Influence of pressure on proteins structure and dynamics investigated by neutron scattering

Pressure is a physical parameter which influence is widely spread in Earth. Indeed, micro-organisms like Bacillus Licheniformis can live in Deep Ocean until 10 km and they can sustain pressure of about 1000 bar [1]. Multimeric protein subunits association-dissociation phenomena and protein folding and unfolding is also more studied using this unusual parameter. The interest of using high pressure comes for its use in food industries for sterilization process since this procedure has less influence on texture and taste than thermal sterilization. In medicine, high pressure is studied for bio-conservation of blood or other oxygen transporter molecules for exampleSmall angle neutron scattering is a suitable tool to investigate soft matter material: for example, proteins from their native to their fully unfolded state since the technique is not destructive and model based on polymer theory studies can be adapted to characterize the structures. The JCNS at MLZ has a 5000 bar high pressure with sapphire windows especially dedicated for structural investigation of soft matter, and particularly biology, investigated by Small Angle Neutron Scattering. The design is based on the high pressure set up described in Kohlbrecher et al 2007 [2]. The cell will be described and a typical example will be presented.Quasielastic neutron scattering allows to explore at the atomic space scale internal motions of proteins in the pico-second time scale [3,4]. Few neutron scattering studies on biomolecules were performed up to date. The first unfolding study using inelastic neutron scattering was published by Doster et al [5,6]. Other studies have been performed by Appavou et al for BPTI [7] and by Di Bari for Trypsin [8]. We would like to present a series of results as a function of pressure we have obtained with the TOFTOF time of flight quasielastic neutron scattering spectrometer (Garching, Germany).We have built a high pressure cell which can sustain a pressure of 2000 bar. The high transmission, due to the aluminium alloy of the cell, allows us to make a quite accurate observation of the influence of pressure on the translational diffusion and the internal dynamics of haemoglobin.References1. C. Balny, Bull. Soc. Fr. Biophys. 140 10–13 (2003).2. Kohlbrecher, J., et al., Rev. Sci. Instr. 78, 125101, doi: 10.1063/1.2817632 (2007)3. J.A. McCammon, S.C. Harvey, Cambridge University Press, Cambridge, 29 (1988).4. M. Bée, Adam Hilger, Bristol, (1988).5. W. Doster and W. Gebhardt, Chem. Phys. 292, 383-389 (2003).6. W. Doster, R. Gebhardt and A. Soper in: Advances in High Pressure Science and Biotechnology II, Springer, Ed. R. Winter 29 (2003).7. M.-S. Appavou, G. Gibrat, M.-C. Bellissent-Funel, Biochimica et Biophysica Acta 1764 414–423 (2006).8. M. Di Bari, A. Deriu, A. Filabozzi, C. Andreani, A. Di Venere, N. Rosato, Physica B 276–278 510–511 (2000)