules in different solvents is a complex function of the solvent properties and the mechanisms of
degradation. We studied dynamics of model protein, lysozyme, in three different solvents, water, glycerol and
trehalose, in the temperature range 150 K- 370 K, using dielectric spectroscopy and neutron scattering techniques.
We identified and followed different dynamical processes of lysozyme, and its solvent at ps-ns time scale. The
results demonstrate that glycerol is the most efficient in suppression of protein dynamics at lower temperature,
while trehalose works the best at high temperature.
Structure and dynamics of energy converting biological membranes
G Nagy1, L Kovács2, R Ünnep2, O Zsiros2, L Rosta2, J Pieper3, J Minagawa4, G Finazzi5, A Dér2, J Peters6, D Posselt7
and G Garab2
1
Paul Scherrer Institute, Switzerland / Hungarian Academy of Sciences, Hungary, 2Hungarian Academy of Sciences,
Hungary, 3University of Tartu, Estonia, 4 National Institute for Basic Biology (NIBB), Japan,5Centre National de la
Recherche Scientifique/Université Joseph Fourier (UJF) Commissariat à l'Energie Atomique et aux Energies
Alternatives (CEA)/Institut National Recherche Agronomique (INRA)/ Institut de Recherche en Sciences et
Technologie du Vivant (IRTSV), France, 6Institut Laue-Langevin, France / Université Joseph Fourier France; Institut de
Biologie Structurale/Jean Pierre Ebel, France, 7Roskilde University, Denmark
The understanding of the structure and dynamics of biological membranes capable of converting light energy to
chemical energy is important both in basic research and in solar energy technology.
ICNS 2013 International Conference on Neutron Scattering
Recently we have investigated energy converting biological membranes with SANS and EINS. With SANS, we
determined characteristic repeat distances and revealed light induced structural reorganizations during
photosynthesis in isolated plant thylakoid membranes and in living unicellular organisms [1-3] and intact leaves
[4] with a time resolution of seconds and minutes [5]. We also provided experimental evidence for changes in
thylakoid membrane stacking in green algae during state transitions of the photosynthetic machinery [6].
EINS measurements on Photosystem II membrane fragments, revealed a transition due to the detachment of the
oxygen evolving complex [7], and on bacteriorhodopsin containing purple membranes shed light on the effect of
Hofmeister salts on protein conformational fluctuations [8].
These studies, apart from answering questions in the field of structure and dynamics of energy converting biological
membranes demonstrate the power of neutron scattering for the study of complex biological systems.
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
Nagy G et al. 2011 Biochem J 436:225
Nagy G et al. 2012 Photosynth Res 111:71
Posselt D et al. 2012 Biochim Biophys Acta Bioenerg 1817:1220
Ünnep R et al. in preparation
Nagy G et al. submitted
Nagy G et al. in preparation
Nagy G et al. (2012) Photosynth Res 111:113
Szalontai B et al. in preparation
Neutron scattering in biology - does it have a future?
G Zaccai
CNRS, France
With dedicated instrumentation and first publications appearing in the early 1970s, neutron scattering in biology
has celebrated its fortieth birthday. Is it now overtaken and to be made redundant by powerful developments in
synchrotron radiation and NMR for the study of biological molecular structure and dynamics, or does it still have a
future? The physics of the neutron gives it distinct and complementary advantages over X-rays for diffraction studies
of soft matter at the atomic and molecular level, and over NMR for the measurement of trajectories, which are
directly comparable with molecular dynamics simulations on the picosecond to nanosecond time scale. Practical
aspects associated with obtaining samples of the required amount, however, as well as the relatively small number
of appropriate neutron sources in the world pose serious difficulties for attracting the biology community. Nobuhiro
Go, the Japanese theoretical physicist, who published the first normal mode calculation on a protein, said that a
physicist venturing into protein territory should be aware that whereas “physics is simple and universal”, “proteins
are complex and specific”. With each of the tens of thousands of proteins in a genome posing specific questions
regarding its structure, interactions and dynamics the opportunities for neutron scattering remain immense. I shall
discuss in which of the rapidly developing fields of biology neutron scattering is likely to have the largest impact as
well as how to meet the challenge of outreach to the biological community and access to the facilities.
ICNS 2013 International Conference on Neutron Scattering