A taste of Neutrons in Food

Susana C.M. Teixeira

Over 30% of proteins studied by neutron crystallography are either an ingredient or have direct applications in food industry [1]. The rapid growth of the number of the neutron crystal structures deposited in the PDB database is not diluting this bias. Applications of neutron crystallography are nonetheless clearly expanding to a range of areas (e.g. Bioenergy), enabled by advances in instrumentation, software and complementary techniques [2-3]. Two food-related examples will be presented, highlighting the structural and dynamic information that neutrons can probe on a variety of macromolecules.

Neutron studies [4-5] on sweet proteins will be described. Extensive structural data from other techniques has failed to provide a common molecular basis for thaumatin and monellin, the sweetest compounds known to man. Insights into the mechanism of sweet taste are hindered by the lack of experimental structural data on the corresponding receptor. Preliminary neutron crystallographic studies focused on properties of the proteins under conditions relevant to physiological processes, food storage and processing. An integrative approach through a combination of small angle scattering and crystallographic studies of isotope-labelled samples can tackle the protein receptor-interaction.

The second example will focus on Osteopontin (OPN), a protein present in human milk and an important ingredient in infant formula. OPN was previously referred to as the "molecule for all seasons" [6], due to its diversity of roles in biomineralisation, immunity, inflammation and cancer. The ability of OPN to prevent ectopic calcification, namely by stabilising calcium phosphate in supersaturated milk and other body fluids, was investigated. Neutron diffraction and scattering, elastic incoherent neutron scattering and other techniques were deployed to study nanoclusters of Osteopontin peptides with calcium phosphate. The results will be discussed [7-8].

[1] S.C.M.Teixeira (2012). Neutron News 23(2), 19-21.
[2] Teixeira, S. et al. (2008). Chem. Phys. 345, 133-151.
[3] Casadei et al. (2014). Science 345, 6193, 193-197.
[4] Teixeira et al. (2010). Acta Cryst. D66 (11), 1139-1143.
[5] Teixeira et al. (2008). Acta Cryst. F64, 378-381.
[6] Mazzali et al. (2002). Q. J. Med. 95, 3-13.
[7] Holt et al. (2014). J. Struct. Biology, 185(3), 383-96.
[8] Lenton et al. (2014). Dairy Science and Technology DOI 10.1007/s13594-014-0177-2.

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