Multifunctional gold nanoparticle-peptide complexes for nuclear targeting

The ability of peptide-modified gold nanoparticles to target the nucleus of HepG2 cells was explored. Five peptide/nanoparticle complexes were investigated, particles modified with (1) the nuclear localization signal (NLS) from the SV 40 virus; (2) the adenovirus NLS; (3) the adenovirus receptor-mediated endocytosis (RME) peptide; (4) one long peptide containing the adenovirus RME and NLS; and (5) the adenovirus RME and NLS peptides attached to the nanoparticle as separate pieces. Gold nanoparticles were used because they are easy to identify using video-enhanced color differential interference contrast microscopy, and they are excellent scaffolds from which to build multifunctional nuclear targeting vectors. For example, particles modified solely with NLS peptides were not able to target the nucleus of HepG2 cells from outside the plasma membrane, because they either could not enter the cell or were trapped in endosomes. The combination of NLS/RME particles (4) and (5) did reach the nucleus; however, nuclear targeting was more efficient when the two signals were attached to nanoparticles as separate short pieces versus one long peptide. These studies highlight the challenges associated with nuclear targeting and the potential advantages of designing multifunctional nanostructured materials as tools for intracellular diagnostics and therapeutic delivery.     

Dynamic NMR line-shape analysis demonstrates that the villin headpiece subdomain folds on the microsecond time scale

There is considerable interest in small proteins that fold very rapidly. These proteins have become attractive targets for both theoretical and computational studies. The independently folded 36-residue villin headpiece subdomain has been the subject of a number of such studies and is predicted to fold quickly. We demonstrate using dynamic NMR line-shape analysis that the protein folds on the time scale of 10 mus. Folding rates were directly estimated between 56 and 78 degrees C using resolved protein resonances from three different residues at both 500 and 700 MHz. The rates estimated using different residues and different field strengths agree well with each other. The estimated folding rate lies between 0.5 and 2.0 x 105 s-1 over this temperature range. The folding rate depends only weakly on temperature.     

Del Pezzo orders on projective surfaces

In this paper, we generalise the notion of del Pezzo surfaces to orders on surfaces. We show that these del Pezzo orders have del Pezzo centre if the centre is normal Gorenstein and the order has finite representation type. We proceed to classify these del Pezzo orders. The main result is that if the centre is not or the quadric cone, then these del Pezzo orders can be obtained from del Pezzo orders on . Finally, we classify del Pezzo orders on and the quadric cone.     

Laser-induced temperature jump electrochemistry on gold nanoparticle-coated electrodes

Laser-induced temperature jumps (LITJs) at gold nanoparticle-coated indium tin oxide (ITO) electrodes in contact with electrolyte solutions have been measured using temperature-sensitive redox probes and an infrared charge-coupled device. Upon irradiation with 532 nm light, interfacial temperature changes of ca. 20 degrees C were recorded for particle coverages of ca. 1 x 1010 cm-2. In the presence of a redox molecule, LITJ yields open-circuit photovoltages and photocurrents that are proportional to the number of particles on the surface. When ssDNA was used to chemisorb nanoparticles to the ITO surface, solution concentrations as low as 100 fM of target ssDNA-modified nanoparticles could be detected at the electrode surface.     

A new copper acetate-bis(oxazoline)-catalyzed, enantioselective Henry reaction

A highly enantioselective, nitroaldol reaction catalyzed by a chiral Cu(II) bis(oxazoline) complex has been developed. The reaction scope includes both aromatic and aliphatic aldehydes (15 examples) affording products in good yields and enantioselectivities (87-94% ee). An X-ray structure of the catalyst has been provided along with a rationalization of the sense of asymmetric induction.     

Synthesis of new,pyrene-containing,metal-chelating lipids and sensing of cupric ions

The syntheses of several saturated, pyrene-containing, metal-chelating lipids are described. These lipids are capable of strongly binding to transition metal ions employing the metal-chelating headgroup. The excimer-to-monomer ratio of the pyrene groups changes with addition of cupric ions to the liposomes. Three other transition metal ions (Zn(2+), Ni(2+), and Hg(2+)) did not cause any appreciable changes in the excimer-to-monomer ratio. [reaction--see text]     

Diels-Alder reactions of 5-vinyl-1-acyl-2-aryl-2,3-dihydro-4-pyridones: regio- and stereoselective synthesis of octahydroquinolines

[reaction: see text] Readily available 5-vinyldihydropyridones 2 undergo Diels-Alder cyclization with various dienophiles to afford novel octahdroquinolines. The process is highly stereoselective and provides heterocyclic products containing synthetically useful functionality.     

Immunomagnetic separation and detection of Salmonella cells using newly designed carriers

A new method for simultaneous determination of alkoxyethanols (2-methoxyethanol, 2-ethoxyethanol, 2-isopropoxyethanol, and 2-butoxyethanol) by high-performance liquid chromatography (HPLC) with fluorescence detection has been developed. The alkoxyethanols and an internal standard (2-phenoxyethanol) were derivatized by treatment with 1-anthroylnitrile to give the anthroyl esters. The esterification was completed in 30 min in the presence of quinuclidine as base catalyst at room temperature. After stopping the reaction, an aliquot of the final solution was injected into the HPLC. The resulting anthroyl esters of the alkoxyethanols and the internal standard were separated on a C18 reversed-phase column with acetonitrile-water-acetic acid (65:35:0.1, v/v) as the mobile phase and detected fluorimetrically at excitation and emission wavelengths of 360 nm and 460 nm, respectively. The detection limits of the derivatives as alkoxyethanols at a signal-to-noise ratio of 3 were in the range of 1-3 pg per injection. The minimal amounts of alkoxyethanols derivatized in the reaction mixture for derivatization to determine the limits of detection were approximately 0.5 ng. This HPLC method was applied to the determination of some of alkoxyethanols in the air of the workplace where the thinner containing alkoxyethanols was used for painting.     

Bubble particle heterocoagulation under turbulent conditions

An analytical model that enables the calculation of the flotation rate constant of particles as a function of particle size with, as input parameters, measurable particle, bubble, and hydrodynamic quantities has been derived. This model includes the frequency of collisions between particles and bubbles as well as their efficiencies of collision, attachment, and stability. The generalized Sutherland equation collision model and the modified Dobby-Finch attachment model developed previously for potential flow conditions were used to calculate the efficiencies of particle-bubble collision and attachment, respectively. The bubble-particle stability efficiency model includes the various forces acting between the bubble and the attached particle, and we demonstrate that it depends mainly on the relative magnitude of particle contact angle and turbulent dissipation energy. The flotation rate constants calculated with these models produced the characteristic shape of the flotation rate constant versus particle size curve, with a maximum appearing at intermediate particle size. The low flotation rate constants of fine and coarse particles result from their low efficiency of collision and low efficiencies of attachment and stability with gas bubbles, respectively. The flotation rate constants calculated with these models were compared with the experimental flotation rate constants of methylated quartz particles with diameters between 8 and 80 micro m interacting with gas bubbles under turbulent conditions in a Rushton flotation cell. Agreement between theory and experiment is satisfactory.