title: Folding induced assembly of polypeptide decorated gold nanoparticles.
abstract: Reversible assembly of gold nanoparticles controlled by the homodimerization and folding of an immobilized de novo designed synthetic polypeptide is described. In solution at neutral pH, the polypeptide folds into a helix-loop-helix four-helix bundle in the presence of zinc ions. When immobilized on gold nanoparticles, the addition of zinc ions induces dimerization and folding between peptide monomers located on separate particles, resulting in rapid particle aggregation. The particles can be completely redispersed by removal of the zinc ions from the peptide upon addition of EDTA. Calcium ions, which do not induce folding in solution, have no effect on the stability of the peptide decorated particles. The contribution from folding on particle assembly was further determined utilizing a reference peptide with the same primary sequence but containing both D and L amino acids. Particles functionalized with the reference peptide do not aggregate, as the peptides are unable to fold. The two peptides, linked to the nanoparticle surface via a cysteine residue located in the loop region, form submonolayers on planar gold with comparable properties regarding surface density, orientation, and ability to interact with zinc ions. These results demonstrate that nanoparticle assembly can be induced, controlled, and to some extent tuned, by exploiting specific molecular interactions involved in polypeptide folding.
authors.affiliation: Division of Sensor Science and Molecular Physics, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden.
authors.forename: Daniel
authors.initials: D
authors.lastname: Aili
authors.forename: Karin
authors.initials: K
authors.lastname: Enander
authors.forename: Johan
authors.initials: J
authors.lastname: Rydberg
authors.forename: Irina
authors.initials: I
authors.lastname: Nesterenko
authors.forename: Fredrik
authors.initials: F
authors.lastname: Björefors
authors.forename: Lars
authors.initials: L
authors.lastname: Baltzer
authors.forename: Bo
authors.initials: B
authors.lastname: Liedberg
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D002413:Cations, Divalent; D002942:Circular Dichroism; D019281:Dimerization; D004492:Edetic Acid / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D015032:Zinc / Q000737:chemistry
chemical_list: D000596:Amino Acids; D002413:Cations, Divalent; D009842:Oligopeptides; D006046:Gold; D004492:Edetic Acid; D015032:Zinc