title: Interaction of apo cytochrome c with sulfonated polystyrene nanoparticles.
abstract: Stable nanoparticle dispersion in aqueous solutions was obtained with partially sulfonated polystyrene. The hydrophobic association of the backbone chains and phenyl groups is balanced by the electrostatic repulsion of the sulfonate groups on the particle surface. The size distribution of the sulfonated polystyrene particles in relation to concentration, degree of sulfonation and chain length, and pH was characterized by dynamic laser light-scattering. The structure and morphology of the particles were characterized with fluorescence and atom force microscopy. Highly sulfonated polystyrene particles can form large complex particles with positively charged protein, apo cytochrome c. Dynamic laser light-scattering and atom force microscopy studies show that the size and distribution of the complex particles depend on the relative amount of apo cytochrome c and sulfonated polystyrene. When sulfonated polystyrene is in excess, apo cytochrome c interacts with sulfonated polystyrene particles forming stable complexes and excessive sulfonated polystyrene particles bind to the periphery of the complexes preventing them from further aggregation. When apo cytochrome c is in excess, apo cytochrome c links the complexes forming much larger particles. Fluorescence study demonstrates that the hydrophobicity/hydrophility of the complex particles is relative to the ratio of apo cytochrome c and sulfonated polystyrene, degree of sulfonation, and pH. Apo cytochrome c not only can neutralize the negative charges on the surface of sulfonated polystyrene particles, but may also insert into the cores disrupting the original structure of sulfonated polystyrene particles.
authors.affiliation: Department of Macromolecular Science and the Key Laboratory of Molecular Engineering of Polymer, Fudan University, Shanghai 200433, China.
authors.forename: Li
authors.initials: L
authors.lastname: Liang
authors.forename: Ping
authors.initials: P
authors.lastname: Yao
authors.forename: Jie
authors.initials: J
authors.lastname: Gong
authors.forename: Ming
authors.initials: M
authors.lastname: Jiang
mesh_terms: D001059:Apoproteins / Q000737:chemistry*; D045304:Cytochromes c / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D009994:Osmolar Concentration; D011137:Polystyrenes / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D001059:Apoproteins; D011137:Polystyrenes; C071389:polystyrene sulfate; D045304:Cytochromes c