Systematically controlling the assembly architecture within a class of chiral nanoparticle superstructures is important for fine-tuning their chiroptical properties. Here, we report a family of ...chiral gold nanoparticle single helices, varying in helical pitch and nanoparticle dimensions, that is assembled using a series of peptide conjugate molecules C x -(PEPAu M‑ox)2 (PEPAu M‑ox = AYSSGAPPMoxPPF; x = 16–22). We demonstrate that the aliphatic tail length (i) can be used as a handle to systematically tune the helical pitch from 80 to 130 nm; and (ii) influences the size, shape, and aspect ratio of the component nanoparticles. Certain members of this family of materials exhibit intense plasmonic chiroptical activity. These studies highlight the multiple levels of structural control that can be achieved within a class of chiral nanoparticle superstructures via careful design and selection of peptide conjugate precursor.
Crystalline 3-D materials bearing interlinked domains of differential porosity and functionality offer the potential for organizing and shuttling molecular and nanoscale matter to specific locations ...within 3-D space. Here, we present methods for creating prototype MOF materials that have such structural features. Specifically, the process of pore expansion via ligand exchange was studied for an isoreticular series of mesoporous MOFs based on bMOF-100. It was found that pore expansion occurs incrementally in small steps and that it proceeds gradually in an “outside→in” fashion within individual crystals. The ligand exchange reaction can be terminated prior to complete crystal conversion to yield intermediate product MOFs, denoted bMOF-100/102 and bMOF-102/106, which bear descending porosity gradients from the crystal periphery to the crystal core. As a proof of concept, size-sensitive incorporation of a gold–thiolate nanocluster, Au133(SR)52, selectively in the bMOF-102/106 crystal periphery region was accomplished via cation exchange. These new methods open up the possibility of controlling molecular organization and transport within porous MOF materials.
Engineering free-standing 2D nanomaterials with compositional, spatial, and functional control across size regimes from the nano- to mesoscale represents a significant challenge. Herein, we ...demonstrate a straightforward strategy for the thermodynamically controlled fabrication of multicomponent sectored nanosheets in which each sector can be chemically and spatially addressed independently and orthogonally. Collagen triple helices, comprising collagen-mimetic peptides (CMPs), are employed as molecularly programmable crystallizable units. Modulating their thermodynamic stability affords the controlled synthesis of 2D core–shell nanostructures via thermally driven heteroepitaxial growth. Structural information, gathered from SAXS and cryo-TEM, reveals that the distinct peptide domains maintain their intrinsic lattice structure and illuminates various mechanisms employed by CMP triple helices to alleviate the elastic strain associated with the interfacial lattice mismatch. Finally, we demonstrate that different sectors of the sheet surface can be selectively functionalized using bioorthogonal conjugation chemistry. Altogether, we establish a robust platform for constructing multifunctional 2D nanoarchitectures in which one can systematically program their compositional, spatial, and functional properties, which is a significant step toward their deployment into functional nanoscale devices.
The successful integration of 2D nanomaterials into functional devices hinges on developing fabrication methods that afford hierarchical control across length scales of the entire assembly. We ...demonstrate structural control over a class of crystalline 2D nanosheets assembled from collagen triple helices. By lengthening the triple helix unit through sequential additions of Pro‐Hyp‐Gly triads, we achieved sub‐angstrom tuning over the 2D lattice. These subtle changes influence the overall nanosheet size, which can be adjusted across the mesoscale size regime. The internal structure was observed by cryo‐TEM with direct electron detection, which provides real‐space high‐resolution images, in which individual triple helices comprising the lattice can be clearly discerned. These results establish a general strategy for tuning the structural hierarchy of 2D nanomaterials that employ rigid, cylindrical structural units.
Nanosheet Engineering: Fine‐tuning of 2D crystalline nanosheets across the sub‐, nano‐, and mesoscale regime was achieved through systematically adjusting the length and stability of collagen triple helices. The results afford broad engineering principles for the design and construction of tailorable 2D nanomaterials assembled from rigid, helical structural motifs such as α‐helices or coiled coils.
The designability of orthogonal coiled coil (CC) dimers, which draw on well‐established design rules, plays a pivotal role in fueling the development of CCs as synthetically versatile ...assembly‐directing motifs for the fabrication of bionanomaterials. Here, we aim to expand the synthetic CC toolkit through establishing a “minimalistic” set of orthogonal, de novo CC peptides that comprise 3.5 heptads in length and a single buried Asn to prescribe dimer formation. The designed sequences display excellent partner fidelity, confirmed via circular dichroism (CD) spectroscopy and Ni‐NTA binding assays, and are corroborated in silico using molecular dynamics (MD) simulation. Detailed analysis of the MD conformational data highlights the importance of interhelical E@g‐N@a interactions in coordinating an extensive 6‐residue hydrogen bonding network that “locks” the interchain Asn‐Asn′ contact in place. The enhanced stability imparted to the Asn‐Asn′ bond elicits an increase in thermal stability of CCs up to ~15°C and accounts for significant differences in stability within the collection of similarly designed orthogonal CC pairs. The presented work underlines the utility of MD simulation as a tool for constructing de novo, orthogonal CCs, and presents an alternative handle for modulating the stability of orthogonal CCs via tuning the number of interhelical E@g‐N@a contacts. Expansion of CC design rules is a key ingredient for guiding the design and assembly of more complex, intricate CC‐based architectures for tackling a variety of challenges within the fields of nanomedicine and bionanotechnology.
A set of orthogonal, de novo coiled coil peptides are established comprising 3.5 heptads in length and a single buried Asn to prescribe dimer formation. The designed sequences display excellent partner fidelity. Interhelical E@g‐N@a interactions coordinate an extensive 6‐residue hydrogen bonding network that keeps the interchain Asn‐Asn′ contact in place.
The fabrication of dynamic, transformable biomaterials that respond to environmental cues represents a significant step forward in the development of synthetic materials that rival their highly ...functional, natural counterparts. Here, we describe the design and synthesis of crystalline supramolecular architectures from charge-complementary heteromeric pairs of collagen-mimetic peptides (CMPs). Under appropriate conditions, CMP pairs spontaneously assemble into either 1D ultraporous (pore diameter >100 nm) tubes or 2D bilayer nanosheets due to the structural asymmetry that arises from heteromeric self-association. Crystalline collagen tubes represent a heretofore unobserved morphology of this common biomaterial. In-depth structural characterization from a suite of biophysical methods, including TEM, AFM, high-resolution cryo-EM, and SAXS/WAXS measurements, reveals that the sheet and tube assemblies possess a similar underlying lattice structure. The experimental evidence suggests that the tubular structures are a consequence of the self-scrolling of incipient 2D layers of collagen triple helices and that the scrolling direction determines the formation of two distinct structural isoforms. Furthermore, we show that nanosheets and tubes can spontaneously interconvert through manipulation of the assembly pH and systematic adjustment of the CMP sequence. Altogether, we establish initial guidelines for the construction of dynamically responsive 1D and 2D assemblies that undergo a structurally programmed morphological transition.
Intrinsically disordered proteins and protein regions (IDPs) are prevalent in all proteomes and are essential to cellular function. Unlike folded proteins, IDPs exist in an ensemble of dissimilar ...conformations. Despite this structural plasticity, intramolecular interactions create sequence-specific structural biases that determine an IDP ensemble's three-dimensional shape. Such structural biases can be key to IDP function and are often measured in vitro, but whether those biases are preserved inside the cell is unclear. Here we show that structural biases in IDP ensembles found in vitro are recapitulated inside human-derived cells. We further reveal that structural biases can change in a sequence-dependent manner due to changes in the intracellular milieu, subcellular localization, and intramolecular interactions with tethered well-folded domains. We propose that the structural sensitivity of IDP ensembles can be leveraged for biological function, can be the underlying cause of IDP-driven pathology or can be used to design disorder-based biosensors and actuators.
The properties of nanoparticle superstructures depend on many factors, including the structural metrics of the nanoparticle superstructure (particle diameter, interparticle distances, etc.). Here, we ...introduce a family of gold-binding peptide conjugate molecules that can direct nanoparticle assembly, and we describe how these molecules can be systematically modified to adjust the structural metrics of linear double-helical nanoparticle superstructures. Twelve new peptide conjugates are prepared via linking a gold-binding peptide, AYSSGAPPMPPF (PEPAu), to a hydrophobic aliphatic tail. The peptide conjugates have 1, 2, or 3 PEPAu headgroups and a C12, C14, C16, or C18 aliphatic tail. The soft assembly of these peptide conjugates was studied using transmission electron microscopy (TEM), atomic force microscopy (AFM), and infrared (IR) spectroscopy. Several peptide conjugates assemble into 1-D twisted fibers having measurable structural parameters such as fiber width, thickness, and pitch that can be systematically varied by adjusting the aliphatic tail length and number of peptide headgroups. The linear soft assemblies serve as structural scaffolds for arranging gold nanoparticles into double-helical superstructures, which are examined via TEM. The pitch and interparticle distances of the gold nanoparticle double helices correspond to the underlying metrics of the peptide conjugate soft assemblies, illustrating that designed peptide conjugate molecules can be used to not only direct the assembly of gold nanoparticles but also control the metrics of the assembled structure.
Triblock peptide-oligonucleotide chimeras (POCs) consisting of peptides and oligonucleotides interlinked by an organic core are presented and their assembly behaviour is investigated. Several factors ...influence POC assembly, resulting in the formation of either vesicles or fibres. Design rules are introduced and used to predict and alter POC assembly morphology.
The successful integration of 2D nanomaterials into functional devices hinges on developing fabrication methods that afford hierarchical control across length scales of the entire assembly. We ...demonstrate structural control over a class of crystalline 2D nanosheets assembled from collagen triple helices. By lengthening the triple helix unit through sequential additions of Pro‐Hyp‐Gly triads, we achieved sub‐angstrom tuning over the 2D lattice. These subtle changes influence the overall nanosheet size, which can be adjusted across the mesoscale size regime. The internal structure was observed by cryo‐TEM with direct electron detection, which provides real‐space high‐resolution images, in which individual triple helices comprising the lattice can be clearly discerned. These results establish a general strategy for tuning the structural hierarchy of 2D nanomaterials that employ rigid, cylindrical structural units.
Nanoschicht‐Engineering: Die Feineinstellung von kristallinen 2D‐Nanoschichten über den sub‐nano‐ und mesoskaligen Maßstab wurde durch die systematische Justierung der Länge und Stabilität von Collagen‐Tipelhelices erreicht. Aus den Ergebnissen lassen sich Prinzipien für die Entwicklung und Konstruktion von maßgeschneiderten 2D‐Nanomaterialien ableiten, die aus starren, helicalen Strukturmotiven wie α‐Helices und gewendelte Spiralen aufgebaut sind.
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