Assembly of T-Shaped Amphiphilic Thiazoles on the Air-Water Interface: Impact of Polar Chromophore Moieties, as Well as Dipolarity and π-Extension of the Chromophore on the Supramolecular Structure.

The supramolecular structure essentially determines the properties of organic thin films. In this work, we systematically investigate the influence of the chromophore on the supramolecular structure formation at air-water interfaces by means of the Langmuir-Blodgett technique. Therefore, we focus on the recently introduced class of double-anchor T-shaped amphiphilic dyes, namely, 4-hydroxy-thiazole chromophores that are centrally equipped with an amphiphilicity-inducing hexanoic acid. The thiazoles contain hydrophilic subphase-anchor groups in the 2-position (4- N, N-dimethylaminophenyl (Am), 2-pyridyl (Py), and 4-nitrophenyl (Ni)), whereas the chromophores are systematically extended in the 5-position with various substituents. The combination of the Langmuir technique with online fluorescence measurements revealed that the π-π interactions that are pronounced in the case of 4-methoxybiphenyl derivatives yield the most distinct supramolecular structures. Whereas in the case of Py and Ni derivatives ordered J-type supramolecular structures in microdomains are formed, the Am derivative forms ordered supramolecular structures that are more homogeneous, which are, however, not stabilized by J-type dipolar interactions. Because of the synergetic π-π and dipolar stabilizations, the Ni derivative bearing the 4-methoxybiphenyl unit forms exceptionally stable quasi-two-dimensional Langmuir monolayers reaching very high surface pressures beyond 60 mN/m without any sign of disturbance of the Langmuir monolayer.

Ab Initio Prediction of Fluorescence Lifetimes Involving Solvent Environments by Means of COSMO and Vibrational Broadening.

The fluorescence lifetime is a key property of fluorophores that can be utilized for microenvironment probing, analyte sensing, and multiplexing as well as barcoding applications. For the rational design of lifetime probes and barcodes, theoretical methods have been developed to enable the ab initio prediction of this parameter, which depends strongly on interactions with solvent molecules and other chemical species in the emitters immediate environment. In this work, we investigate how a conductor-like screening model (COSMO) can account for variations in fluorescence lifetimes that are caused by such fluorophore-solvent interactions. Therefore, we calculate vibrationally broadened fluorescence spectra using the nuclear ensemble method to obtain distorted molecular geometries to sample the electronic transitions with time-dependent density functional theory (TDDFT). The influence of the solvent on fluorescence lifetimes is accounted for with COSMO. For example, for 4-hydroxythiazole fluorophore containing different heteroatoms and acidic and basic moieties in aprotic and protic solvents of varying polarity, this approach was compared to experimentally determined lifetimes in the same solvents. Our results demonstrate a good correlation between theoretically predicted and experimentally measured fluorescence lifetimes except for the polar solvents ethanol and acetonitrile that can specifically interact with the heteroatoms and the carboxylic acid of the thiazole derivative.

Absorption and Fluorescence Features of an Amphiphilic meso-Pyrimidinylcorrole: Experimental Study and Quantum Chemical Calculations.

Corroles are emerging as an important class of macrocycles with numerous applications because of their peculiar photophysical and metal chelating properties. meso-Pyrimidinylcorroles are easily deprotonated in certain solvents, which changes their absorption and emission spectra as well as their accessible supramolecular structures. To enable control over the formation of supramolecular structures, the dominant corrole species, i.e., the deprotonated form or one of the two NH-tautomers, needs to be identified. Therefore, we focus in the present article on the determination of the UV-vis spectroscopic properties of the free-base NH-tautomers and the deprotonated form of a new amphiphilic meso-pyrimidinylcorrole that can assemble to supramolecular structures at heterointerfaces as utilized in the Langmuir-Blodgett and liquid-liquid interface precipitation techniques. After quantification of the polarities of the free-base NH-tautomers and the deprotonated form by means of quantum chemically derived electrostatic potential distributions at the corroles' van der Waals surfaces, the preferential stabilization of (some of) the considered species in solvents of different polarity is identified by means of absorption spectroscopy. For the solutions with complex mixtures of species, we applied fluorescence excitation spectroscopy to estimate the relative weights of the individual corrole species. This technique might also be applied to identify dominating species in molecularly thin films directly on the subphase' surface of Langmuir-Blodgett troughs. Supported by quantum chemical calculations we were able to differentiate between the spectral signatures of the individual NH-tautomers by means of fluorescence excitation spectroscopy.

Efficient implementation of effective core potential integrals and gradients on graphical processing units.

Effective core potential integral and gradient evaluations are accelerated via implementation on graphical processing units (GPUs). Two simple formulas are proposed to estimate the upper bounds of the integrals, and these are used for screening. A sorting strategy is designed to balance the workload between GPU threads properly. Significant improvements in performance and reduced scaling with system size are observed when combining the screening and sorting methods, and the calculations are highly efficient for systems containing up to 10 000 basis functions. The GPU implementation preserves the precision of the calculation; the ground state Hartree-Fock energy achieves good accuracy for CdSe and ZnTe nanocrystals, and energy is well conserved in ab initio molecular dynamics simulations.

How Does Peripheral Functionalization of Ruthenium(II)-Terpyridine Complexes Affect Spatial Charge Redistribution after Photoexcitation at the Franck-Condon Point?

Ruthenium polypyridine-type complexes are extensively used sensitizers to convert solar energy into chemical and/or electrical energy, and they can be tailored through their metal-to-ligand charge-transfer (MLCT) properties. Much work has been directed at harnessing the triplet MLCT state in photoinduced processes, from sophisticated molecular architectures to dye-sensitized solar cells. In dye-sensitized solar cells, strong coupling to the semiconductor exploits the high reactivity of the (hot) singlet/triplet MLCT state. In this work, we explore the nature of the (1) MLCT states of remotely substituted Ru(II) model complexes by both experimental and theoretical techniques. Two model complexes with electron-withdrawing (i.e. NO2 ) and electron-donating (i.e. NH2 ) groups were synthesized; these complexes contained a phenylene spacer to serve as a spectroscopic handle and to confirm the contribution of the remote substituent to the (1) MLCT transition. [Ru(tpy)2 ](2+) -based complexes (tpy=2,2':6',2''-terpyridine) were further desymmetrized by tert-butyl groups to yield unidirectional (1) MLCTs with large transition dipole moments, which are beneficial for related directional charge-transfer processes. Detailed comparison of experimental spectra (deconvoluted UV/Vis and resonance Raman spectroscopy data) with theoretical calculations based on density functional theory (including vibronic broadening) revealed different properties of the optically active bright (1) MLCT states already at the Franck-Condon point.

Test performance characteristics of Anti-HEV IgG assays strongly influence hepatitis E seroprevalence estimates.

Hepatitis E virus (HEV) seroprevalences of 0.3%-53% were reported from industrialized countries. Because these estimates may be influenced by detection assays, this study compares 3 frequently used tests for HEV detection: the MP Diagnostics HEV immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA), the Axiom Diagnostics HEV IgG enzyme immunoassay (EIA), and the Mikrogen recomLine HEV IgG assay. Sera from 200 healthy healthcare workers and 30 individuals with acute HEV infection were analyzed. Among the healthy individuals, HEV IgG was found in 4.5% by the MP Diagnostics assay, in 29.5% by the Axiom Diagnostics assay, and in 18% by the Mikrogen assay. Among individuals with acute HEV infection, positive results were obtained for 83.3%, 100%, and 96.7%, respectively. Thus, the 3 assays show clear differences in diagnostic sensitivity.

Theoretical reconstruction and elementwise analysis of photoelectron spectra for imidazolium-based ionic liquids.

We have recently measured core level and valence band XPS, UPS, and MIES spectra of two room temperature ionic liquids composed of bis(trifluoromethylsulfonyl)imide anions ([Tf(2)N](-)) and either 1-ethyl-3-methyl-imidazolium ([EMIm](+)) or 1-octyl-3-methyl-imidazolium cations ([OMIm](+)). [T. Ikari, A. Keppler, M. Reinmöller, W. J. D. Beenken, S. Krischok, M. Marschewski, W. Maus-Friedrichs, O. Höfft and F. Endres, e-J. Surf. Sci. Nanotechnol., 2010, 8, 241.] In the present work we analyze these spectra by means of partial density of states (pDOS) as calculated from a single ion pair of the respective ionic liquid using density functional theory (DFT). Subsequently we reconstruct the XPS and UPS spectra by considering photoemission cross sections and analyze the MIES spectra by pDOS, which provides us decisive hints to the ionic liquid surface structure.

Detection of hepatitis E virus (HEV) from porcine livers in Southeastern Germany and high sequence homology to human HEV isolates.

BACKGROUND: Hepatitis E virus (HEV) has been identified as an emerging cause of infectious hepatitis over the last years in developed countries. In contrast to travel associated hepatitis E, zoonotic sources of infection are suspected for autochthonous cases in Europe. OBJECTIVE: Since pigs are known reservoirs of HEV, we tested porcine livers sold as food in Southeastern Germany for the presence of hepatitis E virus RNA. STUDY DESIGN: We purchased 200 porcine liver samples in 81 butcher shops and grocery stores in Regensburg, Germany. Nucleic acid preparations were tested for the presence of HEV RNA by quantitative real-time PCR (RT-qPCR). HEV isolates from positive samples were characterized by partial sequencing of ORF1 and ORF2 regions in the HEV genome and by phylogenetic analysis. RESULTS: Specimens from eight (4%) of 200 purchased pig livers had detectable HEV RNA amounts. Sequence determination and phylogenetic analysis allowed two novel isolates to be classified as HEV genotype 3, subgenotype 3a (swR437) and 3c (swR269), respectively. Both novel swine HEV isolates showed high sequence homology to isolates obtained from patients with acute HEV infection from the same geographic region. CONCLUSIONS: These results support the suggested role of undercooked pig products in food as a source of zoonotic HEV infection for humans. It remains to be clarified if this mechanism of transmission is responsible for the surprisingly high anti-HEV IgG prevalence recently observed in some European countries and the USA.