“Printing” DNA Strand Patterns on Small Molecules with Control of Valency,Directionality, and Sequence

The incorporation of synthetic molecules as corner units in DNA structures has been of interest over the last two decades. In this work, we present a facile method for generating branched small molecule‐DNA hybrids with controllable valency, different sequences, and directionalities (5′–3′) using a “printing” process from a simple 3‐way junction structure. We also show that the DNA‐imprinted small molecule can be extended asymmetrically using polymerase chain reaction (PCR) and can be replicated chemically. This strategy provides opportunities to achieve new structural motifs in DNA nanotechnology and introduce new functionalities to DNA nanostructures.     

Creation of “Rose Petal” and “Lotus Leaf” Effects on Alumina by Surface Functionalization and Metal‐Ion Coordination

Functional differences between superhydrophobic surfaces, such as lotus leaf and rose petals, are due to the subtle architectural features created by nature. Mimicry of these surfaces with synthetic molecules continues to be fascinating as well as challenging. Herein, we demonstrate how inherently hydrophilic alumina surface can be modified to give two distinct superhydrophobic behaviors. Functionalization of alumina with an organic ligand resulted in a rose‐petal‐like surface (water pinning) with a contact angle of 145° and a high contact angle hysteresis (±69°). Subsequent interaction of the ligand with Zn²⁺ resulted in a lotus‐leaf‐like surface with water rolling behavior owing to high contact angle (165°) and low‐contact‐angle‐hysteresis (±2°). In both cases, coating of an aromatic bis‐aldehyde with alkoxy chain substituents was necessary to emulate the nanowaxy cuticular feature of natural superhydrophobic materials.     

“On‐Droplet” Chemistry: The Cycloaddition of Diethyl Azodicarboxylate and Quadricyclane

Sharpless and co‐workers previously studied the [2σ+2σ+2π] cycloaddition of diethyl azodicarboxylate (DEAD) and quadricyclane and reported that the addition of water to the neat reagents caused an acceleration in the reaction rate, giving birth to what has been called “on‐water” chemistry. We have examined the same reaction in aqueous microdroplets (ca. 5 μm diameter) and find that the cycloaddition reaction is accelerated even further (by a factor of 10²) compared to that of the “on‐water” reaction reported previously. The trends of acceleration in solvents other than water demonstrated by Sharpless and colleagues were replicated in the corresponding microdroplet experiments. We also find that DEAD reacts with itself to form a variety of hydrazine carboxylates and intercept intermediates of this reaction in microdroplets to validate a mechanism proposed herein. We suggest that “on‐droplet” chemistry, similar to “on‐water” chemistry, may be a general process of synthetic interest.     

“Photoclick” Postsynthetic Modification of DNA

A new DNA building block bearing a push–pull‐substituted diaryltetrazole linked to the 5‐position of 2′‐deoxyuridine through an aminopropynyl group was synthesized. The accordingly modified oligonucleotide allows postsynthetic labeling with a maleimide‐modified sulfo‐Cy3 dye, N‐methylmaleimide, and methylmethacrylate as dipolarophiles by irradiation at 365 nm (LED). The determined rate constant of (23±7) M ^?1 s^?1 is remarkably high with respect to other copper‐free bioorthogonal reactions and comparable with the copper‐catalyzed cycloaddition between azides and acetylenes.