Tunable disassembly of micelles using a redox trigger

A simple design for stimuli-responsive micellar disassembly has been demonstrated on the basis of a surfactant molecule wherein the hydrophilic head group is connected to the hydrophobic tail through a redox-sensitive disulfide linker. The disassembly kinetics is tuned by mixing the stimuli-responsive surfactant with a suitable nonresponsive co-surfactant in various ratios, which helps in gaining control over the release rate of encapsulated dye molecules from such mixed micelles.     

Ultra-resolution imaging of a self-assembling biomolecular system using robust carbon nanotube AFM probes

Nanoscale structural features of a novel self-assembling DNA based nanostructure have been resolved. Image data is of sufficient resolution to allow molecular orientation and the effect of surface adsorption to be characterized. This has been achieved using AFM with probes employing carbon nanotubes attached via a thin film of plasma polymerized hexane. This presents the nanotube with a highly hydrophobic coating to which it can adsorb, increasing production success and probe robustness.     

On the relationship between quantum control landscape structure and optimization complexity

It has been widely observed in optimal control simulations and experiments that state preparation is surprisingly easy to achieve, regardless of the dimension N of the system Hilbert space. In contrast, simulations for the generation of targeted unitary transformations indicate that the effort increases exponentially with N. In order to understand such behavior, the concept of quantum control landscapes was recently introduced, where the landscape is defined as the physical objective, as a function of the control variables. The present work explores how the local structure of the control landscape influences the effectiveness and efficiency of quantum optimal control search efforts. Optimizations of state and unitary transformation preparation using kinematic control variables (i.e., the elements of the action matrix) are performed with gradient, genetic, and simplex algorithms. The results indicate that the search effort scales weakly, or possibly independently, with N for state preparation, while the search effort for the unitary transformation objective increases exponentially with N. Analysis of the mean path length traversed during a search trajectory through the space of action matrices and the local structure along this trajectory provides a basis to explain the difference in the scaling of the search effort with N for these control objectives. Much more favorable scaling for unitary transformation preparation arises upon specifying an initial action matrix based on state preparation results. The consequences of choosing a reduced number of control variables for state preparation is also investigated, showing a significant reduction in performance for using fewer than 2N-2 variables, which is consistent with the topological analysis of the associated landscape.     

Synthesis and characterization of 2,7-bis(pentafluorophenylethynyl)hexafluoroheterofluorenes: new materials with high electron affinities

The synthesis, optical, electrochemical and physical characterization of 2,7-bis(pentafluorophenylethynyl)hexafluoroheterofluorenes is described along with a preliminary evaluation of their performance in photovoltaic applications.     

A [3 + 3] annelation approach to (+)-rhopaloic acid B

A general and enantiospecific [3 + 3] reaction toward functionalized pyrans is reported that has been employed in the first enantioselective synthesis of (+)-rhopaloic acid B.     

31P NMR investigation of backbone dynamics in DNA binding sites

The backbone conformation of DNA plays an important role in the indirect readout mechanisms for protein--DNA recognition events. Thus, investigating the backbone dynamics of each step in DNA binding sequences provides useful information necessary for the characterization of these interactions. Here, we use 31P dynamic NMR to characterize the backbone conformation and dynamics in the Dickerson dodecamer, a sequence containing the EcoRI binding site, and confirm solid-state 2H NMR results showing that the C3pG4 and C9pG10 steps experience unique dynamics and that these dynamics are quenched upon cytosine methylation. In addition, we show that cytosine methylation affects the conformation and dynamics of neighboring nucleotide steps, but this effect is localized to only near neighbors and base-pairing partners. Last, we have been able to characterize the percent BII in each backbone step and illustrate that the C3pG4 and C9pG10 favor the noncanonical BII conformation, even at low temperatures. Our results demonstrate that 31P dynamic NMR provides a robust and efficient method for characterizing the backbone dynamics in DNA. This allows simple, rapid determination of sequence-dependent dynamical information, providing a useful method for studying trends in protein-DNA recognition events.     

Ab initio investigation of titanium hydroxide isomers and their cations, TiOH(0,+) and HTiO(0,+)

We studied the electronic and geometrical structure of the [Ti, O, H](0,+) species, using large basis sets and both single-reference coupled cluster and multireference configuration interaction methodologies. The electronic structure of HTiO(0,+) is interpreted qualitatively in terms of a hydrogen atom bonding to TiO(0,+), while the structure of TiOH(0,+) is interpreted in terms of Ti(+,2+) bonding to OH(-). Potential energy profiles are reported as functions of the Ti-OH and H-TiO bond lengths, and of the H-Ti-O angle. For a total of 33 stationary points on the potential energy surfaces, we report absolute energies, geometries, and harmonic frequencies. For the neutral species, dipole moments are also given.     

Infrared absorption by collisional H2-He complexes at temperatures up to 9000 K and frequencies from 0 to 20,000 cm(-1)

Quantum chemical methods have been used elsewhere to obtain the potential energy surface (PES) and the induced dipole surface (IDS) of H(2)-He collisional complexes at eight different H-H bond distances, fifteen atom-molecule separations, and 19 angular orientations each [X. Li, A. Mandal, E. Miliordos, and K. L. C. Hunt, J. Chem. Phys. 136, 044320 (2012)]. An atom-molecule state-to-state scattering formalism is employed, which couples the collisional molecular complex to the electromagnetic radiation field. In this way, we obtain theoretical collision-induced absorption (CIA) spectra of H(2)-He complexes for frequencies from 0 to 20,000 cm(-1) and temperatures up to 9000 K. The work is based on the fundamental theory and is motivated by current research of certain astronomical objects, such as cool white dwarf stars, cool main sequence stars, M dwarfs, exoplanets, so-called "first" stars. We compare our theoretical results to existing laboratory measurements of CIA spectra; very close agreement of theory and measurement is observed. We also discuss similar previous theoretical efforts.     

Self‐assembled hydrogen‐bonded bilayers in 1,4‐diazabicyclo[2.2.2]octane–N‐(phosphonomethyl)iminodiacetic acid–water (1/1/1.5)

The title compound is a hydrated salt, 1,4‐diazo­nia­bi­cyclo­[2.2.2]­octane–N‐[(hydroxy­phosphinato)­methyl]­iminiodi­acetate–water (1/1/1.5), C₆H₁₄N₂²⁺·C₅H₈NO₇P^2?·1.5H₂O, in which one of the water mol­ecules lies across a twofold rotation axis in space group P2/n. The ionic components are linked into sheets by a combination of a three‐centre N—H?(O)₂ hydrogen bond and two‐centre O—H?O and N—H?O hydrogen bonds, and these sheets are pairwise linked by the water mol­ecules into bilayers, by means of further O—H?O hydrogen bonds.