Yawei Sun

A pH‐Triggered, Fast‐Responding DNA Hydrogel

A fast, pH-responsive DNA hydrogel (see picture; right) was prepared by a three-armed DNA nanostructure (left) assembling together through the formation of intermolecular i-motif structures (middle). The hydrogel can be switched to the non-gel state in minutes by simply using environmental pH changes.

Self-assembled DNA hydrogels with designable thermal and enzymatic responsiveness.

or used as a programmable template to direct the assembly of nanoparticles. [ 14–17 ] Recently, the concept of DNA assembly has been expanded to construct “DNA hydrogels”, which are crosslinked networks swollen in an aqueous phase. [ 18–31 ] Though hydrogels have great potential in biological and medical applications, [ 32–36 ] such as drug and gene delivery, biosensing, and tissue engineering, studying the preparation of DNA hydrogels with designable properties is still in its early stages. In the past, several methods have been reported to prepare DNA hydrogels, for example, DNA directly extracted from the nucleus in nature, behaves like a long linear polymer and forms a hydrogel via physical entanglement or by chemical crosslinking of small molecules. [ 18 − 20] Similarly, DNA can be used as a negatively charged polymer and form a complex with cationic (poly)electrolytes through electrostatic interactions. [ 21 , 22 ] However, both methods treated DNA as a polymer and did not take advantage of the self-assembly of DNA into ordered structures, therefore, the resulting hydrogels lacked precise structural control and specifi c responses. Instead of using physical interactions, DNA can be covalently grafted onto synthetic polymers and serve as a cross-linker, the recognition of complementary DNA strands leads to crosslinking of polymer chains and causes hydrogel formation. [ 23 − 28] In general, the preparation of a DNA-polymer hybrid requires laborious modifi cation steps, and an easy and fast strategy to build tailored DNA hydrogels is desired. Luo and his coworkers have developed a new approach to construct

Highly efficient and enantioselective hydrogenation of quinolines and pyridines with Ir-Difluorphos catalyst

The combination of the readily available chiral bisphosphine ligand Difluorphos with [Ir(COD)Cl](2) in THF resulted in a highly efficient catalyst system for asymmetric hydrogenation of quinolines at quite low catalyst loadings (0.05-0.002 mol%), affording the corresponding products with high enantioselectivities (up to 96%), excellent catalytic activities (TOF up to 3510 h(-1)) and productivities (TON up to 43000). The same catalyst was also successfully applied to the asymmetric hydrogenation of trisubstituted pyridines with nearly quantitative yields and up to 98% ee. In these two reactions, the addition of I(2) additive is indispensable; but the amount of I(2) has a different effect on catalytic performance.

Frame‐Guided Assembly of Vesicles with Programmed Geometry and Dimensions

In molecular self-assembly molecules form organized structures or patterns. The control of the self-assembly process is an important and challenging topic. Inspired by the cytoskeletal-membrane protein lipid bilayer system that determines the shape of eukaryotic cells, we developed a frame-guided assembly process as a general strategy to prepare heterovesicles with programmed geometry and dimensions. This method offers greater control over self-assembly which may benefit the understanding of the formation mechanism as well as the functions of the cell membrane.

Amphiphilic DNA-dendron hybrid: a new building block for functional assemblies

A new kind of amphiphilic DNA-dendron hybrid consisting of a highly hydrophobic dendron and a single stranded DNA is synthesized. The hybrid could assemble into long nanofibers in aqueous phase. The hybridization property of DNA at the shell of fibers associated with the encapsulation ability of dendron at the inner core enable further functionalization, offering a unique class of supramolecular building block.

Highly efficient chemoselective construction of 2,2-dimethyl-6-substituted 4-piperidones via multi-component tandem Mannich reaction in ionic liquids

The room temperature ionic liquid [bmim][PF6] has been demonstrated to be an efficient and recyclable medium for highly chemoselective synthesis of 2,2-dimethyl-6-substituted 4-piperidones via a L-proline catalyzed tandem Mannich reaction of ammonia, aldehydes and acetone, and good yields were achieved for aryl and alkyl aldehydes.

Efficient one-pot production of 1,2-propanediol and ethylene glycol from microalgae (Chlorococcum sp.) in water

The catalytic valorization of microalgae, a sustainable feedstock to alleviate dependence on fossil fuel and offset greenhouse gases emissions, is of great significance for production of biofuels and value-added chemicals from aquatic plants. Here, an interesting catalytic process is reported to convert microalgae (Chlorococcum sp.) into 1,2-propanediol (1,2-PDO) and ethylene glycol (EG) in water over nickel-based catalysts. The influences of reaction temperature, initial H2 pressure and reaction time on the product distribution were systematically investigated by using a batch reactor. Under optimal reaction conditions (at 250 °C for 3 h with 6.0 MPa of H2 pressure), microalgae were directly and efficiently converted over a Ni–MgO–ZnO catalyst and the total yield of polyols was up to 41.5%. The excellent catalytic activity was attributed to the smaller size and better dispersion of Ni particles on the MgO–ZnO supporter based on the characterization results as well as its tolerance to nitrogen-containing compounds. Besides, the reaction pathway was proposed based on the formation of reaction intermediates and the results of model compound conversion.

A pH responsive dendron-DNA-protein hybrid supramolecular system

A pH responsive dendron-DNA-protein hybrid molecular system has been designed and prepared via chemical systhesis and assembly process. The size of this molecular system could be switched by the conformation change of the i-motif DNA. Its structure and switching mechanism has been characterized by mass spectroscopy, electrophoresis, circular dichroism (CD) spectroscopy and UV/Vis spectroscopy.

Preparation and Self‐folding of Amphiphilic DNA Origami

Amphiphilic DNA origami is prepared by dressing multiple hydrophobic molecules on a rectangular single layer DNA origami, which is then folded or coupled in sandwich-like structures with two outer DNA origami layer and one inner hydrophobic molecules layer. The preference to form different kinds of structures could be tailored by rational design of DNA origami.