Solid-phase synthesis, bioconjugation, and toxicology of novel cationic oligopeptoids for cellular drug delivery.

For many therapeutic applications, it has become more and more important to find synthetic compounds that have the ability to transport a variety of drugs and cargo molecules into cells and tissues. Like arginine-rich cell-penetrating peptides (CPPs), it is already known that peptide mimetics such as beta-peptides and peptoids can also express a transport function. In this study, ten fluorophore-labeled chiral and achiral peptoids with different backbone lengths and side chains as well as three peptoids coupled to a therapeutically active porphyrin moiety were prepared using a highly modular solid-phase synthesis (SPP) approach.

Stereoelectronic effects in cyclic sulfoxides, sulfones, and sulfilimines: application of the Perlin effect to conformational analysis.

The 1JC--H coupling constants in conformationally constrained sulfoxides, bissulfoxides, sulfoxide-sulfones, and sulfilimines derived from 2-benzylidene-1,3-dithiane and 2-(2,2-dimethylpropylidene)-1,3-dithiolane were measured by means of HMQC and HSQC NMR experiments and the Perlin effects were calculated. The type and the relative configuration of S==X groups (X= O, NTos) in these compounds have a strong influence on the magnitude of coupling constants for axial and equatorial C--H bonds, respectively. Axial S==O bonds give rise to a stereoelectronic effect on antiperiplanar axial C--H bonds.

Predicting the QRS complex and detecting small changes using principal component analysis.

In this paper, a new method for QRS complex analysis and estimation based on principal component analysis (PCA) and polynomial fitting techniques is presented. Multi-channel ECG signals were recorded and QRS complexes were obtained from every channel and aligned perfectly in matrices. For every channel, the covariance matrix was calculated from the QRS complex data matrix of many heartbeats.

Imaging of bioelectric sources in the heart using a cellular automaton model.

The approach to solve the inverse problem of electrocardiography presented here is using a computer model of the individual heart of a patient. It is based on a 3D-MRI dataset. Electrophysiologically important tissue classes are incorporated using rules.

Electron correlation: the many-body problem at the heart of chemistry.

The physical interactions among electrons and nuclei, responsible for the chemistry of atoms and molecules, is well described by quantum mechanics and chemistry is therefore fully described by the solutions of the Schrödinger equation. In all but the simplest systems we must be content with approximate solutions, the principal difficulty being the treatment of the correlation between the motions of the many electrons, arising from their mutual repulsion. This article aims to provide a clear understanding of the physical concept of electron correlation and the modern methods used for its approximation.

An improved method for angular-resolved characterization of the optical anisotropy of pyrolytic carbon.

A description is given of an experimental technique that improves the accuracy of the measurement of light extinctions by polarized light microscopy from deposits of pyrolytic carbon. The measurements were performed using a specially developed digital photometric image-analysis procedure providing high spatial and angular resolution of light extinctions over the reflecting optical domains with a high dynamic range of grey levels. The digital image acquisition and data processing are illustrated using circular-shaped pyrolytic carbon matrices of infiltrated carbon fibre felts and planar layers of pyrolytic graphite.

Density Functional Theory Study of the Formation of Naphthalene and Phenanthrene from Reactions of Phenyl with Vinyl- and Phenylacetylene.

Reaction pathways for polycyclic aromatic hydrocarbon growth from reactions of either vinyl- or phenylacetylene with a phenyl radical are proposed and investigated using density functional theory (DFT). B3LYP/TZVP calculations are performed to obtain structures of minima and saddle points as well as kinetic data, supplemented with BMK/TZVP single-point energy calculations. The pathways include a cis-trans isomerization via a radicalic four-membered ring intermediate, which has so far not been considered in the literature.

Catalytic C-C bond formation accomplished by selective C-F activation of perfluorinated arenes.

The first example of a catalytically active system for Suzuki-type cross-coupling reactions of perfluorinated arenes such as octafluorotoluene and decafluorobiphenyl is presented.

Structural relaxation made simple.

We introduce a simple local atomic structure optimization algorithm which is significantly faster than standard implementations of the conjugate gradient method and often competitive with more sophisticated quasi-Newton schemes typically used in ab initio calculations. It is based on conventional molecular dynamics with additional velocity modifications and adaptive time steps. The surprising efficiency and especially the robustness and versatility of the method is illustrated using a variety of test cases from nanoscience, solid state physics, materials research, and biochemistry.

Biologically inspired walking machines: design, control and perception.

This article presents a set of methods used to support the design and control of biologically inspired walking machines. Starting with a description of the general system design idea, an example for the design of the mechanical construction, a computer supported design procedure for the control architecture and the description of a three-dimensional world model to be used as knowledge base is given. The focus of this paper is on the engineering and integration process and the interrelation between the different phases of the design process.

An unexpected new optimum in the structure space of DNA solubilizing single-walled carbon nanotubes.

Here we report quantitative data on the amount of single-walled carbon nanotubes that can be suspended with oligodeoxynucleotides in aqueous buffer, together with rate constants for the thermal denaturation of the resulting DNA-nanotube complexes at elevated temperatures. Sequence motifs d(GT)n and d(AC)n with n=2, 3, 5, 10, 20, or 40 were employed, both individually and as equimolar mixtures of the complementary strands. Unexpectedly, the greatest suspending efficiency was found for the mixture of short, complementary oligonucleotides d(GT)3 and d(AC)3.

Three-dimensional silicon inverse photonic quasicrystals for infrared wavelengths.

Quasicrystals are a class of lattices characterized by a lack of translational symmetry. Nevertheless, the points of the lattice are deterministically arranged, obeying rotational symmetry. Thus, we expect properties that are different from both crystals and glasses.

Automated synthesis of heterocycles on solid supports.

The creation of novel diverse heterocycle libraries is an indispensable requirement of modern drug discovery processes. Currently, library sizes of over 10,000 discrete compounds are viable using programmed synthesis on solid supports. This review discusses the recent advances in the automated solid-phase syntheses of heterocycles to generate libraries of bioactive products, and illustrates library sizes that have been obtained, robots used for production of libraries, points of diversity and number of steps on the resin.

Electrochemical microstructuring with short voltage pulses.

The application of short (nanosecond) voltage pulses between a tool electrode and a work piece immersed in an electrolyte solution allows the three-dimensional machining of electrochemically active materials with submicrometer resolution. The method is based on the finite charging time constant of the double-layer capacitance, which varies approximately linearly with the local separation between the electrode surfaces. Hence, the polarization of the electrodes during short pulses and subsequent electrochemical reactions are confined to regions where the electrodes are in sufficiently close proximity.

Turbulent hydrodynamic stress induced dispersion and fragmentation of nanoscale agglomerates.

High pressure dispersion nozzles of 2.5-10 mm length and 125 microm diameter have been characterized in terms of fluid dynamics and dispersion experiments at 100-1400 bar. Elongational stresses at the nozzle entry (5 x 10(5) Pa) and turbulent stresses up to 10(5) Pa at a Reynolds number of 25,000 in turbulent channel flow are identified crucial for desagglomeration and aggregate fragmentation.

One-photon photodetachment of I- in glycerol: spectra and yield of solvated electrons in the temperature range 329

Solvated electrons in glycerol were generated via a resonant one-photon photodetachment of the charge-transfer-to-solvent (CTTS) band of I- in glycerol (Gl) after irradiation with a 248 nm excimer laser. Optical absorption spectra of solvated electrons (esolv-) in Gl were recorded as a function of temperature (381 View Article and Find Full Text PDF

Ferrocenyldiselenolate-stabilized copper-selenium clusters.

The silylated ferrocenyl selenium reagent 1,1'-Fe(eta5-C5H4SeSiMe3)2 has been used for the high yield formation of the phosphine-ligated copper complexes Cu2(fcSe2)(PiPr3)2 (1) and Cu4(fcSe2)2(PnPr3)4 (2) from solublilized CuOAc, as determined by single-crystal X-ray diffraction. The incorporation of a source of Se2- into the reaction scheme with the reagent Se(SiMe3)2 yields the mixed selenide/ferrocenyldiselenolate cluster [Cu20Se6(Se2fc)4(PnPr3)10] (3). Partial substitution of the PnPr3 ligand shell in 3 with the phosphinothiol Ph2P(CH2)3SH leads to an expansion of the framework and the high yield formation of the crystallographically characterized cluster Cu36(fcSe2)6Se12(PnPr3)10(Ph2P(CH2)3SH)2 (5), which contains surface alkylthiol groups on a copper-selenium core.

Basis-set extensions for two-component spin-orbit treatments of heavy elements.

The accuracy of standard basis sets of quadruple-zeta and lower quality for the use in two-component self-consistent field procedures including spin-orbit coupling is investigated for the elements In-I and Au-At. Spin-orbit coupling leads to energetic and spatial splittings of inner shells, which are not described accurately with standard basis sets optimized for scalar relativistic calculations. This results in large errors in total atomic energies and significant errors in atomization energies of compounds containing these atoms.

The missing link between cardiovascular rhythm control and myocardial cell modeling.

Cardiac arrhythmia is currently investigated from two different points of view. One considers ECG bio-signal analysis and investigates heart rate variability, baroreflex control, heart rate turbulence, alternans phenomena, etc. The other involves building computer models of the heart based on ion channels, bio-domain models and forward calculations to finally reach ECG and body surface potential maps.

Visualization of astaxanthin localization in HT29 human colon adenocarcinoma cells by combined confocal resonance Raman and fluorescence microspectroscopy.

Astaxanthin, a carotenoid found in plants and seafood, exhibits antiproliferative, antioxidant and anticarcinogenic properties. We show that astaxanthin delivered with tetrahydrofuran is effectively taken up by cultured colon adenocarcinoma cells and is localized mostly in the cytoplasm as detected by confocal resonance Raman and broad-band fluorescence microspectroscopy image analysis. Cells incubated with beta-carotene at the same concentration as astaxanthin (10 microM) showed about a 50-fold lower cellular amount of beta-carotene, as detected by HPLC.

Current density imaging by pulsed conduction electron spin resonance.

In analogy with Nuclear MRI, the ESR signal phase shift of conduction electrons moving in electrical currents along controlled magnetic field gradients can be used to generate spatial electronic current density maps. First two-dimensional images of the current density distribution in quasi-one-dimensional organic conductors are presented.

EELS investigations of different niobium oxide phases.

Electron energy loss spectra in conjunction with near-edge fine structures of purely stoichiometric niobium monoxide (NbO) and niobium pentoxide (Nb2O5) reference materials were recorded. The structures of the niobium oxide reference materials were checked by selected area electron diffraction to ensure a proper assignment of the fine structures. NbO and Nb2O5 show clearly different energy loss near-edge fine structures of the Nb-M4,5 and -M2,3 edges and of the O-K edge, reflecting the specific local environments of the ionized atoms.

A comparison of linear and nonlinear correlation factors for basis set limit Møller-Plesset second order binding energies and structures of He2, Be2, and Ne2.

The basis set limit Møller-Plesset second-order equilibrium bond lengths of He2, Be2, and Ne2, accurate to 0.01a0, are computed to be 5.785a0, 5.