Unraveling the origin of chirality from plasmonic nanoparticle-protein complexes

Abstract

Plasmon-coupled circular dichroism has emerged as a promising approach for ultrasensitive detection of biomolecular conformations through coupling between molecular chirality and surface plasmons. Chiral nanoparticle assemblies without chiral molecules present also have large optical activities. We apply single-particle circular differential scattering spectroscopy coupled with electron imaging and simulations to identify both structural chirality of plasmonic aggregates and plasmon-coupled circular dichroism induced by chiral proteins. We establish that both chiral aggregates and just a few proteins in interparticle gaps of achiral assemblies are responsible for the ensemble signal, but single nanoparticles do not contribute. We furthermore find that the protein plays two roles: It transfers chirality to both chiral and achiral plasmonic substrates, and it is also responsible for the chiral three-dimensional assembly of nanorods. Understanding these underlying factors paves the way toward sensing the chirality of single biomolecules.

Chirality Transfer from Sub‐Nanometer Biochemical Molecules to Sub‐Micrometer Plasmonic Metastructures: Physiochemical Mechanisms, Biosensing, and Bioimaging Opportunities

“…On the other hand, special care should be taken when a new CD resonance appears at the plasmon resonance absorption band of a metallic NP coated by or NP assembly connected by chiral biomolecules, because the dipole-dipole interaction induced plasmonic CD could probably be intertwined with the NP structural chirality. [220,221] Let us take a chiral-molecule-linked plasmonic NR dimer as an example: where the two NRs may not reside in the same plane, leading to the occurrence of structural chirality. [222,223] The resultant chiroptical enhancement in such nanostructures therefor could be due to the competition between electromagnetic interaction and structural chirality, [224] which cannot be differentiated by traditional ensemble spectroscopic measurements.…”

Toward Chiral Sensing and Spectroscopy Enabled by All‐Dielectric Integrated Photonic Waveguides

“…Although throughout this work we only focused on the chiroptical behavior of a metallic nanohelix, in real applications this would be extensible to other geometries and materials more relevant, [74][75][76] specifically to chiral molecules. [15] Likewise, taking into account earlier schemes, plasmonic nanostructures, [22] or high-index dielectric nanoparticles, [29] might be added in order to enhance the chiroptical response when a certain substance is applied, [81] thus leading to hybrid chiral plasmonic-photonic systems. Somehow connected with this, it is worth noticing that the chiral structure considered here has only been used as a chiral sample to probe the chiroptical interactions.…”

Directing Arrowhead Nanorod Dimers for MicroRNA In Situ Raman Detection in Living Cells

“…Directed self‐assembly of anisotropic nanoscale building blocks is an efficient strategy for producing diverse superstructures with unique optical properties for technologies applications, [ 1–8 ] especially for plasmonic nanocrystals, as the multiple optical properties are determined by their geometrical arrangement. [ 9–16 ] The key influencing factor in the successful formation of directed diverse assemblies is the anisotropy of nanoscale building blocks originating from the shape and unequal distribution of ligands on the surface of nanocrystals.…”