title: Enhanced stiffness of silk-like fibers by loop formation in the corona leads to stronger gels.
abstract: We study the self-assembly of protein polymers consisting of a silk-like block flanked by two hydrophilic blocks, with a cysteine residue attached to the C-terminal end. The silk blocks self-assemble to form fibers while the hydrophilic blocks form a stabilizing corona. Entanglement of the fibers leads to the formation of hydrogels. Under oxidizing conditions the cysteine residues form disulfide bridges, effectively connecting two corona chains at their ends to form a loop. We find that this leads to a significant increase in the elastic modulus of the gels. Using atomic force microscopy, we show that this stiffening is due to an increase of the persistence length of the fibers. Self-consistent-field calculations indicate a slight decrease of the lateral pressure in the corona upon loop formation. We argue that this small decrease in the repulsive interactions affects the stacking of the silk-like blocks in the core, resulting in a more rigid fiber.
authors.affiliation: Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, Wageningen, NL-6708 WE, The Netherlands.
authors.forename: Wolf H
authors.initials: WH
authors.lastname: Rombouts
authors.affiliation: Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, Wageningen, NL-6708 WE, The Netherlands.|Wageningen UR Food & Biobased Research, Bornse Weilanden 9, Wageningen, NL-6708 WG, The Netherlands.
authors.forename: Natalia E
authors.initials: NE
authors.lastname: Domeradzka
authors.affiliation: Wageningen UR Food & Biobased Research, Bornse Weilanden 9, Wageningen, NL-6708 WG, The Netherlands.
authors.forename: Marc W T
authors.initials: MW
authors.lastname: Werten
authors.affiliation: Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, Wageningen, NL-6708 WE, The Netherlands.
authors.forename: Frans A M
authors.initials: FA
authors.lastname: Leermakers
authors.affiliation: Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, Wageningen, NL-6708 WE, The Netherlands.
authors.forename: Renko J
authors.initials: RJ
authors.lastname: de Vries
authors.affiliation: Wageningen UR Food & Biobased Research, Bornse Weilanden 9, Wageningen, NL-6708 WG, The Netherlands.
authors.forename: Frits A
authors.initials: FA
authors.lastname: de Wolf
authors.affiliation: Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, Wageningen, NL-6708 WE, The Netherlands.
authors.forename: Jasper
authors.initials: J
authors.lastname: van der Gucht
mesh_terms: D003545:Cysteine / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D047011:Silk / Q000737:chemistry*
chemical_list: D004220:Disulfides; D047011:Silk; D003545:Cysteine
keywords: fibers; hydrogels; protein polymers; rheology; self-assembly