ORIGINAL PAPER Temperature dependence of protein dynamics as affected by sugars: a neutron scattering study S. Magazu ` Æ G. Romeo Æ M. T. F. Telling Received: 5 February 2007 / Revised: 29 April 2007 / Accepted: 7 May 2007 / Published online: 27 July 2007 Ó EBSA 2007 Abstract Neutron scattering data on lysozyme–trehalose and lysozyme–sucrose aqueous mixtures, and on trehalose and sucrose aqueous mixtures are presented for a wide temperature range. Although the degree of protein coupling to solvent seems to be an open question in the literature, we present evidence that seems to be a firm link between a local dynamics of the protein with that of the glassy host. One of the objectives of this study was to explore the relationship between protein dynamics and glassy host. Measuring the <u 2 > of lysozyme mixtures, we arrive at a qualitative description of how their thermal stability is affected by the presence of two sugars at different temperatures. Whereas the Q dependence of the elastic incoherent structure factor gives information about the geometry and the amplitudes of the motions. Introduction The evidence for stabilizing effects of sugars has led to their routine usage in formulating biopharmaceuticals in order to improve their long-term storage and delivery (Pestrelski et al. 1993; Remmele et al. 1997; Shamblin et al. 1999; Hancock and Zografi 1997; Franks et al. 1991). The degree of change in thermal stability was dependent on the type of excipient. Our studies are in the framework of the relations structure–dynamics–function of biological macromolecules, and deal with the temperature dependent transition in the dynamic behaviour of proteins, with ces- sation of anharmonic motions below this temperature. It is generally accepted that proteins require internal flexibility for their activity. The movements required are relatively poorly characterised. Of particular interest are the role in activity of the fast (i.e., picosecond time-scale) fluctuations and to what extent they are coupled to the structural changes, which may take place on time-scales several orders of magnitude slower. Some protein functions have been observed to cease with the loss of equilibrium an- harmonic dynamics as the proteins are cooled through the dynamic transition (Ferrand et al. 1993; Rasmussen et al. 1992; Doster et al. 1989). Incoherent neutron scattering experiments provide information on the motion of the sample hydrogen atoms in a specific time and space window, given by the energy resolution and scattering vector modulus, Q, range. Because the scattering is ‘‘incoherent’’, the sample need not be crystalline or even monodisperse. The glassy mixture, which shows suppressed local dynamics also show enhanced protein stabilization. Cor- done (1999) found that trehalose suppressed the mean square displacement, msd, <u 2 >, in myoglobin significantly in comparison to an aqueous environment. This led them and others (Zaccai 2000) to speculate that an effective lyophilization medium will suppress fast dynamics of the protein reflected in <u 2 >. The implication that a suppres- sion of local motions <u 2 > of a glassy host also indicate a suppression of similar motions of a protein located in that host assumes that the fast, local dynamics of the protein Proceedings of the XVIII Congress of the Italian Society of Pure and Applied Biophysics (SIBPA), Palermo, Sicily, September 2006. S. Magazu `  G. Romeo (&) Physics Department and INFM, Messina University, Messina 98166, Italy e-mail: gio.romeo@tiscali.it M. T. F. Telling ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, UK 123 Eur Biophys J (2007) 36:685–691 DOI 10.1007/s00249-007-0190-y