Name: self-assembly of complex two-dimensional shapes from single-stranded dna tiles
Uploaded: 2015-05-08T13:00:00
Description: Watch this Scientific Journal Video about Self-assembly of Complex Two-dimensional Shapes from Single-stranded DNA Tiles at JoVE.com

This work was funded by the Office of Naval Research Young Investigator Program Award N000141110914, Office of Naval Research Grant N000141010827, NSF CAREER Award CCF1054898, NIH Director&#8217;s New Innovator Award 1DP2OD007292 and a Wyss Institute for Biologically Inspired Engineering Faculty Startup Fund (to P.Y.) and Tsinghua-Peking Center for Life Sciences Startup Fund (to B. W.).

1. DNA Sequence Design
<ol>
	<li>Use UNIQUIMER software27 to design a SST-finite structure by specifying the number of double helices, lengths of top and bottom helix for each double helix, and the crossover pattern to create a 24H &#215; 28T canvas. After defining these parameters, the overall architecture (strand composition and the complementarity arrangement) is illustrated graphically&#160;in the program.</li>
	<li>Generate sequences for the strands of the specified structure to meet the complementarity...

<ol>
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In the structure formation step, it is important to keep an appropriate concentration of magnesium cations (e.g., 15 mM) in the DNA strand mixture to self-assemble DNA nanostructures. Similarly, in the agarose gel characterization/purification step, it is important to keep an appropriate magnesium cation concentration (e.g., 10 mM) in the gel and the gel running buffer to retain the DNA nanostructures during electrophoresis. For the 24H&#215;28T rectangle structure, we tested annealing in different Mg<s...

Previous nucleic acid self-assembly work1-25 has led to the successful construction of a variety of complex structures, including DNA2&#8211;5,8,10&#8211;13,17,23 or RNA7,22 periodic3,4,7,22 and algorithmic5 two-dimensional lattices, ribbons10,12 and tubes4,12,13, 3D crystals17, polyhedra11 and finite, 2D shapes7,8. A particularly effective method is scaffolded DNA origami, whereby a single scaffold strand is folded by many short auxiliary staple strands to form a complex shape9,14&#8211;16,18&#8211;21,25.
We recently reported a method for constructing discrete nanostructures with prescribed 2D shapes using single-stranded tiles (SST), and demonstrated structures with complexity comparable to DNA origami26. This article is an adaptation of our earlier work26 and describes detailed protocols for arranging individually addressable SSTs into sophisticated finite 2D shapes with precisely prescribed dimensions (widths and lengths) and morphologies. One key advantage of the SST method is its modularity. Every component SST of a structure serves as a modular construction unit in the assembly, and different subsets of these SSTs produce distinct shapes. Thus, we established a general platform to construct nanostructures with prescribed sizes and shapes from short, synthetic DNA strands.
SSTs contain four domains, each 10 or 11 nucleotides long (Figure 1A). The SSTs bind such that their parallel helices create a DNA lattice held together by crossover linkages. Each crossover is the phosphate between domains 2 and 3. The phosphate is stretched artificially in the diagrams for visual clarity. The crossovers are spaced two helical turns (21 bases) apart (Figure 1B). The composite rectangles are referred to by their dimensions in the number of helices and helical turns. For example, a rectangle that is six helices wide and eight helical turns long is referenced as a 6H &#215; 8T rectangle. SSTs can be left out, added, or otherwise rearranged to create structures of arbitrary shapes and sizes (Figure 1C). For instance, a rectangular design can be rolled into a tube with a desired length and radius (Figure 1D).
Alternatively, the rectangular SST lattice can be viewed as a molecular canvas made up of SST pixels, each 3 nm by 7 nm. In this study, we use a molecular canvas of 310 full-length internal SSTs, 24 full-length SSTs making up the left and right boundaries, and 28 half-length SSTs forming the top and bottom boundaries. The canvas has 24 double helices linked by crossovers and each helix contains 28 helical turns (294 bases) and is therefore referred to as a 24H &#215; 28T rectangular canvas. The 24H &#215; 28T canvas has a molecular weight similar to that of a DNA origami structure created from an M13 phage scaffold.

<table border="0" cellpadding="0" cellspacing="0" width="919">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:183px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:401px;">Comments/Description</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">DNA Strands&#160;</td>
			<td style="width:183px;">Integrated DNA Technology</td>
			<td style="width:119px;"></td>
			<td>Section 3.1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">SYBR Safe DNA gel stain</td>
			<td style="width:183px;">Invitrogen</td>
			<td style="width:119px;">S33102</td>
			<td>Section 3.4.2</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Freeze&#39;N Squeeze DNA Gel Extraction Spin Columns</td>
			<td style="width:183px;">BIO-RAD</td>
			<td style="width:119px;">731-6166</td>
			<td>Section 3.6</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Bruker&#39;s Sharp Nitride Lever Probes</td>
			<td style="width:183px;">Bruker AFM Probes</td>
			<td style="width:119px;">SNL10</td>
			<td>Section 4.3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Safe Imager 2.0 Blue Light Transilluminator</td>
			<td style="width:183px;">Invitrogen</td>
			<td style="width:119px;">G6600</td>
			<td>Section 3.6</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Centrifuge 5430R</td>
			<td style="width:183px;">Eppendorf</td>
			<td style="width:119px;">5428 000.414</td>
			<td>Section 3.6</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Transmission Electron Microscope&#160;</td>
			<td style="width:183px;">Jeol</td>
			<td style="width:119px;">Jem 1400</td>
			<td>Section 7.4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Multimode 8</td>
			<td style="width:183px;">Veeco</td>
			<td style="width:119px;"></td>
			<td>Section 4</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Typhoon FLA 9000 Laser Scanner</td>
			<td style="width:183px;">GE Heathcare Life Sciences</td>
			<td style="width:119px;">28-9558-08</td>
			<td>Section 3.5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ultrapure Distilled water</td>
			<td style="width:183px;">Invitrogen</td>
			<td style="width:119px;">10977-023</td>
			<td>Section 3.7.1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Mica disk</td>
			<td style="width:183px;">SPI Supplies</td>
			<td style="width:119px;">12001-26-2</td>
			<td>Section 4.1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Steel mounting disk</td>
			<td style="width:183px;">Ted Pella, Inc.</td>
			<td style="width:119px;">16218</td>
			<td>Section 4.1</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">carbon coated copper grid for TEM</td>
			<td style="width:183px;">Electron Microscopy Sciences</td>
			<td style="width:119px;">FCF400-Cu</td>
			<td>Section 7.2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">tweezers</td>
			<td style="width:183px;">Dumont</td>
			<td>0203-N5AC-PO</td>
			<td>Section 7.31</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">glow discharge system</td>
			<td style="width:183px;">Quorum Technologies</td>
			<td style="width:119px;">K100X</td>
			<td>Section 7.2</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">DNA Engine Tetrad 2 Peltier Thermal Cycler</td>
			<td style="width:183px;">BIO-RAD</td>
			<td>PTC&#8211;0240G</td>
			<td>Section 3.3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Owl Easycast B2 Mini Gel Electrophoresis Systems</td>
			<td style="width:183px;">ThermoScientific</td>
			<td>B2</td>
			<td>Section 3.4.3</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Seekam LE Agarose 500G</td>
			<td style="width:183px;">Lonza</td>
			<td style="width:119px;">50004</td>
			<td>Section 3.4.1</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">GeneRuler 1kb Plus DNA Ladder, Ready-To-Use 75-20000bp</td>
			<td style="width:183px;">ThermoScientific</td>
			<td style="width:119px;">SM1333</td>
			<td>Section 3.4.4</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Nanodrop 2000c UV-vis Spectrophotometer</td>
			<td style="width:183px;">ThermoScientific</td>
			<td style="width:119px;"></td>
			<td>Section 3.7</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">0.2 um filter</td>
			<td style="width:183px;">Corning Inc.</td>
			<td style="width:119px;">431219</td>
			<td>Section 7.1.2</td>
		</tr>
	</tbody>
</table>

self-assembly of complex two-dimensional shapes from single-stranded dna tiles

Current methods in DNA nano-architecture have successfully engineered a variety of 2D and 3D structures using principles of self-assembly. In this article, we describe detailed protocols on how to fabricate sophisticated 2D shapes through the self-assembly of uniquely addressable single-stranded DNA tiles which act as molecular pixels on a molecular canvas. Each single-stranded tile (SST) is a 42-nucleotide DNA strand composed of four concatenated modular domains which bind to four neighbors during self-assembly. The molecular canvas is a rectangle structure self-assembled from SSTs. A prescribed complex 2D shape is formed by selecting the constituent molecular pixels (SSTs) from a 310-pixel molecular canvas and then subjecting the corresponding strands to one-pot annealing. Due to the modular nature of the SST approach we demonstrate the scalability, versatility and robustness of this method. Compared with alternative methods, the SST method enables a wider selection of information polymers and sequences through the use of de novo designed and synthesized short DNA strands.

The self-assembly of SSTs (Figure 1) will yield a 24H &#215; 28T rectangle, as illustrated in Figure 2. DNA sequences for the different SSTs can be modified/optimized to enable streptavidin labeling (Figure 3 and 4), the transformation of a rectangle into a tube (Figure 5), the programmable self-assembly of SSTs to form tubes and rectangles of varying sizes (Figure 10), and the construction of 2D arbitrary shapes using t...

Watch this Scientific Journal Video about Self-assembly of Complex Two-dimensional Shapes from Single-stranded DNA Tiles at JoVE.com

Self-assembly of Complex Two-dimensional Shapes from Single-stranded DNA Tiles

DNA tiling is an effective approach to make programmable nanostructures. We describe the protocols to construct complex two-dimensional shapes by the self-assembly of single-stranded DNA tiles.

Current methods in DNA nano-architecture have successfully engineered a variety of 2D and 3D structures using principles of self-assembly. In this ...

self-assembly-complex-two-dimensional-shapes-from-single-stranded-dna

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Chemistry

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize.
In this paper, we detail visualized experimental protocols to create patterned particles, notably, (a) permanently bonded, hollow, polyhedra that self-assemble and self-seal due to the minimization of surface energy of liquefied hinges21-23 and (b) grippers that self-fold due to residual stress powered hinges24,25. The specific protocol described can be used to create particles with overall sizes ranging from the micrometer to the centimeter length scales. Further, arbitrary patterns can be defined on the surfaces of the particles of importance in colloidal science, electronics, optics and medicine. More generally, the concept of self-assembling mechanically rigid particles with self-sealing hinges is applicable, with some process modifications, to the creation of particles at even smaller, 100 nm length scales22, 26 and with a range of materials including metals21, semiconductors9 and polymers27. With respect to residual stress powered actuation of reconfigurable grasping devices, our specific protocol utilizes chromium hinges of relevance to devices with sizes ranging from 100 &mu;m to 2.5 mm. However, more generally, the concept of such tether-free residual stress powered actuation can be used with alternate high-stress materials such as heteroepitaxially deposited semiconductor films5,7 to possibly create even smaller nanoscale grasping devices.

We describe experimental details of the synthesis of patterned and reconfigurable particles from two dimensional (2D) precursors. This methodology can be used to create particles in a variety of shapes including polyhedra and grasping devices at length scales ranging from the micro to centimeter scale.

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two ...

Formation of Ordered Biomolecular Structures by the Self-assembly of Short Peptides

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control self-assembly and mimicking this process in vitro will bring about major advances in the areas of materials science and nanotechnology. Among the available biological building blocks, peptides have several advantages as they present substantial diversity, their synthesis in large scale is straightforward, and they can easily be modified with biological and chemical entities1,2. Several classes of designed peptides such as cyclic peptides, amphiphile peptides and peptide-conjugates self-assemble into ordered structures in solution. Homoaromatic dipeptides, are a class of short self-assembled peptides that contain all the molecular information needed to form ordered structures such as nanotubes, spheres and fibrils3-8. A large variety of these peptides is commercially available.
This paper presents a procedure that leads to the formation of ordered structures by the self-assembly of homoaromatic peptides. The protocol requires only commercial reagents and basic laboratory equipment. In addition, the paper describes some of the methods available for the characterization of peptide-based assemblies. These methods include electron and atomic force microscopy and Fourier-Transform Infrared Spectroscopy (FT-IR). Moreover, the manuscript demonstrates the blending of peptides (coassembly) and the formation of a &#34;beads on a string&#34;-like structure by this process.9 The protocols presented here can be adapted to other classes of peptides or biological building blocks and can potentially lead to the discovery of new peptide-based structures and to better control of their assembly.

This paper describes the formation of highly ordered peptide-based structures by the spontaneous process of self-assembly. The method utilizes commercially available peptides and common lab equipment. This technique can be applied to a large variety of peptides and may lead to the discovery of new peptide-based assemblies.

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control ...

Folding and Characterization of a Bio-responsive Robot from DNA Origami

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both stimuli and cargo can be tailored according to specific needs. Here we describe the DNA nanorobot fabrication protocol, with the use of the DNA origami technique. The procedure initiates by mixing short single-strand DNA staples into a stock mixture which is then added to a long, circular, single-strand DNA scaffold in presence of a folding buffer. A standard thermo cycler is programmed to gradually lower the mixing reaction temperature to facilitate the staples-to-scaffold annealing, which is the guiding force behind the folding of the nanorobot. Once the 60 hr folding reaction is complete, excess staples are discarded using a centrifugal filter, followed by visualization via agarose-gel electrophoresis (AGE). Finally, successful fabrication of the nanorobot is verified by transmission electron microscopy (TEM), with the use of uranyl-formate as negative stain.

DNA origami is a powerful method for fabricating precise nanoscale objects by programming the self-assembly of DNA molecules. Here we describe a protocol for the folding of a bio-responsive robot from DNA origami, its purification and negative staining for transmission electron microscopic imaging (TEM).

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully understood. We have traced the trajectories of individual nanoparticles using liquid-cell transmission electron microscopy (TEM) to investigate the mechanism of the assembly process. Herein, we present the protocols used for liquid-cell TEM studies of the self-assembly mechanism. First, we introduce the detailed synthetic protocols used to produce uniformly sized platinum and lead selenide nanoparticles. Next, we present the microfabrication processes used to produce liquid cells with silicon nitride or silicon windows and then describe the loading and imaging procedures of the liquid-cell TEM technique. Several notes are included to provide helpful tips for the entire process, including how to manage the fragile cell windows. The individual motions of nanoparticles tracked by liquid-cell TEM revealed that changes in the solvent boundaries caused by evaporation affected the self-assembly process of nanoparticles. The solvent boundaries drove nanoparticles to primarily form amorphous aggregates, followed by flattening of the aggregates to produce a 2-dimensional (2D) self-assembled structure. These behaviors are also observed for different nanoparticle types and different liquid-cell compositions.

Here we introduce experimental protocols for the real-time observation of a self-assembly process using liquid-cell transmission electron microscopy.

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully ...

Fabrication of Spherical and Worm-shaped Micellar Nanocrystals by Combining Electrospray, Self-assembly, and Solvent-based Structure Control

Micellar nanocrystals (micelles with encapsulated nanocrystals) have become an emerging major class of nanobiomaterials. We describe a method of fabricating micellar nanocrystals based on combining top-down electrospray, bottom-up self-assembly, and solvent-based structure control. This method involves first using electrospray to generate uniform ultrafine liquid droplets, each of which functions as a micro-reactor in which self-assembly reaction occurs forming micellar nanocrystals, with the structures (micelle shape and nanocrystal encapsulation) controlled by the organic solvent used. This method is largely continuous and produces high quality micellar nanocrystal products with an inexpensive structure control approach. By using a water-miscible organic solvent tetrahydrofuran (THF), worm-shaped micellar nanocrystals can be produced due to solvent-induced/facilitated micelle fusion. Compared with the common spherical micellar nanocrystals, worm-shaped micellar nanocrystals can offer minimized non-specific cellular uptake, thus enhancing biological targeting. By co-encapsulating multiple nanocrystals into each micelle, multifunctional or synergistic effects can be achieved. Current limitations of this fabrication method, which will be part of the future work, primarily include imperfect encapsulation in the micellar nanocrystal product and the incompletely continuous nature of the process.

The present work describes a method to fabricate micellar nanocrystals, an emerging major class of nanobiomaterials. This method combines top-down electrospray, bottom-up self-assembly, and solvent-based structure control. The fabrication method is largely continuous, can produce high quality products, and possesses an inexpensive means of structure control.

Micellar nanocrystals (micelles with encapsulated nanocrystals) have become an emerging major class of nanobiomaterials. We describe a method of ...

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. Here, we introduce the molten-salt synthesis (MSS) method for making metal oxide nanomaterials. Advantages over other methods include its simplicity, greenness, reliability, scalability, and generalizability. Using pyrochlore lanthanum hafnium oxide (La2Hf2O7) as a representative, we describe the MSS protocol for the successful synthesis of complex metal oxide nanoparticles (NPs). Furthermore, this method has the unique ability to produce NPs with different material features by changing various synthesis parameters such as pH, temperature, duration, and post-annealing. By fine-tuning these parameters, we are able to synthesize highly uniform, non-agglomerated, and highly crystalline NPs. As a specific example, we vary the particle size of the La2Hf2O7&#160;NPs by changing the concentration of the ammonium hydroxide solution used in the MSS process, which allows us to further explore the effect of particle size on various properties. It is expected that the MSS method will become a more popular synthesis method for nanomaterials and more widely employed in the nanoscience and nanotechnology community in the upcoming years.

Here, we demonstrate a unique, relatively low-temperature, molten-salt synthesis method for preparing uniform complex metal oxide lanthanum hafnate nanoparticles.

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. ...

Exfoliation and Analysis of Large-area, Air-Sensitive Two-Dimensional Materials

We describe methods for producing and analyzing large, thin flakes of air-sensitive two-dimensional materials. Thin flakes of layered or van der Waals crystals are produced using mechanical exfoliation, in which layers are peeled off a bulk crystal using adhesive tape. This method produces high-quality flakes, but they are often small and can be hard to find, particularly for materials with relatively high cleavage energies such as black phosphorus. By heating the substrate and the tape, two-dimensional material adhesion to the substrate is promoted, and the flake yield can be increased by up to a factor of ten. After exfoliation, it is necessary to image or otherwise analyze these flakes but some two-dimensional materials are sensitive to oxygen or water and will degrade when exposed air. We have designed and tested a hermetic transfer cell to temporarily maintain the inert environment of a glovebox so that air-sensitive flakes can be imaged and analyzed with minimal degradation. The compact design of the transfer cell is such that optical analysis of sensitive materials can be performed outside of a glovebox without specialized equipment or modifications to existing equipment.

A method for exfoliating large thin flakes of air sensitive two-dimensional materials and safely transporting them for analysis outside of a glovebox is presented.

We describe methods for producing and analyzing large, thin flakes of air-sensitive two-dimensional materials. Thin flakes of layered or van der Waals ...

Stable DNA Motifs, 1D and 2D Nanostructures Constructed from Small Circular DNA Molecules

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D DNA nanostructures. Over decades, the rapid development of DNA nanotechnology is attributed to the use of linear DNAs as the source materials. For example, the DAO (double crossover, antiparallel, odd half-turns) tile is well-known as a building block for construction of 2D DNA lattices; the core structure of DAO is made from two linear single-stranded (ss) oligonucleotides, like two ropes making a right hand granny&#160;knot. Herein, a new type of DNA tiles called cDAO (coupled DAO) are built using a small circular ss-DNA of c64nt or c84nt (circular 64 or 84 nucleotides) as the scaffold strand and several linear ss-DNAs as the staple strands. Perfect 1D and 2D nanostructures are assembled from cDAO tiles: infinite nanowires, nanospirals, nanotubes, nanoribbons; and finite nano-rectangles. Detailed protocols are described: 1) preparation by T4 ligase and purification by denaturing PAGE (polyacrylamide gel electrophoresis) of small circular oligonucleotides, 2) annealing of stable circular tiles, followed by native PAGE analysis, 3) assembling of infinite 1D nanowires, nanorings, nanospirals, infinite 2D lattices of nanotubes and nanoribbons, and finite 2D nano-rectangles, followed by AFM (Atomic Force Microscopy) imaging. The method is simple, robust, and affordable for most labs.

This article presents a detailed protocol for T4 ligation and denaturing PAGE purification of small circular DNA molecules, annealing and native PAGE analysis of circular tiles, assembling and AFM imaging of 1D and 2D DNA nanostructures, as well as agarose gel electrophoresis and centrifugation purification of finite DNA nanostructures.

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D ...