Dipping-Induced Azimuthal Helix Orientation in Langmuir-Blodgett Monolayers of α-Helical Amphiphilic Diblock Copolypeptides

The azimuthal helix orientation of the rigid-rod amphiphilic diblock copolypeptides (PLGA-b-PMLGSLGs) of poly(α-L-glutamic acid) (PLGA) and poly(γ-methyl-L-glutamate-ran-γ-stearyl-L-glutamate) with 30 mol % of stearyl substituents (PMLGSLG) in Langmuir-Blodgett (LB) monolayers was investigated using polarized transmission Fourier transform infrared spectroscopy. The relative position of dipping with respect to the previous transfer position can be used to manipulate the azimuthal orientation of the helices parallel to or tilted by an angle of 45° with respect to the dipping direction in the transferred films. The study of the azimuthal order for the LB monolayers of PLGA-b-PMLGSLGs of various block lengths revealed that the observed effect arises mainly from the deformation of the PMLGSLG top brush layer, induced by the flow orientation around the transfer region. In those cases where the PMLGSLG block is tilted by a sufficiently large angle with respect to the surface normal, high azimuthal order parameters of 0.5-0.75 were obtained.

Imaging of inflammatory and infectious diseases in the temporal bone.

Item does not contain fulltextInflammatory and infectious diseases of the temporal bone are a major indication to perform high-resolution CT and MR imaging studies. Such studies allow one to evaluate the extent of the disease in the soft tissues and in the bony structures of the temporal bone. On these same imaging studies the possible extension of the infection to surrounding regions is visualized. In this article a segmental approach is used, focusing on four structures in the temporal bone: the external ear, the otomastoid and petrous apex, the inner ear, and the facial nerve. For each of the four sections imaging findings are described and illustrated, and if relevant a differential diagnostic approach is highlighted

On-chip immunoassay using electrostatic assembly of streptavidin-coated bead micropatterns

We propose an original concept for a sandwich immunoassay that is completely performed on-chip using streptavidin-coated beads as substrate. The latter are electrostatically self-assembled on aminosilane micropatterns at the bottom of a microfluidic channel. We use mouse IgG diluted in phosphate buffered saline (PBS) with 1% bovine serum albumin (BSA) solution as target antigen. The fluorescent sandwich immunocomplex is formed on the beads during the operation of the chip both in stop-flow and continuous-flow modes. Target mouse IgG antigen is detected down to a concentration of 15 ng/mL in stop-flow mode and 250 pg/mL in continuous-flow mode, using only 1300 nL of sample volume. We also demonstrate the possibility of simultaneous detection of two different antigens in a PBS−BSA solution using a dual microfluidic channel structure

Relation entre structure et propriétés électriques d'un complexe à transfert de charge en films de langmuir-blodgett

Un édifice moléculaire stratifié a été élaboré par la technique Langmuir-Blodgett avec des molécules N-docosylpyridinium, TCNQ. Ce complexe à transfert de charge a été synthétisé au laboratoire. Les films L.B. obtenus sont isolants. L'addition in situ d’iode les rend conducteurs (σ = 10—1 ohm—1 cm—1). Les spectres IR et UV-visible ont permis de suivre les différentes étapes d'oxydo-réduction jusqu'au stade final conducteur (TCNQ- partiellement oxydé en TCNQ°). Les modifications structurales correspondantes ont été suivies par diffraction de rayons X. La transition isolant-conducteur s'accompagne d'une mise en ordre du réseau

CHOLEST-6-EN-11-BETA, 19-EPOXY-3-BETA, 5-ALPHA, 8-ALPHA, 9-ALPHA-TETROL, A NOVEL POLYOXYGENATED STEROID FROM THE SPONGE DYSIDEA-TUPHA

Cholest-6-en-11β,19-epoxy-3β,5α,8α,9α-tetrol, a new toxic polyoxygenated steroid, was isolated from the sponge D. tupha. Its structure was detd. on the basis of its mass and NMR spectral properties

Imaging of the opacified middle ear

Middle ear opacification on imaging studies performed in a non-traumatic setting mostly reflects chronic inflammatory/infectious disease. In some of these patients an underlying cholesteatoma will be found. High-resolution computed tomography examinations and magnetic resonance imaging are often used in the work-out of the disease. High-resolution computed tomography of the opacified middle ear serves to describe the status of the ossicular chain, and its suspensory apparatus, as well as the status of the tympanic and mastoid wall. When ossicular erosions are visualized, the probability of a present cholesteatoma is about 90%. Whereas high-resolution computed tomography is not able to differentiate cholesteatoma from other types of opacification, magnetic resonance imaging is. The combined use of delayed post-Gd T1-weighted images and non-EPI based DWI seems to be the actual best option on this matter. (C) 2008 Elsevier Ireland Ltd. All rights reserved

A Novel Strategy for the Design of 8-Hydroxyquinolinate- Based Lanthanide Bioprobes That Emit in the Near Infrared Range

A new polydentate tripodal ligand T2soxMe was synthesized to take advantage of the chelating effect of tridentate 8- hydroxyquinolinate subunits. Potentiometric and spectrophotometric titrations reveal seven pKa values of between 3.7 and 10.2. In water, the use of T2soxMe leads to thermodynamically stable and soluble LnIII complexes at physiological pH, with conditional stability constants in the range logb11=7.8..8.6. The chelates are resistant toward hydrolysis and show interesting photophysical properties, particularly in the near infrared (NIR) range. The emission lifetimes of the NdIII and YbIII complexes recorded in D2O and H2O suggest the absence of water molecules in the first coordination sphere of the metal ions. Moreover, the low energy of the triplet state allows efficient energy transfer from the ligand to the metal ions: in water at pH 7.4, the sensitization efficacy of the NIR luminescence reaches 75 and 100% for NdIII and YbIII, respectively, leading to overall quantum yields of 0.027 and 0.13%; ErIII luminescence is also detected. According to the WST-1 test, the YbIII podate at concentrations of up to 250 mm does not display sizeable cytotoxicity for Jurkat cells after 24 h of incubation. Finally, the same podate is shown to couple to human serum albumin, leading to an increase of 50% in the NIR- luminescence intensity

New Opportunities for Lanthanide Luminescence

Trivalent lanthanide ions display fascinating optical properties. The discovery of the corresponding elements and their fist industrial uses were intimately linked to their optical properties. This relationship has been kept alive until today when many high-technology applications of lanthanide-containing materials such as energy -saving lighting devices, displays, optical fibers and amplifiers, lasers, responsive luminescent stains for biomedical analyses and in cellulo sensing and imaging heavily rely on the brilliant and pure-color emission of lanthanide ions. In this review we first outlined the basics of lanthanide luminescence with emphasis on f-f transitions, the sensitization mechanisms, and the assessment of the luminescence efficiency of lanthanide-containing emissive molecular edifices. Emphasis was then put on two fast developing aspects of lanthanide luminescence: materials for telecommunications and light emitting diodes, and biomedical imaging and sensing. Recent advances in NIR- emitting materials for plastic amplifiers and waveguides were described, together with the main solutions brought by researchers to minimize non-radiative deactivation of excited states. The demonstration in 1999 that erbium tris (8-hydroxyquinolinate) displayed a bright green emission suitable for orgenic light emitting diodes (OLEDs) was followed by realizing that in OLEDs, 25% of the excitation energy leads to singlet states and 75% to triplet states. Since lanthanide ions are good triplet quenchers, they now also play a key role in the development of these lighting devices. Luminescence analyses of biological molecules are among the most sensitive analytical techniques known. The long lifetime of the lanthanide excited states allows time- resolved spectroscopy to be used, suppressing the sample autofluorescence and reaching very low detection limits. Not only visible lanthanide sensors are now ubiquitously provided in medical diagnosis and in cell imaging, but the feasibility of using NIR emission of ions such as Ybm is now being tested because of deeper penetration in biological tissues