Computational de novo design and characterization of a protein that selectively binds a highly hyperpolarizable abiological chromophore.

This work reports the first example of a single-chain protein computationally designed to contain four α-helical segments and fold to form a four-helix bundle encapsulating a supramolecular abiological chromophore that possesses exceptional nonlinear optical properties. The 109-residue protein, designated SCRPZ-1, binds and disperses an insoluble hyperpolarizable chromophore, ruthenium(II) [5-(4'-ethynyl-(2,2';6',2″-terpyridinyl))-10,20-bis(phenyl)porphinato]zinc(II)-(2,2';6',2″-terpyridine)(2+) (RuPZn) in aqueous buffer solution at a 1:1 stoichiometry. A 1:1 binding stoichiometry of the holoprotein is supported by electronic absorption and circular dichroism spectra, as well as equilibrium analytical ultracentrifugation and size exclusion chromatography.

Light induced nanowire assembly: the electrostatic alignment of semiconductor nanowires into functional macroscopic yarns.

The electrostatic alignment and directed assembly of semiconductor nanowires into macroscopic, centimeter-long yarns is demonstrated. Different morphologies can be produced, including longitudinally segmented/graded yarns or mixed composition fibers. Nanowire yarns display long range photoconductivities and open up exciting opportunities for potential use in future nanowire-based textiles or in solar photovoltaics.

Single cell responses to spatially controlled photosensitized production of extracellular singlet oxygen.

The response of individual HeLa cells to extracellularly produced singlet oxygen was examined. The spatial domain of singlet oxygen production was controlled using the combination of a membrane-impermeable Pd porphyrin-dendrimer, which served as a photosensitizer, and a focused laser, which served to localize the sensitized production of singlet oxygen. Cells in close proximity to the domain of singlet oxygen production showed morphological changes commonly associated with necrotic cell death.

The roles of molecular structure and effective optical symmetry in evolving dipolar chromophoric building blocks to potent octopolar nonlinear optical chromophores.

A series of mono-, bis-, tris-, and tetrakis(porphinato)zinc(II) (PZn)-elaborated ruthenium(II) bis(terpyridine) (Ru) complexes have been synthesized in which an ethyne unit connects the macrocycle meso carbon atom to terpyridyl (tpy) 4-, 4'-, and 4''-positions. These supermolecular chromophores, based on the ruthenium(II) [5-(4'-ethynyl-(2,2';6',2''-terpyridinyl))-10,20-bis(2',6'-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2,2';6',2''-terpyridine)(2+) bis-hexafluorophosphate (RuPZn) archetype, evince strong mixing of the PZn-based oscillator strength with ruthenium terpyridyl charge resonance bands. Potentiometric and linear absorption spectroscopic data indicate that for structures in which multiple PZn moieties are linked via ethynes to a [Ru(tpy)(2)](2+) core, little electronic coupling is manifest between PZn units, regardless of whether they are located on the same or opposite tpy ligand.

Phase transfer catalysts drive diverse organic solvent solubility of single-walled carbon nanotubes helically wrapped by ionic, semiconducting polymers.

Use of phase transfer catalysts such as 18-crown-6 enables ionic, linear conjugated poly[2,6-{1,5-bis(3-propoxysulfonicacidsodiumsalt)}naphthylene]ethynylene (PNES) to efficiently disperse single-walled carbon nanotubes (SWNTs) in multiple organic solvents under standard ultrasonication methods. Steady-state electronic absorption spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM) reveal that these SWNT suspensions are composed almost exclusively of individualized tubes. High-resolution TEM and AFM data show that the interaction of PNES with SWNTs in both protic and aprotic organic solvents provides a self-assembled superstructure in which a PNES monolayer helically wraps the nanotube surface with periodic and constant morphology (observed helical pitch length = 10 ± 2 nm); time-dependent examination of these suspensions indicates that these structures persist in solution over periods that span at least several months.