Publications by authors named "Raghu Pradeep Narayanan"

Sophisticated statistical mechanics approaches and human intuition have demonstrated the possibility of self-assembling complex lattices or finite-size constructs. However, attempts so far have mostly only been successful in silico and often fail in experiment because of unpredicted traps associated with kinetic slowing down (gelation, glass transition) and competing ordered structures. Theoretical predictions also face the difficulty of encoding the desired interparticle interaction potential with the experimentally available nano- and micrometer-sized particles.

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The combination of multiple orthogonal interactions enables hierarchical complexity in self-assembled nanoscale materials. Here, efficient supramolecular polymerization of DNA origami nanostructures is demonstrated using a multivalent display of small molecule host-guest interactions. Modification of DNA strands with cucurbit[7]uril (CB[7]) and its adamantane guest, yielding a supramolecular complex with an affinity of order 10 m , directs hierarchical assembly of origami monomers into 1D nanofibers.

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Improving the precision and function of encapsulating three-dimensional (3D) DNA nanostructures via curved geometries could have transformative impacts on areas such as molecular transport, drug delivery, and nanofabrication. However, the addition of non-rasterized curvature escalates design complexity without algorithmic regularity, and these challenges have limited the ad hoc development and usage of previously unknown shapes. In this work, we develop and automate the application of a set of previously unknown design principles that now includes a multilayer design for closed and curved DNA nanostructures to resolve past obstacles in shape selection, yield, mechanical rigidity, and accessibility.

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The integration of proteins with DNA nanotechnology would enable materials with diverse applications in biology, medicine, and engineering. Here, we describe a method for the incorporation of bioactive fibronectin domain proteins with DNA nanostructures using two orthogonal coiled-coil peptides. One peptide from each coiled-coil pair is attached to a DNA origami cuboid in a multivalent fashion by attaching the peptides to DNA handles.

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We present here the combination of experimental and computational modeling tools for the design and characterization of protein-DNA hybrid nanostructures. Our work incorporates several features in the design of these nanostructures: (1) modeling of the protein-DNA linker identity and length; (2) optimizing the design of protein-DNA cages to account for mechanical stresses; (3) probing the incorporation efficiency of protein-DNA conjugates into DNA nanostructures. The modeling tools were experimentally validated using structural characterization methods like cryo-TEM and AFM.

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DNA nanotechnology marvels the scientific world with its capabilities to design, engineer, and demonstrate nanoscale shapes. This review is a condensed version walking the reader through the structural developments in the field over the past 40 years starting from the basic design rules of the double-stranded building block to the most recent advancements in self-assembled hierarchically achieved structures to date. It builds from the fundamental motivation of building 3-dimensional (3D) lattice structures of tunable cavities going all the way up to artificial nanorobots fighting cancer.

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Metal nanostructures of chiral geometry interacting with light via surface plasmon resonances can produce tailorable optical activity with their structural alterations. However, bottom-up fabrication of arbitrary chiral metal nanostructures with precise size and morphology remains a synthetic challenge. Here we develop a DNA origami-enabled aqueous solution metallization strategy to prescribe the chirality of silver nanostructures in three dimensions.

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Nature has evolved strategies to encode information within a single biopolymer to program biomolecular interactions with characteristic stoichiometry, orthogonality and reconfigurability. Nevertheless, synthetic approaches for programming molecular reactions or assembly generally rely on the use of multiple polymer chains (for example, patchy particles). Here we demonstrate a method for patterning colloidal gold nanoparticles with valence bond analogues using single-stranded DNA encoders containing polyadenine (polyA).

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We report the first example of a covalently bound dimer of monolayer protected atomically precise silver nanocluster [Ag25(DMBT)18]- (DMBT stands for 2,4-dimethylbenzenethiol). Covalently linked dimers could be important to design new cluster assembled materials with composite properties.

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Three-dimensional (3D) cages are one of the most important targets for nanotechnology. Both proteins and DNA have been used as building blocks to create tunable nanoscale cages for a wide range of applications, but each molecular type has its own limitations. Here, we report a cage constructed from both protein and DNA building blocks through the use of covalent protein-DNA conjugates.

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DNA tile-based assembly provides a promising bottom-up avenue to create designer two-dimensional (2D) and three-dimensional (3D) crystalline structures that may host guest molecules or nanoparticles to achieve novel functionalities. Herein, we introduce a new kind of DNA tiles (named layered-crossover tiles) that each consists of two or four pairs of layered crossovers to bridge DNA helices in two neighboring layers with precisely predetermined relative orientations. By providing proper matching rules for the sticky ends at the terminals, these layered-crossover tiles are able to assemble into 2D periodic lattices with precisely controlled angles ranging from 20° to 80°.

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A three-dimensional luminescent metal-organic framework, {Mg(DHT)(DMF)(2)}(n) (1), based on an excited-state intramolecular proton-transfer (ESIPT) responsive linker, 2,5-dihydroxyterephthalic acid (H(2)DHT), has been synthesized, and its desolvated microporous framework with pendent -OH groups on the pore surface was exploited for the binding and specific sensing of metal ions via Lewis acid-base interactions. The luminescence intensity significantly quenches with Cu(II) among various s- and d-block metal ions, and highly selective sensing of Cu(II) ions has been realized in both solid and solution states (up to nanomolar concentration). The immobilized Cu(II) metal ions can be selectively removed by chelating agents like ethylenediaminetetraacetic acid without any structural disintegration of the framework, as revealed by the luminescence and gas-adsorption studies.

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