Purine | EPFL Graph Search

La purine est une molécule azotée hétérocyclique constituée d'un cycle pyrimidine fusionné à un cycle imidazole. C'est l'hétérocycle azoté le plus répandu dans la nature. Parmi les neuf tautomères possibles du noyau purine, les formes CH (C2H, C4H, C5H, C6H et C8H), ainsi que les formes N1H et N3H peuvent être négligées car très peu probables (rupture d'aromaticité), seules les formes N7H et surtout N9H (99 %) existent en solution neutre. Le noyau purine nu n'existe pas dans la nature. On trouve en revanche de nombreux dérivés aminés, hydroxylés ou méthylés, souvent sous forme de nucléosides, qui sont inclus dans le terme général purines. Deux des bases nucléiques présentes dans tous les acides nucléiques sont des purines : l'adénine et la guanine. Dans l'ADN, ces bases forment des liaisons hydrogène avec les pyrimidines complémentaires, la thymine et la cytosine. La xanthine, l'hypoxanthine et l'acide urique sont d'autres purines résultant de la dégradation des bas

Novel Chemosensors for Biologically Important Analytes

Ziya Köstereli

In this work, fluorescent-based chemosensors for the detection of important analytes in aqueous solution are described. The sensors are based on different detection concepts, including analyte-induced aggregation/de-aggregation, pattern-based sensing and micelle-based sensing. In chapter 2, we present an analyte-induced aggregation-type chemosensor for the sensing of spermine. A charge-frustrated amphiphile composed of a highly fluorescent pyrene-1,3,6-trisulfonate head group and an eicosane side chain was used as a fluorescence chemosensor. Analyte-induced aggregation of the dye upon addition of spermine results in pronounced fluorescence quenching. The sensor enables the detection of spermine down to the nanomolar concentration range with good selectivity over closely related biogenic amines such as spermidine. In chapter 3, we describe a conceptually new âone-cuvetteâ sensing system for the pattern-based analysis of seven aminoglycosides antibiotics. The antibiotics include amikacin, apramycin, gentamicin, kanamycin A and B, neomycin, and paromomycin. A mixture of two amphiphiles with fluorescent head groups was used as a sensing ensemble. In buffered aqueous solution, the amphiphiles form a dynamic mixture of micellar aggregates. In the presence of aminoglycosides, the relative amount and the composition of the micelles is modified. Accurate differentiation in the low micromolar concentration range is achieved by a principal component analysis of the spectral data. Also, the sensing system allows the differentiation of pure aminoglycosides from their mixtures. In chapter 4, a fluorescent chemosensor based on analyte-induced aggregation/de-aggregation is described for the sensing of Al3+ and citric acid. In buffered aqueous solution, the amphiphilic dye can form aggregates and the aggregation of the dye is associated with a strong quenching of its fluorescence. The Al3+-induced aggregation is used to sense Al3+ in the low micromolar concentration range with high selectivity. Furthermore, we demonstrate that the non-fluorescent dye-Al3+ complex can be used as a sensing ensemble for the detection of citric acid. The assay is able to quantify the citric acid content of commercial beverages such as energy drinks. A simple micelle-based assay for the fluorescence sensing of vitamin K1 is described. In the following chapter 5, the assay enables the detection of vitamin K1 in the low micromolar concentration range. As a sensing ensemble, a mixture of the surfactant triton X-100 and 1 aminopyrene in buffered aqueous solution is employed. Vitamin K1 co-localizes with the fluorescent pyrene dye in the micelle, resulting in fluorescence attenuation by dynamic quenching. The assay displays good selectivity and can be used to determine the concentration of vitamin K1 in a commercial preparation. In chapter 6, a fluorescent-based sensor array for the optical analysis of purine derivatives is described. The array is composed of four polysufonated fluorescent dyes. The complexation of the analytes results in partial quenching of the fluorescence. The Sensor array enables the identification of ten purine derivatives including caffeine, theophylline, theobromine, purine, hypoxanthine, paraxanthine, 8-chlorotheophylline, 6-mercaptopurine, cladribine and penciclovir at low millimolar concentration. Furthermore, it is possible to use the array for obtaining information about the quantity and the purity of samples.

EPFL2015

Array-based sensing of purine derivatives with fluorescent dyes

Ziya Köstereli, Kay Severin

Natural and synthetic purine derivatives such as caffeine, theophylline, 6-mercaptopurine and 8-chlorotheophylline are important drugs. Due to the structural similarity of these compounds, it is intrinsically difficult to prepare chemosensors for their selective optical detection. Here, we describe a sensor array which can be used to differentiate pharmacologically important purine derivatives with good accuracy. The array is composed of four polysufonated fluorescent dyes, all of which can bind purines via π-stacking interactions. The complexation of the analytes results in partial quenching of the fluorescence. The fluorescence response of the four dyes provides a characteristic signal pattern, enabling the identification of thirteen purine derivatives at low millimolar concentration. Furthermore, it is possible to use the array for obtaining information about the quantity and purity of purine samples.

Royal Soc Chemistry2015

Synthesis and pairing properties of 3'-deoxyribopyranose (4' -> 2')-oligonucleotides ('p-DNA')

Damian Ackermann

The prepn. and the pairing properties of the new 3'-deoxyribopyranose (4'->2')-oligonucleotide (= p-DNA) pairing system, based on 3'-deoxy-b-D-ribo-pyranose nucleosides is presented. D-Xylose was efficiently converted to the prefunctionalized 3-deoxyribopyranose deriv. 4-O-[(tert-butyl)dimethylsilyl]-3-deoxy-D-ribo-pyranose 1,2-diacetate (obtained as a 4:1 mixt. of a- and b-D-anomers). From this sugar building block, the corresponding, appropriately protected thymine, guanine, 5-methylcytosine, and purine-2,6-diamine nucleoside phosphoramidites were prepd. in a minimal no. of steps. These building blocks were assembled on a DNA synthesizer, and the corresponding p-DNA oligonucleotides were obtained in good yields after a one-step deprotection under std. conditions, followed by HPLC purifn. Qual., p-DNA shows the same pairing behavior as p-RNA, forming antiparallel, exclusively Watson-Crick-paired duplexes that are much stronger than corresponding DNA duplexes. Duplex stabilities within the three related (i.e., based on ribo-pyranose nucleosides) oligonucleotide systems p-RNA, p-DNA, and 3'-O-Me-p-RNA were compared with each other. Intrinsically, p-RNA forms the strongest duplexes, followed by p-DNA, and 3'-O-Me-p-RNA. However, by introducing the nucleobases purine-2,6-diamine and 5-methylcytosine instead of adenine and cytosine, a substantial increase in stability of corresponding p-DNA duplexes was obsd. [on SciFinder (R)]

2002

Novel Chemosensors for Biologically Important Analytes

Ziya Köstereli

EPFL2015