title: Distinguishing the monomer to cluster phase transition in concentrated lysozyme solutions by studying the temperature dependence of the short-time dynamics.
abstract: Recent combined experiments by small angle neutron scattering (SANS) and neutron spin echo (NSE) have demonstrated that dynamic clusters can form in concentrated lysozyme solutions when the right combination of a short-ranged attraction and a long-ranged electrostatic repulsion exists. In this paper, we investigate the temperature effect on the dynamic cluster formation and try to pinpoint the transition concentration from a monomeric protein phase to a cluster phase. Interestingly, even at a relatively high concentration (10% mass fraction), despite the significant change in the SANS patterns that are associated with the change of the short-ranged attraction among proteins, the normalized short-time self-diffusion coefficient is not affected between 5 and 40 °C. This is interpreted as a lack of cluster formation in this condition. However, at larger concentrations such as 17.5% and 22.5% mass fraction, we show that the average hydrodynamic radius increases significantly and causes a large decrease of the normalized self-diffusion coefficient as a result of cluster formation when the temperature is changed from 25 to 5 °C.
authors.affiliation: Institut Laue-Langevin, BP 156, F-38042 Grenoble CEDEX 9, France.
authors.forename: Péter
authors.initials: P
authors.lastname: Falus
authors.forename: Lionel
authors.initials: L
authors.lastname: Porcar
authors.forename: Emiliano
authors.initials: E
authors.lastname: Fratini
authors.forename: Wei-Ren
authors.initials: WR
authors.lastname: Chen
authors.forename: Antonio
authors.initials: A
authors.lastname: Faraone
authors.forename: Kunlun
authors.initials: K
authors.lastname: Hong
authors.forename: Piero
authors.initials: P
authors.lastname: Baglioni
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu