Photolyse von 5-Joduracil in wäßriger, sauerstoffgesättigter Lösung

Bei der UV-Photolyse (λ= 254 nm) von 5-Joduracil (C =5·10-4 Mol/l) in wäßriger, sauerstoffgesättigter Lösung bildet sich als organisches Produkt nur Isodialursäure. Daneben entsteht elementares Jod. H2O2 wird nicht gefunden. Bei pH =1 (H2SO4) liegt neben dem elementaren Jod zusätzlich Jod in einer höheren Oxydationsstufe vor, das aus Jodid Jod frei macht und in dessen Gegenwart zugesetztes H2O2 rasch abgebaut wird. Unter besonderen Bedingungen wird nach der Photolyse bei pH =1 sehr wenig H2O2 gefunden, welches beim Stehenlassen rasch aus der Lösung verschwindet.

In Anwesenheit von Jodid (C=5·10-4 Mol/l) entsteht bei pH=3,5 (H2SO4) nur Isodialursäure und zwei Äquivalente Jod. Jod in einer anderen Wertigkeitsstufe wird nicht gefunden.

UV-Photolyse von 5-Joduracil, IV Reaktionen des Uracilradikals mit primären und sekundären Alkoholen in wäßriger, sauerstoffgesättigter Lösung / Photochemistry of 5-Iodouracil in Aqueous Oxygenated Solution in Presence of Primary and Secondary Alcohols

UV-Photolysis (λ=254 nm) of 5-iodouracil in aqueous oxygenated solution in presence of ethanol, ethylene glycol and i-propanol was investigated at pH = 6. Isodialuric acid, uracil, H2O2 and iodine were found in all solutions. In addition to the above products in presence of ethanol, ethylene glycol and i-propanol acetaldehyde, glycolaldehyde and acetone respectively were formed. The yields of these products were determined as a function of the alcohol concentrations. The results suggest that the primary step is a homolytic splitting of the C-I-bond forming a uracil radical and an iodine atom. The uracil radical reacts with oxygen to form isodialuric acid and with alcohols to give uracil and an alkylhydroxyradical. The ratio of the rate constants between the addition of oxygen and the H-atom abstraction of the uracil radical has been determined for the following H-donors: ethanol, ethylene glycol, i-propanol and glycerine (Table 1). The reactions of the alkylhydroxyradicals with oxygen give the corresponding aldehyde or ketone respectively and H2O2. In the absence of oxygen the UV-photolysis of iodouracil in the presence of i-propanol leads to uracil, acetone and iodide. Consideration of the material balance leads to a reaction scheme which explains all the final products.

UV-Photolyse von 5-Bromuracil in wäßriger Lösung / UV-Photolysis of 5-Bromouracil in Aqueous Solution

UV-Photolysis (254 nm) of 5-bromouracil in aqueous solution in the presence of oxygen was investigated at pH = 6. Isodialuric acid and 4,5-dihydroxy-imidazolidone-2 as a secondary photoproduct were identified. The bromine atom from the homolytic splitting of the C-Br-bond and molecular bromine have no effect on the product distribution under our experimental conditions. In the presence of 2-deoxy-D-ribose and oxygen the UV-photolysis of bromo-uracil leads to uracil, isodialuric acid and 4,5-dihydroxy imidazolidone-2. The yield of uracil increases with increasing deoxy-D-ribose concentration while the yield of isodialuric acid and 4,5-dihydroxy-imidazolidone decreases.

Photolyse von 5-Joduracil in wäßriger, sauerstoffgesättigter Lösung in Gegenwart von Methanol / Photochemistry of 5-Iodouracil in Aqueous Solution in Presence of Oxygen and Methanol

UV-Photolysis of aqueous solution of 5-iodouracil in presence of oxygen and methanol leads quantitatively to isodialuric acid, uracil, formaldehyde, H2O2 and iodine. The yields of these products were determined as a function of methanol concentration. The results suggest that the primary step is the homolytic splitting of the C-I-bond. The reaction of the uracil radical with methanol gives uracil and a CH2OH-radical, and with oxygen isodialuric acid. The uracil radical reacts 24 times faster with oxygen than with methanol. The reaction of CH2OH-radical with oxygen gives formaldehyde and H2O2.

Identifizierung der Radiolyseprodukte

Nach 60-Co-γ-Bestrahlung von wäßrigen, sauerstoffhaltigen 5-Bromuracil-Lösungen wurden fünf Verbindungen isoliert und identifiziert: Diisobarbitursäure, Isodialursäure, Alloxan, Isobarbitursäure und Harnstoff.

Aqueous dispersions of organogel nanoparticles - potential systems for cosmetic and dermo-cosmetic applications

OBJECTIVE

The preparation and physicochemical characterization of organogel nanoparticles dispersed in water have been developed. These systems could be employed as nanocarrier for cosmetic applications or as hydrophobic reservoirs for drug delivery.

METHODS

Gelled particles of organic liquid and 12-hydroxystearic acid (organogelator) were obtained by hot emulsification (T>Tgel), with a surfactant (acetylated glycol stearate) and polymers (sodium hyaluronate and polyvinyl alcohol) as stabilizing agents, and cooling at room temperature (T<Tgel). An organic UVB sunscreen molecule, obtained by microwave activation, was used as a hydrophobic model molecule. The physicochemical properties of the starting organogel (gelation tests; rheological study) and the dispersed gelled particles (rheological study; particle mean size, size distribution, zeta-potential measurements; physical stability evaluation; UVB absorption and water resistance ability) were studied. The synthesis of sunscreen compound using microwave activation was also described.

RESULTS

According to the gelation test results, organogels were obtained with various organic liquids. Vaseline and almond oils were selected as organic medium for the gelled nanoparticle preparation. A preliminary formulation study was carried out in order to determine the optimal experimental conditions to obtain stable nanoparticle dispersions. Gelled nanoparticles contained the sunscreen model molecule, with mean size of 450 nm, polydispersity index of 0.18 and zeta-potential value above -30 mV, were obtained by ultrasound probe homogenization method. A comparative study of their dispersion ageing showed a greatly enhanced stability after gelation. According to the UVB absorption evaluation, gelled particles improved the photoprotective ability and the photostability of immobilized UVB blocker. They showed a high water resistance (~83%) even after 40 min of immersion.

CONCLUSION

The obtained results demonstrate the interest of these gelled nanoparticles and their aqueous dispersion for the preparation of new formulations for cosmetic and dermo-cosmetic applications.

None of the known different fibroblast growth-factor receptor-2 carboxy-terminal tails are restricted to cancer-cells

Fibroblast growth factor receptor-2 cDNAs derived from healthy tissues code for proteins with a 63 amino acid carboxy-terminal tail. Some cDNAs isolated from human tumour cDNA libraries code for receptors with 11, 15 or 29 amino acid carboxy-terminal tails. However, the important issue as to whether these latter tails are tumour specific markers has remained unresolved. We show that mRNAs coding for FGFR-2 proteins with carboxy-terminal tails of 11, 29 and 63 amino acids are co-expressed not only in many tumour tissues but also in normal human tissues, while the 15 amino acid tail appears to reflect a cloning artefact.