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Abstract : The mechanisms driving the formation of complexes made of charged polymeric chains (polyelectrolytes) and proteins, found in domains such as food engineering, pharmacology, or biology, lead to structures still poorly known. We studied them by Small Angle Neutron Scattering (SANS) and used deuterated polymer and contrast matching in solvents made of heavy water and light water. The protein is the lysozyme (positively charged at pH<11) and the polyelectrolyte is polystyrene sulfonate (PSS, always negatively charged). The ratio of
charges brought ([-]/[+]) is an essential parameter. When it is close to 1, two structures can be obtained. One is a gel of PSS crosslinked by the proteins that locally shrink the PSS chains but keep them in an entangled regime (semi-diluted). The other is made of dense globules (radius ~10 nm) with a fractal organisation at higher scale where the chains are too short and are in a disentangled regime (diluted) after being shrunk. This structure is very well defined and allows a deeper study: we have shown that the core of the globules has a null charge, that the species in excess in an electrostatic point of view stay in solution, possibly in a shell for the PSS chains, and that their size is fixed by the ionic strength. A specific measurement of the counterions has proved that they are ejected from the core of the complexes during their formation. The conformation of the chains inside the complexes has been measured using an adapted labelling. Finally when [-]/[+]>>1, a fluid and limpid transient network of proteins denatured by the PSS is obtained.
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Contributor : Jérémie Gummel <>
Submitted on : Thursday, December 14, 2006 - 11:13:21 AM
Last modification on : Thursday, July 8, 2021 - 3:49:36 AM
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  • HAL Id : tel-00120315, version 1



Jérémie Gummel. STRUCTURES ET MECANISMES DE FORMATION DE COMPLEXES POLYELECTROLYTE-PROTEINE. Analyse de données, Statistiques et Probabilités []. Université Paris Sud - Paris XI, 2006. Français. ⟨tel-00120315⟩



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