A promiscuous aminoacyl-tRNA synthetase that incorporates cysteine, methionine, and alanine homologs into proteins.

A mutant Escherichia coli leucyl-tRNA synthetase has been evolved for the selective incorporation of the methionine homolog 1 into proteins in yeast. This single aminoacyl-tRNA synthetase is capable of charging an amber suppressor EctRNA(CUA)(Leu) with at least eight different amino acids including methionine and cysteine homologs, as well as straight chain aliphatic amino acids. In addition we show that incorporation yields for these amino acids can be increased substantially by mutations in the editing CP1 domain of the E. coli leucyl-tRNA synthetase.

Using hydrogen bonds to direct the assembly of crowded aromatics.

This Minireview details the design, synthesis, and self-assembly of a new class of crowded aromatics that form columnar superstructures. The assembly of these subunits produces helical and polar stacks, whose assembly can be directed with electric fields. In concentrated solutions, these self-assembled helical rods exhibit superhelical arrangements that reflect circularly polarized light at visible wavelengths. Depending on the side chains employed, spin-cast films yield either polar monolayers or isolated strands of molecules that can be visualized with scanning probe microscopy. Also detailed herein are methods to link these mesogens together to produce monodisperse oligomers that fold into defined secondary conformations.

Molecular interactions in one-dimensional organic nanostructures.

Intermolecular interactions involving pi-pi interaction and hydrogen bonding are used to create one-dimensional molecular nanostructures of hexasubstituted aromatics. Site-selective steady state fluorescence, time-resolved fluorescence, scanning electron microscopy, and atomic force microscopy measurements detail the intermolecular interactions that drive the aromatic molecules to self-assemble in solution to form well-ordered columnar stacks. These nanostructures, formed in solution, vary in their number, size, and structure depending on the solvent used. In addition, our results indicate that the substituents/ side groups and the proper choice of the solvent can be used to tune the intermolecular interactions. The 1D stacks and their aggregates can be easily transferred by solution casting, thus allowing a simple preparation of molecular nanostructures on different surfaces.

Synthesis, self-assembly, and switching of one-dimensional nanostructures from new crowded aromatics.

This study outlines a versatile and expeditious synthesis of the first derivatives of a new class of benzene that is substituted with both three amide and three alkyne substituents. Sparsely covered monolayer films, made through spin-casting, reveal one-dimensional nanostructures that can be visualized with atomic force microscopy. In bulk, synchrotron X-ray diffraction and polarized light microscopy show that these nanostructured columns assemble further into a two-dimensional liquid crystalline phase. The birefringence of this phase can be switched by application of an electric field. The half-time for the liquid crystalline phase to switch is very fast and proportional to the applied voltage.

Tuning intermolecular attraction to create polar order and one-dimensional nanostructures on surfaces.

This study utilizes atomic force microscopy and electrostatic force microscopy to investigate the orientation of overcrowded aromatics in films with submonolayer coverage. The results demonstrate that the side chains in the molecules can be used as a tool to control the molecular order and orientation in thin films. For molecules that do not self-associate well, the interaction with the substrate dominates, and the molecules orient with their aromatic planes parallel to the surface. These monolayers have measurable polar order. For molecules that self-associate well, the opposite orientation is observed. These films are comprised of isolated stacks of molecules parallel to the surface.