Spectrophotometric determination of uranium with 5-(2′-carboxyphenyl)azo-8-quinolinol in the non-ionic micellar medium of Triton X-100

Triton X-100, a non-ionic surfactant, has been used to sensitize the reaction of 5-(2-carboxyphenyl)azo-8-quinolinol with uranium in aqueous medium at pH 5.2–6.1 to form a wine red coloured complex. The micellar sensitization results in two and a half-times enhanced molar absorptivity enabling the determination of uranium in rock samples at ppm level, stability of the complex enhanced from 4 hours to at least 72 hours. Extraction of the complex is avoided making the procedure simple, rapid and easy in operation. The molar absorptivity and Sandell's sensitivity of the complex are 1.50·10⁴l·mol^–1·cm^–1 and 15.9 ng·cm^–2, respectively, at _max=568 nm. Beer's law is obeyed over the range 0–3.3 g·ml^–1 of uranium. An amount as low as 0.19 g·ml^–1 of uranium could be determined satisfactorily within a relative standard deviation of ±1.3%. The limits of determination and practical quantitation are 0.29 and 1.80 ppm, respectively. The method was applied to the determination of uranium in soil, stream sediment and rock samples.     

Molecular orbital calculations on the conformation of nucleic acids and their constituents

The conformational properties of the furanose ring of purine- and pyrimidine--nucleosides and-nucleotides are studied quantum-mechanically with the help of the PCILO method, using the pseudorotational concept. The computations point to the existence of two stable conformational zones centered around the C(3)-endo and C(2)-endo conformations which in the isolated furanose ring are separated by barriers of the order of 4 kcal/mole. In nucleosides one of the barriers (the one running through the O(1)-exo-C(2)-exo path) becomes very high. A detailed study is made of the relation between the phase angle of pseudorotation, P, and the torsion angle about the glycosyl bond, _CN. A very satisfactory agreement with the available experimental data is observed.

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Zusammenfassung Die Konformationseigenschaften des Furanoserings in -Nucleosiden und Nucleotiden von Purin und Pyrimidin werden nach der PCILO-Methode unter Berücksichtigung der pseudorotatorischen Betrachtungsweise studiert. Die Rechnung läßt auf die Existenz zweier stabiler Konformationszonen schließen, die in der Umgebung der C(2)-endo und der C(3)-endo Konformationen liegen, und die im isolierten Furanosering durch Energiebarrieren der Größenordnung von 4 kcal/mol voneinander getrennt sind. In Nucleosiden wird eine der Barrieren (die durch den Weg O(1)-exo-C(2)-exo gekennzeichnete) sehr hoch. Die Relation zwischen dem Phasenwinkel der Pseudorotation, P, und dem Drehwinkel um die Glycosylbindung, _CN, wird einer eingehenden Untersuchung unterworfen. Man beobachtet eine sehr zufriedenstellende Übereinstimmung mit den verfügbaren experimentellen Daten.

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Résumé Les propriétés conformationnelles du noyau furanose des -nucleosides et nucleotides des purines et pyrimidines sont étudiées par la méthode PCILO en faisant appel au concept de la pseudorotation. Les calculs indiquent l'existence de deux zones de conformations stables, centrées autour des conformations C(2)-endo et C(3)-endo, qui sont dans le sucre isolé séparées par des barrières de l'ordre de 4 kcal/mole. Dans les nucleosides, l'une de ces barrières (celle qui passe par le chemin O(1)-exo-C(2)-exo) devient très élevée. Une étude détaillée est effectuée sur la relation entre l'angle de phase de la pseudorotation P et l'angle de torsion autour de la liaison glycosylique, _CN. Un excellent accord avec les données expérimentales disponibles est observé.

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This research was supported by the R.C.P. 173 and the A.T.P. A 655-2303 of the C.N.R.S.     

Preferred conformers in n-propanol: A PCILO study

Preferred conformers around the central C-C and C-O bonds in n-propanol have been determined using the quantum-mechanical PCILO method and compared with those observed experimentally by microwave spectroscopy. The agreement between theory and experiment is excellent, thus minimizing time consuming searches for microwave transitions corresponding to the preferred conformers.     

Molecular orbital studies on the structure of nucleoside analogs. IV. Conformation of 3-deazapurine nucleosides

Conformational properties of 3-deazapurine nucleosides (namely, 3-deazaadenosine and 3-deazaguanosine) have been investigated by the PCILO method. Both C(2′)-endo and C(3′)-endo sugar puckers have been considered and the results indicate that the conformational preferences of these nucleoside analogs are quite different from those of their parent nucleosides adenosine and guanosine, respectively. This result has been correlated in terms of the biological inactivity of these nucleoside analogs.     

Conformation of nucleoside antibiotics

Minor modifications or substitutions in the sugar or in the base part of pyrimidine and purine nucleosides have a profound effect on their biological activity. These modified nucleosides usually become antiviral, antibacterial, or cancerostatic agents and they are collectively called nucleoside antibiotics. The conformational properties of some of these nucleoside antibiotics have been studied by the PCILO method. The results obtained from such study indicate that the conformational preferences of these nucleoside antibiotics are very similar to those of their parent nucleosides and especially so in the situations that occur in aqueous solutions. The important biological significance of these results is that these nucleoside antibiotics can easily get incorporated into growing chains of DNA and RNA by mimicking their parent nucleosides and can interfere with the protein synthesis of RNA or DNA synthesis.     

Emerging Design Principle of Near-Infrared Upconversion Sensitizer Based on Mitochondria-Targeted Organic Dye for Enhanced Photodynamic Therapy

Upconversion luminescent (UCL) triggered photodynamic therapy (PDT) affords superior outcome for cancer treatment. However, conventional UCL materials which all work by a multiphoton absorption (MPA) process inevitably need extremely high power density far over the maximum permissible exposure (MPE) to laser. Here, a one-photon absorption molecular upconversion sensitizer Cy5.5-Br based on frequency upconversion luminescent (FUCL) is designed for PDT. The unusual super heavy atom effect (SHAE) in Cy5.5-Br strongly enhances its spin-orbit coupling (0.23 cm⁻¹), triplet quantum yield (11.1 %) and triplet state lifetime (18.8 μs) while the potential hot-band absorption of Cy5.5-Br is well maintained. Importantly, Cy5.5-Br can efficiently target the tumour site and kill cancer cells by destroying mitochondria under a biosafety MPE to 808 nm laser. The photostability and antitumor results are obviously superior to that of a Stokes process. This work provides a design criterion for FUCL dyes to realize effective PDT upon a biosafety optical density, possibly bringing more clinical benefits than conventional MPA materials.     

Immunomagnetic nanoparticle based quantitative PCR for rapid detection of Salmonella

We have developed a rapid and sensitive method for immunomagnetic separation (IMS) of Salmonella along with their real time detection via PCR. Silica-coated magnetic nanoparticles were functionalized with carboxy groups to which anti-Salmonella antibody raised against heat-inactivated whole cells of Salmonella were covalently attached. The immuno-captured target cells were detected in beverages like milk and lemon juice by multiplex PCR and real time PCR with a detection limit of 10⁴ cfu.mL^?1 and 10³ cfu.mL^?1, respectively. We demonstrate that IMS can be used for selective concentration of target bacteria from beverages for subsequent use in PCR detection. PCR also enables differentiation of Salmonella typhi and Salmonella paratyphi A using a set of four specific primers. In addition, IMS—PCR can be used as a screening tool in the food and beverage industry for the detection of Salmonella within 3–4 h which compares favorably to the time of several days that is needed in case of conventional detection based on culture and biochemical methods.

A Cyanine-based Liposomal Nanophotosensitizer for Enhanced Cancer Chemo-Photodynamic Therapy

Currently, chemotherapy is one of the most important treatment modalities for malignant tumors in the clinic, however, it exhibits some shortcomings, such as poor selectivity, limited efficacy and serious adverse effects. Therefore, synergistic therapy and accurate drug delivery at tumor sites become a promising strategy for achieving tumor eradication. Herein, a smart NIR fluorescence imaging-guided nanoliposome was fabricated by encapsulating a chemotherapeutic drug(doxorubicin, DOX), liposomes(L) and a near-infrared(NIR) photosensitizer(CY) to form L@CY@DOX, which could realize enhanced therapeutic efficacy of chemo-PDT in cancer therapy(PDT=photodynamic therapy). L@CY@DOX can induce mitochondrial apoptosis and produce severe toxicity at the cellular level, and L@CY@DOX can enrich in the tumor site, which significantly induces tumor death. In vitro and in vivo studies demonstrated that L@CY@DOX exhibited great antitumor efficacy compared with each one of these monotherapies, indicating that the combination of chemotherapy and PDT possessed potential development prospects and is anticipated in clinical application.     

Das Größenspektrum des natürlichen atmosphärischen Aerosols

The size distribution of natural occuring aerosol particles with a radius between 10^?5 and 10^?6cm was measured simultaneously by two different methods: Firstly the measurement of the current, caused by the natural distribution of electric charges on the particles, which move along the axis of a cylindrical condenser; secondly the distribution of thoron decay products on the size spectrum of the aerosol. The both methods have their maximum sensitivity in different regions of the size spectrum. The distributions obtained with the two methods are in rather good agreement. The small deviation of the two spectra is ascribed to systematic differences of the measuring methods.