Novel π2s+π2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene

A new, easy and rapid synthesis of γ‐dilactones is cis‐fused with a cyclopentenic ring via cyclization of 7‐chlorotriethylenic‐malonic acids. The key step implicates an intramolecular cyclization to a cyclopentenyl cation, according to an electrocyclic π_2s + π_2a conrotatory process. This cyclopentenyl cation led to unstable γ‐lactones intermediates that are rearrange to more stable isomers. δ‐lactones (6Z and 6E‐(3‐chlorobut‐2‐en‐2‐yl)‐5‐methyl‐3,6‐dihydro‐2H‐pyran‐2‐one) were obtained as secondary products. Mechanistic pathways were considered. The structures of the newly synthesized compounds were established by elemental and spectral data.     

Mannose‐6‐Phosphate Receptor: A Target for Theranostics of Prostate Cancer

The development of personalized and non‐invasive cancer therapies based on new targets combined with nanodevices is a major challenge in nanomedicine. In this work, the over‐expression of a membrane lectin, the cation‐independent mannose 6‐phosphate receptor (M6PR), was specifically demonstrated in prostate cancer cell lines and tissues. To efficiently target this lectin a mannose‐6‐phosphate analogue was synthesized in six steps and grafted onto the surface of functionalized mesoporous silica nanoparticles (MSNs). These MSNs were used for in vitro and ex vivo photodynamic therapy to treat prostate cancer cell lines and primary cell cultures prepared from patient biopsies. The results demonstrated the efficiency of M6PR targeting for prostate cancer theranostic.     

Polar Diketopyrrolopyrrole‐Imidazolium Salts as Selective Probes for Staining Mitochondria in Two‐Photon Fluorescence Microscopy

Three rationally designed polar derivatives of diketopyrrolopyrrole consisting of 1,3‐dimethylimidazolium cationic units and benzene, thiophene, or furan rings as π spacers were synthesized and thoroughly studied. The obtained salts are soluble in polar organic solvents and show satisfactory solubility in water, which makes them suitable for the applications in bioimaging. Photophysical measurements revealed that the obtained derivatives are characterized by strong absorption and good fluorescence quantum yields. The corresponding two‐photon properties were also examined and showed that the synthesized salts exhibit large two‐photon absorption cross‐sections reaching 4000 GM (GM=Goeppert‐Mayer unit, 1 GM=10^?50 cm⁴ s photon^?1) and very high two‐photon brightness values exceeding 2000 GM. It was demonstrated that these salts can be safely applied in two‐photon fluorescence microscopy for selective staining of mitochondria in living cells.     

New cyclen-cored dendrimers functionalized with pyrene: Synthesis characterization,optical and photophysical properties

New cyclen (1,4,7,10-teraazacyclododecane) cored dendrimers up to the second generation, functionalized with 4, 8 and 16 pyrene units, respectively, were synthesized following a convergent procedure. All new compounds were characterized by NMR spectroscopies and ESI or MALDI TOF mass spectrometry. The optical and photophysical properties of the new dendrimers were studied in THF solution. Absorption spectra showed the typical absorption bands of pyrene moieties. In the fluorescence spectra, monomer as well as excimer emission were observed for all compounds. An increased proportion of excimer emission was observed in the dendrimer of the highest generation.     

Probing the Structural Dynamics of a Bacterial Chaperone in Its Native Environment by Nitroxide-Based EPR Spectroscopy

One of the greatest current challenges in structural biology is to study protein dynamics over a wide range of timescales in complex environments, such as the cell. Among magnetic resonances suitable for this approach, electron paramagnetic resonance spectroscopy coupled to site-directed spin labeling (SDSL-EPR) has emerged as a promising tool to study protein local dynamics and conformational ensembles. In this work, we exploit the sensitivity of nitroxide labels to report protein local dynamics at room temperature. We demonstrate that such studies can be performed while preserving both the integrity of the cells and the activity of the protein under investigation. Using this approach, we studied the structural dynamics of the chaperone NarJ in its natural host, Escherichia coli. We established that spin-labeled NarJ is active inside the cell. We showed that the cellular medium affects NarJ structural dynamics in a site-specific way, while the structural flexibility of the protein is maintained. Finally, we present and discuss data on the time-resolved dynamics of NarJ in cellular context.     

Comparison of open digestion methods and selection of internal standards for the determination of Rh,Pd and Pt in plant samples by ICP-MS

An analytical procedure for the reliable determination of Pd, Pt and Rh in plant samples by inductively coupled plasma-mass spectrometry (ICP-MS) was developed. An ultrasonic nebulizer (USN) was used for sample introduction to improve sensitivity. Under various synthetic plant sample matrix compositions, it was established experimentally that moderate amounts (0.2–2%) of dissolved solids decreased the analyte signals significantly. Internal standardisation with In (for Pd and Rh) and Ir (for Pt) proved to be essential for obtaining correct results. Five open digestion approaches, used for converting solid plant samples to aqueous solution, were also tested for the purpose, namely dry-ashing, dry-ashing followed by HF attack, wet digestion with H₂O₂–HNO₃, wet digestion followed by HF attack and aqua regia digestion. Recovery tests in two spiked plant materials showed that only wet digestions must be used. With these ways, all PGEs could be reliably quantified by USN-ICP-MS without applying a separation or preconcentration step with a good precision (below 10% RSD). The aqua regia procedure was applied to the determination of PGEs in various plant matrices collected along a highway. Results showed that mosses were probably the best choice of samples to monitor the bioaccumulation of PGEs in time.     

Determination of Am and Cm in spent nuclear fuels by isotope dilution inductively coupled plasma mass spectrometry and isotope dilution thermal ionization mass spectrometry after separation by high-performance liquid chromatography

Elemental and isotopic determination of americium and curium in spent nuclear fuels is necessary to validate neutronic calculation codes and for nuclear waste disposal purposes. Prior to mass spectrometric analysis, it is mandatory to perform separations in order to eliminate isobaric interferences between U, Pu, Am and Cm. In the spent fuels samples analyzed, a separation of U and Pu has been first realized with an anion-exchange resin. Then a rapid Am/Cm separation has been developed by high-performance liquid chromatography (HPLC) with an on-line detection using the Am and Cm α-emission. The influence of the different parameters on the chromatographic separation are described and discussed. Inductively coupled plasma mass spectrometry (ICP-MS) and thermal-ionization mass spectrometry (TIMS) have been used to measure the isotopic composition of U, Am and Cm and to determine the ²⁴¹Am/²³⁸U and ²⁴⁴Cm/²³⁸U ratios with the double spike isotope dilution method. The measurement procedures and the accuracy and precision of the results obtained with a quadrupole ICP-MS on different spent fuels samples are discussed and compared with those obtained by TIMS, used as a reference technique. Received: 30 November 1998 / Revised: 8 January 1999 / Accepted: 12 January 1999     

Activities and thermodynamic excess properties of aqueous 2,5-dimethylpyridine mixtures near the critical demixing point: Comparison with 2,6-dimethylpyridine-water mixtures

Activities of 2,5-dimethylpyridine in aqueous solution have been measured at eleven temperatures, two below and nine above the lower critical temperature of the mixture, by the dynamic method of Randall and Weber. Gibbs free energy, enthalpy and entropy are derived to obtain excess quantities and all the results are discussed in connection with the liquid-liquid phase separation, the critical situation and the association properties of the molecules. A comparison is also made with the aqueous 2,6-dimethylpyridine system. A new version of the phase diagram is proposed.     

Towards minimal assumptions for the infimal convolution regularization

We encompass the Moreau-Yosida regularization process by infimal convolution into a general framework. This sheds light on the assumptions required for obtaining the usual properties. In particular the class of lower-T² mappings is shown to be a suitable class for performing the usual proximal regularization in open subsets of Hilbert spaces. The role of growth conditions is pointed out.