Optical Control of Nanoparticle Catalysis Influenced by Photoswitch Positioning in Hybrid Peptide Capping Ligands

Abstract

Here, we present an in-depth analysis of structural factors that modulate peptide-capped nanoparticle catalytic activity via optically driven structural reconfiguration of the biointerface present at the particle surface. Six different sets of peptide-capped Au nanoparticles were prepared, in which an azobenzene photoswitch was incorporated into one of two well-studied peptide sequences with known affinity for Au, each at one of three different positions: the N- or C-terminus or mid-sequence. Changes in the photoswitch isomerization state induce a reversible structural change in the surface-bound peptide, which modulates the catalytic activity of the material. This control of reactivity is attributed to changes in the amount of accessible metallic surface area available to drive the reaction. This research specifically focuses on the effect of the peptide sequence and photoswitch position in the biomolecule, from which potential target systems for on/off reactivity have been identified. Additionally, trends associated with photoswitch position for a peptide sequence (Pd4) have been identified. Integrating the azobenzene at the N-terminus or central region results in nanocatalysts with greater reactivity in the trans and cis conformations, respectively, however, positioning the photoswitch at the C-terminus gives rise to a unique system that is reactive in the trans conformation and partially deactivated in the cis conformation. These results provide a fundamental basis for new directions in nanoparticle catalyst development to control activity in real time, which could have significant implications in the design of catalysts for multistep reactions using a single catalyst. Additionally, such a fine level of interfacial structural control could prove to be important for applications beyond catalysis, including biosensing, photonics, and energy technologies that are highly dependent on particle surface structures.

Modulation of Peptide–Graphene Interfaces via Fatty Acid Conjugation

“…For example, the attachment of azobenzene groups to Au‐binding peptides was recently demonstrated to create photostimulated reconfiguration of biotic/abiotic interfaces based on peptide‐capped Au nanoparticles [ 5 ] with optically switchable catalytic properties. [ 6 ] Attachment of aliphatic molecules to Au‐binding peptides has proven to be useful for controlling Au‐based nanoparticle growth and organization [ 7 ] for producing materials with enhanced chiroptical properties. [ 8 ] Fatty acid/peptide conjugates have also been recently reported as useful agents for exfoliation of graphite into graphene sheets in aqueous media.…”

Optical Control of Biomimetic Nanoparticle Catalysts Based upon the Metal Component

“…Changes in the photoswitch isomerization state, and thus the peptide overlayer structure, are known to directly influence the reaction rates. 5,24 This has been largely attributed to substrate accessibility to reaction sites along the metallic NP surface. Because the metal of the particle plays a direct role in controlling peptide conformation when bound, changes in the reactivity based upon the NP metal through its effect on the ligand conformation are possible, along with the direct effects of the catalytic metal.…”

“…5,10 Further studies have demonstrated that additional factors such as the peptide sequence and photoswitch position are critical in determining catalytic activity changes as a function of the peptide overlayer morphology for Au NPs. 24 While the inorganic NP composition clearly affects the catalytic activity, it is also known to have dramatic implications on photoswitchable peptide reconfiguration. 12,25,26 Here, we study the behavior of these optically triggered peptides across different metallic interfaces.…”

“…These changes in the isomerization state alter the affinity of the biomolecule for the metallic surface and can be used to optically tune the final size of the NP. , Photoisomerization can also be accomplished using nonlinear optical approaches under specific conditions . The catalytic properties of NPs capped with photoswitchable peptides are sensitive to isomerization-based structural changes and can be varied between two different reaction regimes based upon the reversible peptide conformation. , Further studies have demonstrated that additional factors such as the peptide sequence and photoswitch position are critical in determining catalytic activity changes as a function of the peptide overlayer morphology for Au NPs …”

Photoswitchable Catalysis Mediated by Nanoparticles

“…Subsequent studies [14b] gave more insight into the influence of azobenzene position in peptide and introduced another peptide (named Pd4) with affinity to the gold surface. Three derivatives were obtained by introduction of azobenzene moiety to N‐terminus (named CAuBP1 and CPd4), C‐terminus (named AuBP1C and Pd4C) and in the middle of the peptides chains (named AuBP1[C] and Pd4[C]).…”