Probing the Structure and Dynamics of Cells, Cell Components and Endogenous Nanoparticles Under Extreme Conditions with Neutrons
Biological cells are fascinating systems of inconceivable complexity, which fulfil various functions. Among others, cells are able to execute motions, to produce heat, to breathe, to subsist, to grow wand proliferate and to die. Science aims at deciphering the different functionalities and activities of, and inside, the cells and how their different components participate to them. The methods employed are also versatile, as optical approaches by microscopies, modelling and simulations, spectroscopies, thermodynamic measurements and much more, each procuring some pieces of the puzzle. Although the different investigations are laborious and time consuming, research is the only way to disentangle the world at the microscopic level surrounding us. In the present study, we cite a few examples of studies on whole cells and cell components by different neutron scattering techniques to illustrate the modern possibilities. As neutrons are not charged, they have interactions directly with the atomic nuclei and give access to structural as well as dynamical information through coherent and incoherent neutron scattering. These techniques can be applied to the same samples and under identical experimental conditions so that we can gain knowledge on the correlations between structural and dynamical functions. Here, we present applications of neutron experiments to decipher the behaviour of complex biological samples, which study was not possible by other probes. The first example focuses on the molecular basis of the adaptation of cells living under extreme conditions, such as Archaea from the deep sea hydrothermal vents which experience both high temperature and high pressure stresses. Molecular dynamics seems to play a key role for adaptation as it is increased for the proteome of cells from such environment, in contrast to common expectation. In the second example, we exposed endogenous nanoparticles, low density lipoproteins, to high hydrostatic pressure, to shed light on the flexibility and stability of such particles under extreme conditions. Here we found that the native particle was surprisingly resistant to pressure application, concerning both dynamics and structure, while a modified form thereof was not.
This work has been supported by the Austrian Science Fund (FWF Project No. I 1109-N28 to R. P.) and by two projects financed by the Agence Nationale de la Recherche (ANR; project number ANR 2010 BLAN 1725 01 Living deep and project number ANR-12-ISV5-0002-01 LDLPRESS to J.P.). We thank the ILL for allocation of beamtime and the SANE group of ILL for their support to develop the HHP equipment and C. Payre and J. Maurice for their help to perform the experiments. The work is partially based on experiments performed at the Swiss spallation neutron source SINQ, Paul Scherrer Institute, Villigen, Switzerland. The work benefitted from SasView software, originally developed by the DANSE project under NSF award DMR-0520547. We are gratefully acknowledging the help of the local contacts on the various instruments, in particular B. Frick, M. M. Koza, J. Ollivier, J. Kohlbrecher and G. Nagy. We wish to thank our many co-workers for their help and fruitful discussions, in particular N. Martinez, G. Michoud, A. Cario, B. Franzetti, M. Jebbar, B. Lehofer and M. Golub.
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