Label-free selective DNA detection with high mismatch recognition by PNA beacons and ion exchange HPLC

Two 11mer peptide nucleic acid (PNA) beacons were synthesized and tested for the detection of full-matched or single mismatched DNA. Fluorescent measurements carried out in solution showed only partial discrimination of the mismatched sequence, while using anion-exchange HPLC, in combination with fluorimetric detection, allowed DNA analysis to be performed with high sensitivity and extremely high sequence selectivity. Up to >90 : 1 signal discrimination in the presence of one single mismatched base was observed. The analysis was tested on both short and long DNA oligomers. Detection of DNA obtained from PCR amplification was also performed allowing the selective detection of the target sequence in complex mixtures. Label free detection of the DNA with high sequence selectivity is therefore possible using the present approach.     

Breakable Hybrid Organosilica Nanocapsules for Protein Delivery

The direct delivery of specific proteins to live cells promises a tremendous impact for biological and medical applications, from therapeutics to genetic engineering. However, the process mostly involves tedious techniques and often requires extensive alteration of the protein itself. Herein we report a straightforward approach to encapsulate native proteins by using breakable organosilica matrices that disintegrate upon exposure to a chemical stimulus. The biomolecule‐containing capsules were tested for the intracellular delivery of highly cytotoxic proteins into C6 glioma cells. We demonstrate that the shell is broken, the release of the active proteins occurs, and therefore our hybrid architecture is a promising strategy to deliver fragile biomacromolecules into living organisms.     

Pt–rare earth catalysts for ethanol electrooxidation: modification of polyol synthesis

Journal of Solid State Electrochemistry - Pt–Ln/C (Ln = La, Ce, Pr, and Eu) catalysts were obtained by using a modification of the polyol method and tested for ethanol oxidation. Transmission...     

Isolated heterometallic Cr7Ni rings grafted on Au(111) surface

A study of the deposition of heterometallic antiferromagnetically coupled rings onto gold surfaces is reported. Two new {Cr7Ni} rings, [NH2nPr2][Cr7NiF8(3-tpc)16] (1) (where 3-tpc=3-thiophenecarboxylate) and [nBuNH2CH2CH2SH] [Cr7NiF8(O2CtBu)16] (2) have been made and structurally characterized. They have been deposited from the liquid phase on Au(111) and the adsorbed molecules compared by means of scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS). In both cases a two-dimensional distribution of individually accessible {Cr7Ni} heterometallic rings on the gold surface has been obtained, exploiting the direct grafting of sulfur-functionalized clusters. There is a competition between the chemisorption of the {Cr7Ni} clusters and a thiolic self-assembled monolayer (SAM) formed by free ligands. In 2, the presence of a single sulfur ligand should force the molecule to graft with the ring axis normal to the surface. The cluster stability in the STM images and the S-2p energy positions demonstrate, for both functionalizations, the strength of the grafting with the gold surface.     

Flavonoids: chemical properties and analytical methodologies of identification and quantitation in foods and plants

Flavonoids have been recognised as one of the largest and most widespread groups of plant secondary metabolites, with marked antioxidant properties. The general name flavonoid refers to a class of more than 6500 molecules based upon a 15-carbon skeleton. In this paper a general overview of flavonoids, their classification, structures and analytical methods for their determination is presented.     

Photon-graviton amplitudes from the effective action

We report on the status of an ongoing effort to calculate the complete one-loop low-energy effective actions in Einstein-Maxwell theory with a massive scalar or spinor loop, and to use them for obtaining the explicit form of the corresponding M-graviton/N-photon amplitudes. We present explicit results for the effective actions at the one-graviton four-photon level, and for the amplitudes at the one-graviton two-photon level. As expected on general grounds, these amplitudes relate in a simple way to the corresponding four-photon amplitudes. We also derive the gravitational Ward identity for the 1PI one-graviton-N photon amplitude.     

Antiproton reflection by a solid surface

The AE?IS experiment (Antimatter Experiment: Gravity, Interferometry, Spectroscopy (Drobychev et al., 2007)), aims at directly measuring the gravitational acceleration g on a beam of cold antihydrogen ( $\overline{\rm H}$ ). After production, the $\overline{\rm H}$ atoms will be driven to fly horizontally with a velocity of a few 100 m/s for a path length of about 1 meter. The small deflection, few tens of μm, will be measured using two material gratings coupled to a position-sensitive detector working as a Moiré deflectometer similarly to what has been done with atoms (Oberthaler et al., Phys Rev A 54:3165, 1996). Details about the detection of the $\overline{\rm H}$ annihilation point at the end of the flight path with a position-sensitive microstrip detector and a silicon tracker system will be discussed.     

Characterization and hydrogenation of methyl oleate over Ru/TiO2, Ru–Sn/TiO2 catalysts

The hydrogenation of methyl oleate over 2%Ru/TiO₂, 4.7%Sn/TiO₂ and 2%Ru–4.7%Sn–TiO₂ catalysts was studied. The catalysts were prepared by the impregnation method. The characterization techniques used were: (i) specific surface area (B.E.T. method); (ii) pore volume and mean pore diameter; (iii) thermogravimetric analysis (TGA); (iv) temperature programed reduction (TPR); (v) X-ray diffraction (DRX); and (vi) scanning electron microscopy (SEM). The results indicate that the presence of tin increases the difficulty of the ruthenium reduction, evidencing a possible metal–metal interaction. However, tin addition to the TiO₂ and the catalysts calcinations did not significantly influence the values obtained for the surface area and mean pore diameter. The DRX analyses showed that the catalysts have a crystalline structure, mostly in the anatase form. The metal-support interaction occurred probably due to the formation of RuTi of Ru/TiO₂ catalyst. In Ru–Sn/TiO₂ catalyst, the metal–metal interaction occurs between ruthenium and tin, resulting in Ru₃Sn₇. The catalysts reaction revealed that tin addition in ruthenium affects the activity of catalyst considerably in the hydrogenation of methyl oleate reaction. However, the activity decrease is accompanied by a considerable increase of alcohols yield, in particular of unsaturated alcohols.     

Squeezing flow of semi liquid foods between parallel Teflon coated plates

Samples of commercial tomato paste, low fat mayonnaise and mustard about 6–8 mm thick were squeezed to 0.8 mm at various speeds between 5 mm min⁻¹ and 25 mm min⁻¹ between Teflon-coated parallel plates 127 mm in diameter using an Instron UTM Model 5542. All the log force vs log height relationships had a clearly identified linear region. This indicated that a dominant squeezing flow regime was achieved at about 3 mm height, and that the machine has the proper stiffness to perform the tests. The stress level at a pre-selected height in this region is a measure of consistency, sensitive enough to distinguish between products of different brands. The residual stress after relaxation for about 2 min was on order of 10–50% of the initial stress, an indication that all three foods have a considerable structural integrity. In all three products there was a considerable discrepancy between the observed rate effects and predictions based on a pseudoplastic (power law) model. It could be described by the empirical relation (F_v1 − F_R)/(F_v2 − F_R)=(V₁/V₂)^m where F_v1 and F_v2 are the forces at the given displacement reached at speeds v₁ and v₂ respectively, F_R is the residual force after relaxation (found to be practically rate independent), and m is a constant of the order of 0.15–0.33, independent of the compression velocities ratio but characteristic of the food and brand. The calculated elongational viscosity was not a unique function of biaxial strain rate. To a certain extent, this was probably due to imperfect lubrication. But it was also a manifestation of these products considerable structural integrity which cannot be accounted for by models developed for ideal liquids. Received: 1 November 1999 Accepted: 2 May 2000