A versatile approach towards regioselective platinated DNA sequences

Undesired N(7) platination of 2'-deoxyguanosine residues at predetermined sites in an oligodeoxynucleotide (ODN) sequence is prevented by applying the sterically demanding diphenylcarbamoyl (DPC) as an O(6)-protecting group. The presence of a base-labile oxalyl linker between the immobilized 3'-nucleotide and controlled pore glass (CPG) allows cleavage of the protected ODN from the support and leaves DPC protection unaffected. This method provides an ODN with specifically blocked guanine-N(7) sites for platination. In the hexanucleotides prepared in this study, 5'-GGBGGT-3'(for B=T, C and A), a platinum GG adduct is introduced at G4,G5. These site-specific platinated hexamers were isolated in a yield of 65 %, and were fully characterized by using reversed-phase HPLC (high performance liquid chromotography), LCMS (liquid chromatography-mass spectrometry), MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry), PAGE (polyacrylamide gel electrophoresis) and Maxam-Gilbert sequencing analysis.     

Hydrogen adsorption in carbon nanostructures: comparison of nanotubes, fibers, and coals

Single-walled carbon nanotubes (SWNT) were reported to have record high hydrogen storage capacities at room temperature, indicating an interaction between hydrogen and carbon matrix that is stronger than known before. Here we present a study of the interaction of hydrogen with activated charcoal, carbon nanofibers, and SWNT that disproves these earlier reports. The hydrogen storage capacity of these materials correlates with the surface area of the material, the activated charcoal having the largest. The SWNT appear to have a relatively low accessible surface area due to bundling of the tubes; the hydrogen does not enter the voids between the tubes in the bundles. Pressure-temperature curves were used to estimate the interaction potential, which was found to be 580+/-60 K. Hydrogen gas was adsorbed in amounts up to 2 wt % only at low temperatures. Molecular rotations observed with neutron scattering indicate that molecular hydrogen is present, and no significant difference was found between the hydrogen molecules adsorbed in the different investigated materials. Results from density functional calculations show molecular hydrogen bonding to an aromatic C[bond]C that is present in the materials investigated. The claims of high storage capacities of SWNT related to their characteristic morphology are unjustified.     

Discovery of a potent and highly β1 specific proteasome inhibitor from a focused library of urea-containing peptide vinyl sulfones and peptide epoxyketones

Syringolins, a class of natural products, potently and selectively inhibit the proteasome and show promising antitumour activity. To gain insight in the mode of action of syringolins, the ureido structural element present in syringolins is incorporated in oligopeptide vinyl sulfones and peptide epoxyketones yielding a focused library of potent new proteasome inhibitors. The distance of the ureido linkage with respect to the electrophilic trap strongly influences subunit selectivity within the proteasome. Compounds 13 and 15 are β5 selective and their potency exceeds that of syringolin A. In contrast, 5 may well be the most potent β1 selective compound active in living cells reported to date.     

Automated parallel solid-phase synthesis and anticancer screening of a library of peptide-tethered platinum(II) complexes

The automated parallel solid-phase synthesis of a 36-member library of peptide-tethered platinum(II) complexes is described. The identity and quality of each product were confirmed by mass spectrometry and (1)H NMR. Subsequently, each compound was screened for in vitro anticancer activity by treating the A2780 (human ovarian carcinoma) cell line with two concentrations of the drugs (100 and 10 microM) in quadruplicate. The reduction of cell proliferation induced by the drugs at these concentrations was determined with the MTT colorimetric assay (MTT = 3-(4',5'-dimethylthiazol-2'-yl)-2,5-diphenyltetrazolium bromide) and compared to cisplatin. Even though no very active library members could be identified, five apparently most active (8[1], 8[4], 8[10], 8[13], and 8[24]) and two inactive complexes (8[33] and 8[34]) were purified using gel permeation chromatography and fully characterized by NMR spectroscopy ((1)H, (195)Pt) and MS. The IC(50) values of these complexes and cisplatin in A2780 cells were subsequently determined using the MTT assay in a conventional manner. All seven complexes have an IC(50) above 100 microM, confirming the results generated by the assay at 100 and 10 microM of the crude reaction products.     

Exotic droplets formed in microfluidic chips with uniform wettability

Microdroplets are widely used in industrial processes. In the absence of external forces, droplets generally assume a spherical shape. Here, we present two methods to form non-spherical droplets in microfluidic glass chips. A uniformly hydrophobized chip has been successfully used to dynamically control the width and length of elongated water-in-oil droplets; on a hydrophilic chip, we generated non-spherical double droplets that consisted of two different oils in a water continuous phase.     

Micromechanically tuned ring resonator in silicon on insulator

We demonstrate a monolithically integrated micromechano-optical device where the resonance wavelength of a silicon ring resonator is tuned by perturbing the evanescent field with an electrostatically actuated silicon nitride microcantilever. The resonance wavelength can be tuned over 125 pm.     

Integrated mechano-optical hydrogen gas sensor using cantilever bending readout with a Si3N4 grated waveguide

We demonstrate a proof of concept of a novel and compact integrated mechano-optical sensor for H(2) detection based on a microcantilever suspended above a Si(3)N(4) grated waveguide. The fabricated devices are mechanically and optically modeled and characterized. Sensing operation of the sensor is demonstrated with 1% H(2) in N(2). The error in detection of the cantilever bending induced by absorption of H(2) is estimated to be approximately 10 nm. Significantly improved sensitivity (down to ～33 pm) is expected for reduced initial bending of the microcantilever. The simulation and experimental results are in good agreement and provide a good guideline for further optimization of the sensor.     

Testing Methods for PUF-Based Secure Key Storage Circuits

Design for test is an integral part of any VLSI chip. However, for secure systems extra precautions have to be taken to prevent that the test circuitry could reveal secret information. This paper addresses secure test for Physical Unclonable Function based systems. It investigates two secure Built-In Self-Test (BIST) solutions for Fuzzy Extractor (FE) which is the main component of PUF-based systems. The schemes target high stuck-at-fault (SAF) coverage by performing scan-chain free functional testing, to prevent scan-chain abuse for attacks. The first scheme reuses existing FE blocks (for pattern generation and compression) to minimize the area overhead, while the second scheme tests all the FE blocks simultaneously to minimize the test time. The schemes are integrated in FE design and simulated; the results show that for the first test scheme, a SAF fault coverage of 95 % can be realized with no more than 47.1k clock cycles at the cost of a negligible area overhead of only 2.2 %; while for the second test scheme a SAF fault coverage of 95 % can be realized with 3.5k clock cycles at the cost of 18.6 % area overhead. Higher fault coverages are possible to realize at extra cost (i.e., either by extending the test time, or by adding extra hardware, or a combination of both).     

Contactless charge carrier mobility measurement in organic field-effect transistors

With the increasing performance of organic semiconductors, contact resistances become an almost fundamental problem, obstructing the accurate measurement of charge carrier mobilities. Here, a generally applicable method is presented to determine the true charge carrier mobility in an organic field-effect transistor (OFET). The method uses two additional finger-shaped gates that capacitively generate and probe an alternating current in the OFET channel. The time lag between drive and probe can directly be related to the mobility, as is shown experimentally and numerically. As the scheme does not require the injection or uptake of charges it is fundamentally insensitive to contact resistances. Particularly for ambipolar materials the true mobilities are found to be substantially larger than determined by conventional (direct current) schemes.