title: Understanding the self-assembly of proteins onto gold nanoparticles and quantum dots driven by metal-histidine coordination.
abstract: Coupling of polyhistidine-appended biomolecules to inorganic nanocrystals driven by metal-affinity interactions is a greatly promising strategy to form hybrid bioconjugates. It is simple to implement and can take advantage of the fact that polyhistidine-appended proteins and peptides are routinely prepared using well established molecular engineering techniques. A few groups have shown its effectiveness for coupling proteins onto Zn- or Cd-rich semiconductor quantum dots (QDs). Expanding this conjugation scheme to other metal-rich nanoparticles (NPs) such as AuNPs would be of great interest to researchers actively seeking effective means for interfacing nanostructured materials with biology. In this report, we investigated the metal-affinity driven self-assembly between AuNPs and two engineered proteins, a His7-appended maltose binding protein (MBP-His) and a fluorescent His6-terminated mCherry protein. In particular, we investigated the influence of the capping ligand affinity to the nanoparticle surface, its density, and its lateral extension on the AuNP-protein self-assembly. Affinity gel chromatography was used to test the AuNP-MPB-His7 self-assembly, while NP-to-mCherry-His6 binding was evaluated using fluorescence measurements. We also assessed the kinetics of the self-assembly between AuNPs and proteins in solution, using time-dependent changes in the energy transfer quenching of mCherry fluorescent proteins as they immobilize onto the AuNP surface. This allowed determination of the dissociation rate constant, Kd(-1) ∼ 1-5 nM. Furthermore, a close comparison of the protein self-assembly onto AuNPs or QDs provided additional insights into which parameters control the interactions between imidazoles and metal ions in these systems.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University , 95 Chieftan Way, Tallahassee, Florida 32306, United States.
authors.forename: Fadi
authors.initials: F
authors.lastname: Aldeek
authors.forename: Malak
authors.initials: M
authors.lastname: Safi
authors.forename: Naiqian
authors.initials: N
authors.lastname: Zhan
authors.forename: Goutam
authors.initials: G
authors.lastname: Palui
authors.forename: Hedi
authors.initials: H
authors.lastname: Mattoussi
mesh_terms: D002104:Cadmium / Q000737:chemistry; D002846:Chromatography, Affinity; D006046:Gold / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D053768:Metal Nanoparticles / Q000737:chemistry*; D008670:Metals; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods; D010455:Peptides / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D045663:Quantum Dots; D012666:Semiconductors; D013438:Sulfhydryl Compounds; D015032:Zinc / Q000737:chemistry
chemical_list: D007093:Imidazoles; D008024:Ligands; D008670:Metals; D010455:Peptides; D011506:Proteins; D013438:Sulfhydryl Compounds; D002104:Cadmium; C033223:polyhistidine; D006639:Histidine; D006046:Gold; D015032:Zinc