Tunable Hydrophobicity in DNA Micelles:Design, Synthesis, and Characterization of a New Family of DNA Amphiphiles

This work describes the synthesis and characterization of a new family of DNA amphiphiles containing modified nucleobases. The hydrophobicity was imparted by the introduction of a dodec-1-yne chain at the 5-position of the uracil base, which allowed precise and simple tuning of the hydrophobic properties through solid-phase DNA synthesis. The micelles formed from these modified DNA sequences were characterized by atomic force microscopy, dynamic light scattering, and polyacrylamide gel electrophoresis. These experiments revealed the role of the quantity and location of the hydrophobic units in determining the morphology and stability of the micelles. The effects of hybridization on the physical characteristics of the DNA micelles were also studied; these results showed potential for the sequence-specific noncovalent functionalization of the self-assembled aggregates

The abundances of hydrocarbon functional groups in the interstellar medium inferred from laboratory spectra of hydrogenated and methylated polycyclic aromatic hydrocarbons

Infrared (IR) absorption spectra of individual polycyclic aromatic hydrocarbons (PAHs) containing methyl (-CH3), methylene (>CH2), or diamond-like *CH groups and IR spectra of mixtures of methylated and hydrogenated PAHs prepared by gas phase condensation were measured at room temperature (as grains in pellets) and at low temperature (isolated in Ne matrices). In addition, the PAH blends were subjected to an in-depth molecular structure analysis by means of high-performance liquid chromatography, nuclear magnetic resonance spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Supported by calculations at the density functional theory level, the laboratory results were applied to analyze in detail the aliphatic absorption complex of the diffuse interstellar medium at 3.4 mu-m and to determine the abundances of hydrocarbon functional groups. Assuming that the PAHs are mainly locked in grains, aliphatic CHx groups (x = 1,2,3) would contribute approximately in equal quantities to the 3.4 mu-m feature (N_{CHx} / N_{H} approx 10^{-5} - 2 * 10^{-5}). The abundances, however, may be two to four times lower if a major contribution to the 3.4 mu-m feature comes from molecules in the gas phase. Aromatic =CH groups seem to be almost absent from some lines of sight, but can be nearly as abundant as each of the aliphatic components in other directions (N_{=CH} / N_{H} < 2 * 10^{-5}; upper value for grains). Due to comparatively low binding energies, astronomical IR emission sources do not display such heavy excess hydrogenation. At best, especially in proto-planetary nebulae, >CH2 groups bound to aromatic molecules, i.e., excess hydrogens on the molecular periphery only, can survive the presence of a nearby star.Comment: 34 pages, 19 figures, ApJS, 208, 2

Electronic Band Dispersion of Graphene Nanoribbons via Fourier-Transformed Scanning Tunneling Spectroscopy

Atomically precise armchair graphene nanoribbons of width $N=7$ (7-AGNRs) are investigated by scanning tunneling spectroscopy (STS) on Au(111). The analysis of energy-dependent standing wave patterns of finite length ribbons allows, by Fourier transformation, the direct extraction of the dispersion relation of frontier electronic states. Aided by density functional theory calculations, we assign the states to the valence band, the conduction band and the next empty band of 7-AGNRs, determine effective masses of $0.42\pm 0.08\,m_e$, $0.40\pm 0.18\,m_e$ and $0.20\pm 0.03\,m_e$, respectively, and a band gap of $2.37\pm 0.06$ eV.Comment: 20 pages, 7 figure

Synthesis and Optical Properties of Water-Soluble NIR Absorbing Star Polypeptides based on Functional Rylene Dyes

Summary : In this contribution, the synthesis of two novel amino-functionalized terrylene and quaterrylene diimide derivatives is described. These chromophores have been used as initiators for the ring-opening polymerization of Nɛ-benzyloxycarbonyl-L-lysine N-carboxyanhydride. 4-Arm star polypeptides were obtained with number average chain lengths of 50 and 100 units. Removal of the Nɛ-benzyloxycarbonyl side-chain protective groups afforded unprecedented water-soluble terrylene and quaterrylene based star polypeptides that combined high extinction coefficients in the NIR range with very good chemical and photostabilit

Amino-substituted rylene dicarboximides and their quinoidal charge delocalization after deprotonation

A novel approach towards NIR absorption, including the deprotonation and subsequent quinoidal charge delocalization of amino-substituted rylene dicarboximides, is presented