| 1. |
- Aili, Daniel, 1977-, et al.
(författare)
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Aggregation-Induced Folding of a de novo Designed Polypeptide Immobilized on Gold Nanoparticles
- 2006
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Ingår i: Journal of the American Chemical Society. - : ACS Publications. - 0002-7863 .- 1520-5126. ; 128:7, s. 2194 -2195
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Tidskriftsartikel (refereegranskat)abstract
- This communication reports the first steps in the construction of a novel, nanoparticle-based hybrid material for biomimetic and biosensor applications. Gold nanoparticles were modified with synthetic polypeptides to enable control of the particle aggregation state in a switchable manner, and particle aggregation was, in turn, found to induce folding of the immobilized peptides.
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| 2. |
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| 3. |
- Aili, Daniel, 1977-, et al.
(författare)
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Assembly of Polypeptide-Functionalized Gold Nanoparticles through a Heteroassociation- and Folding-Dependent Bridging
- 2008
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Ingår i: Nano letters (Print). - : ACS Publications. - 1530-6984 .- 1530-6992. ; 8:8, s. 2473-2478
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Tidskriftsartikel (refereegranskat)abstract
- Gold nanoparticles were functionalized with a synthetic polypeptide, de novo-designed to associate with a charge complementary linker polypeptide in a folding-dependent manner. A heterotrimeric complex that folds into two disulphide-linked four-helix bundles is formed when the linker polypeptide associates with two of the immobilized peptides. The heterotrimer forms in between separate particles and induces a rapid and extensive aggregation with a well-defined interparticle spacing. The aggregated particles are redispersed when the disulphide bridge in the linker polypeptide is reduced.
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| 4. |
- Aili, Daniel, 1977-, et al.
(författare)
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Colorimetric Protein Sensing by Controlled Assembly of Gold Nanoparticles Functionalized with Synthetic Receptors
- 2009
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 5:21, s. 2445-2452
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Tidskriftsartikel (refereegranskat)abstract
- A novel strategy is described for the colorimetric sensing of proteins, based on polypeptide-functionalized gold nanoparticles. Recognition is accomplished using a polypeptide sensor scaffold designed to specifically bind to the model analyte, human carbonic anhydrase II (HCAII). The extent of particle aggregation, induced by the Zn2+-triggered dimerization and folding of a second polypeptide also present on the surface of the gold nanoparticle, gives a readily detectable colorimetric shift that is dependent on the concentration of the target protein. In the absence of HCAII, particle aggregation results in a major redshift of the plasmon peak, whereas analyte binding prevented the formation of dense aggregates, significantly reducing the magnitude of the redshift. The versatility of the technique is demonstrated using a second model system based on the recognition of a peptide sequence from the tobacco mosaic virus coat protein (TMVP) by a recombinant antibody fragment (Fab57P). Concentrations down to approximate to 10 nM and approximate to 25 nM are detected for HCAII and Fab57P, respectively. This strategy is proposed as a generic platform for robust and specific protein analysis that can be further developed to monitor a wide range of target proteins.
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| 5. |
- Aili, Daniel, et al.
(författare)
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Colorimetric sensing: Small 21/2009
- 2009
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Ingår i: Small. - : John Wiley & Sons. - 1613-6810 .- 1613-6829. ; 5:21
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The cover picture illustrates a novel concept for colorimetric protein sensing based on the controllable assembly of polypeptide-functionalized gold nanoparticles. Recognition of the analyte is accomplished by polypeptide-based synthetic receptors immobilized on gold nanoparticles. Also present on the particle surface is a de novo-designed helix-loop-helix polypeptide that homodimerizes and folds into four-helix bundles in the presence of Zn2+, resulting in particle aggregation. Analyte binding interferes with the folding-induced aggregation, giving rise to a clearly detectable colorimetric response.
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| 6. |
- Aili, Daniel, 1977-, et al.
(författare)
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Controlled Assembly of Gold Nanoparticles using De Novo Designed Polypeptide Scaffolds
- 2008
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Ingår i: Proceedings SPIE, Vol. 6885, Photonic Biosensing and Microoptics. - : SPIE. ; , s. 688506-1-688506-8
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Konferensbidrag (refereegranskat)abstract
- Heterodimerization between designed helix-loop-helix polypeptides was utilized in order to assemble gold nanoparticles on planar substrates. The peptides were designed to fold into four-helix bundles upon dimerization. A Cys-residue in the loop region was used to immobilize one of the complementary peptides on a maleimide containing SAM on planar gold substrates whereas the second peptide was immobilized directly on gold nanoparticles. Introducing the peptide decorated particles over a peptide functionalized surface resulted in particle assembly. Further, citrate stabilized particles were assembled on amino-silane modified glass and silicon substrates. By subsequently introducing peptides and gold nanoparticles, particle-peptide hybrid multi layers could be formed.
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| 7. |
- Aili, Daniel, 1977-, et al.
(författare)
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Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles
- 2008
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 130:17, s. 5780-5788
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Tidskriftsartikel (refereegranskat)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.
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| 8. |
- Aili, Daniel, 1977-
(författare)
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Polypeptide-Based Nanoscale Materials
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Self-assembly has emerged as a promising technique for fabrication of novel hybrid materials and nanostructures. The work presented in this thesis has been focused on developing nanoscale materials based on synthetic de novo designed polypeptides. The polypeptides have been utilized for the assembly of gold nanoparticles, fibrous nanostructures, and for sensing applications.The 42-residue polypeptides are designed to fold into helix-loop-helix motifs and dimerize to form four-helix bundles. Folding is primarily driven by the formation of a hydrophobic core made up by the hydrophobic faces of the amphiphilic helices. The peptides have either a negative or positive net charge at neutral pH, depending on the relative abundance of Glu and Lys. Charge repulsion thus prevents homodimerization at pH 7 while promoting hetero-dimerization through the formation of stabilising salt bridges. A Cys incorporated in position 22, located in the loop region, allowed for directed, thiol-dependent, immobilization on planar gold surfaces and gold nanoparticles. The negatively charged (Glu-rich) peptide formed homodimers and folded in solution at pH < 6 or in the presence of certain metal ions, such as Zn2+. The folding properties of this peptide were retained when immobilized directly on gold, which enabled reversible assembly of gold nanoparticles resulting in aggregates with well-defined interparticle separations. Particle aggregation was found to induce folding of the immobilized peptides but folding could also be utilized to induce aggregation of the particles by exploiting the highly specific interactions involved in both homodimerization and hetero-association. The possibility to control the assembly of polypeptide-functionalized gold nanoparticles was utilized in a colorimetric protein assay. Analyte binding to immobilized ligands prevented the formation of dense particle aggregates when subjecting the particles to conditions normally causing extensive aggregation. Analyte binding could hence easily be distinguished by the naked eye. Moreover, the peptides were utilized to assemble gold nanoparticles on planar gold and silica substrates.Fibrous nanostructures were realized by linking monomers through a disulphide-bridge. The disulphide-linked peptides were found to spontaneously assemble into long and extremely thin peptide fibres as a result of a propagating association mediated by folding into four-helix bundles.
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