Chiral poly(ureidophthalimide) foldamers in water

Poly(ureidophthalimide)s decorated with hydrophilic side chains, that ensure solubility in aqueous media, have been synthesized and characterized by UV/Vis and circular dichroism (CD) spectroscopy. Temperature and concentration dependent CD measurements in water have revealed an almost temperature and concentration independent Cotton effect, indicative for a strong intramolecular organization. Similar studies in THF demonstrate the dynamic nature of the secondary architecture, a characteristic of foldamers. In addition, the bisignated Cotton effect in water is opposite in sign to that in THF, suggestive for a solvent-dependent preference for one helical handedness. Mixing experiments prove the dominance of water in determining the handedness of the helical architecture. The solvent allows for control over the helical architecture and thus governs the supramolecular synthesis.     

Bioinformatic analysis of xenobiotic reactive metabolite target proteins and their interacting partners

Background  

Protein covalent binding by reactive metabolites of drugs, chemicals and natural products can lead to acute cytotoxicity. Recent rapid progress in reactive metabolite target protein identification has shown that adduction is surprisingly selective and inspired the hope that analysis of target proteins might reveal protein factors that differentiate target- vs. non-target proteins and illuminate mechanisms connecting covalent binding to cytotoxicity.     

Isomorphisms of groups related to flocks

A truly fruitful way to construct finite generalized quadrangles is through the detection of Kantor families in the general 5-dimensional Heisenberg group over some finite field $\mathbb{F}_{q}$ . All these examples are so-called ??flock quadrangles??. Payne (Geom. Dedic. 32:93?C118, 1989) constructed from the Ganley flock quadrangles the new Roman quadrangles, which appeared not to arise from flocks, but still via a Kantor family construction (in some group of the same order as ). The fundamental question then arose as to whether (Payne in Geom. Dedic. 32:93?C118, 1989). Eventually the question was solved in Havas et?al. (Finite geometries, groups, and computation, pp.?95?C102, de Gruyter, Berlin, 2006; Adv. Geom. 26:389?C396, 2006). Payne??s Roman construction appears to be a special case of a far more general one: each flock quadrangle for which the dual is a translation generalized quadrangle gives rise to another generalized quadrangle which is in general not isomorphic, and which also arises from a Kantor family. Denote the class of such flock quadrangles by . In this paper, we resolve the question of Payne for the complete class . In fact we do more??we show that flock quadrangles are characterized by their groups. Several (sometimes surprising) by-products are described in both odd and even characteristic.     

Characterization of a photonic strain sensor in silicon-on-insulator technology

Recently there has been growing interest in sensing by means of optical microring resonators in photonic integrated circuits that are fabricated in silicon-on-insulator (SOI) technology. Taillaert et al. [Proc. SPIE 6619, 661914 (2007)] proposed the use of a silicon-waveguide-based ring resonator as a strain gauge. However, the strong lateral confinement of the light in SOI waveguides and its corresponding modal dispersion where not taken into account. We present a theoretical understanding, as well as experimental results, of strain applied on waveguide-based microresonators, and find that the following effects play important roles: elongation of the racetrack length, modal dispersion of the waveguide, and the strain-induced change in effective refractive index.     

Cationic Geminoid Peptide Amphiphiles Inhibit DENV2 Protease,Furin, and Viral Replication

Dengue is an important arboviral infectious disease for which there is currently no specific cure. We report gemini-like (geminoid) alkylated amphiphilic peptides containing lysines in combination with glycines or alanines (C₁₅H₃₁C(O)-Lys-(Gly or Ala)_nLys-NHC₁₆H₃₃, shorthand notation C₁₆-KX_nK-C₁₆ with X = A or G, and n = 0–2). The representatives with 1 or 2 Ala inhibit dengue protease and human furin, two serine proteases involved in dengue virus infection that have peptides with cationic amino acids as their preferred substrates, with IC₅₀ values in the lower µM range. The geminoid C₁₆-KAK-C₁₆ combined inhibition of DENV2 protease (IC₅₀ 2.3 µM) with efficacy against replication of wildtype DENV2 in LLC-MK2 cells (EC₅₀ 4.1 µM) and an absence of toxicity. We conclude that the lysine-based geminoids have activity against dengue virus infection, which is based on their inhibition of the proteases involved in viral replication and are therefore promising leads to further developing antiviral therapeutics, not limited to dengue.     

Electrochemically-Switched 2nd Order Non-Linear Optical Response in an Arylimido-Polyoxometalate with High Contrast and Cyclability

Electrochemically switched 2^nd order non-linear optical responses have been demonstrated for the first time in polyoxometalates (POMs), with an arylimido-derivative showing a leading combination of high on/off contrast (94 %), high visible transparency, and cyclability. Spectro-electrochemical and TD-DFT studies indicate that the switch-off results from weakened charge transfer (CT) character of the electronic transitions in the reduced state. This represents the first study of an imido-POM reduced state, and demonstrates the potential of POM hybrids as electrochemically activated molecular switches.