Reprogramming the assembly of unmodified DNA with a small molecule

The ability of DNA to store and encode information arises from base pairing of the four-letter nucleobase code to form a double helix. Expanding this DNA ‘alphabet’ by synthetic incorporation of new bases can introduce new functionalities and enable the formation of novel nucleic acid structures. However, reprogramming the self-assembly of existing nucleobases presents an alternative route to expand the structural space and functionality of nucleic acids. Here we report the discovery that a small molecule, cyanuric acid, with three thymine-like faces reprogrammes the assembly of unmodified poly(adenine) (poly(A)) into stable, long and abundant fibres with a unique internal structure. Poly(A) DNA, RNA and peptide nucleic acid all form these assemblies. Our studies are consistent with the association of adenine and cyanuric acid units into a hexameric rosette, which brings together poly(A) triplexes with a subsequent cooperative polymerization. Fundamentally, this study shows that small hydrogen-bonding molecules can be used to induce the assembly of nucleic acids in water, which leads to new structures from inexpensive and readily available materials

Reticular synthesis of porous molecular 1D nanotubes and 3D networks

Synthetic control over pore size and pore connectivity is the crowning achievement for porous metal–organic frameworks (MOFs). The same level of control has not been achieved for molecular crystals, which are not defined by strong, directional intermolecular coordination bonds. Hence, molecular crystallization is inherently less controllable than framework crystallization, and there are fewer examples of ‘reticular synthesis’, in which multiple building blocks can be assembled according to a common assembly motif. Here we apply a chiral recognition strategy to a new family of tubular covalent cages to create both 1D porous nanotubes and 3D diamondoid pillared porous networks. The diamondoid networks are analogous to MOFs prepared from tetrahedral metal nodes and linear ditopic organic linkers. The crystal structures can be rationalized by computational lattice-energy searches, which provide an in silico screening method to evaluate candidate molecular building blocks. These results are a blueprint for applying the ‘node and strut’ principles of reticular synthesis to molecular crystals

An Organic-solid With Wide Channels Based On Hydrogen-bonding Between Macrocycles

RESEARCH on microporous solids has focused largely on inorganic materials such as aluminosilicates (zeolites), aluminophosphates, pillared clays and other layered materials(1,2). An elusive goal has been the design of new materials with specific properties such as selective adsorption and catalytic activity. It would be very useful if the tools of molecular synthesis could be brought to bear on this problem. Here we report the design, based on a modular approach, and the crystal structure of an organic solid with large-diameter (about 9 Angstrom) extended channels. The channels are formed from planar, rigid macrocyclic building blocks. Onto the outer rim of the macrocycles are attached phenolic groups, which form hexagonally closest-packed two-dimensional hydrogen-bonded networks. Extended channels result from the stacking of these layers in a way that maintains registry between the macrocyclic cavities, and these channels are filled with solvent molecules. This approach potentially offers a simple means to exercise control over pore size and shape in the solid state.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62826/1/371591a0.pd