Pascale Clivio

Thymine Dimerization in DNA Model Systems : Cyclobutane Photolesion Is Predominantly Formed via the Singlet Channel

UV-induced formation of cylcobutane pyrimidine dimers (CPD) in all thymine DNA models have been studied by femtosecond IR spectroscopy. CPDs are shown to form within approximately 1 ps during the decay of the initially excited (1)pi pi * state. The quantum yields phi(D)(ps) determined after the (1)pi pi * decay equal the final yield phi(D)(cw). This gives evidence for a predominance of the singlet channel in CPD formation.

Spore Photoproduct: A Key to Bacterial Eternal Life

4.4. Formation Mechanism of SPDNA 1219 5. Factors Influencing SPDNA Formation in Spores 1220 5.1. Small Acid-Soluble Spore Proteins 1221 5.2. Dipicolinic Acid 1222 5.3. Pressure/Hydration Level 1222 5.4. Temperature 1222 5.5. Conclusions 1222 6. Artificial Production of SPDNA, SPTIDE, and SPSIDE 1223 6.1. UV Irradiation of Bacterial Vegetative Cells 1223 6.2. UV Irradiation of Isolated DNA 1223 6.2.1. Isolated DNA 1223 6.2.2. Isolated DNA Complexed with R/ -Type SASP 1224

Alkaloids from leaves and root bark ofErvatamia hirta

Abstract During chemical investigation of the leaves and root bark of Ervatamia hirta , 33 alkaloids were isolated. Seven are new: six are the ‘monomeric’ alkaloids ( E ) 16- epi -normacusine B , ( E ) 16- epi -affinisine, O -acetyl-16- epi -affinisine, affinisine- N (4)-oxide, dehydro-16- epi -affinisine, norfluorocurarine- N (4)-oxide, and the seventh is the bisindole 16-decarbomethoxyvoacamine-pseudoindoxyl. The known alkaloids are: ( E ) 16- epi -isositsirikine, β-yohimbine, yohimbine, 19,20-dehydro-β-yohimbine, β-yohimbine-pseudoindoxyl, isositsirikine, 19,20-dihydroisositsirikine, β-yohimbine-oxindole, normacusine B , affinisine, vobasine, dregamine, tabernaemontanine, norfluorocurarine, 12-hydroxynorfluorocurarine, apparicine, 3,14-dihydroellipticine, antirhine, voacristine, ibogaine, i☐ygaine, i☐ygaine-hydroxyindolenine, iboluteine, 4′,17,(17β)-dihydrotchibangensine, 16-decarbomethoxyvoacamine and 19,20-dihydro-16-decarbomethoxyvoacamine. Structural elucidation of the new alkaloids is based on spectral data and chemical correlations.

Alkaloids from leaves and stem bark of Ervatamia polyneura

Abstract Twenty-three alkaloids were isolated from leaves and stem bark of Ervatamia polyneura, four of which are new: vobasenal, 16-epivobasenal, 3-oxo-19-epiheyneanine and 3-hydroxy-3,4-secocoronaridine. The other alkaloids are the known pericyclivine, vobasine, vobasine N-(4)-oxide, 16-epivobasine, vobasinol, dregamine, perivine, anhydrovobasindiol, apparicine, (+) tubotaiwine, voaphylline, 3, 14-dihydroellipticine, coronaridine, eglandine, eglandulosine, heyneanine, 19-epiheyneanine, voacangine and coronaridinehydroxyindolenine. Structural elucidation of the new alkaloids was based on spectral data.

Mechanism of the Decay of Thymine Triplets in DNA Single Strands.

The decay of triplet states and the formation of cyclobutane pyrimidine dimers (CPDs) after UV excitation of the all-thymine oligomer (dT)18 and the locked dinucleotide TLpTL were studied by nanosecond IR spectroscopy. IR marker bands characteristic for the CPD lesion and the triplet state were observed from ∼1 ns (time resolution of the setup) onward. The amplitudes of the CPD marker bands remain constant throughout the time range covered (up to 10 μs). The triplet decays with a time constant of ∼10 ns presumably via a biradical intermediate (lifetime ∼60 ns). This biradical has often been invoked as an intermediate for CPD formation via the triplet channel. The present results lend strong support to the existence of this intermediate, yet there is no indication that its decay contributes significantly to CPD formation.

UV-Induced TA Photoproducts: Formation and Hydrolysis in Double-Stranded DNA

Hydrolysis of TA photoproduct leads to two derivatives presenting different formation kinetic profiles depending on the oligomer content. The formation efficiency of TA photoproducts in UV-C-irradiated DNA slightly exceeds the formation of the trans,syn cyclobutane pyrimidine dimer at TT sites.

Alkaloids from the leaves and stem bark of Ervatamia malaccensis

Abstract Chemical investigation of the leaves and stem bark of Ervatamia malaccensis afforded two novel alkaloids, N (1)-methoxymethuenine and N (1)-methoxy-19,20-dehydroervatamine together with the known alkaloids: 19,20-dehydroervatamine, 20-epiervatamine, methuenine, 16-epimethuenine, 6-oxomethuenine and dregamine. Structural elucidation of the new alkaloids was based on spectral data and on a chemical correlation.

16-epi-silicine, an alkaloid of the ervatamine-type from Pandaca caducifolia

The structures of two ervatamine-type alkaloids previously isolated from Pandaca caducifolia are established as the known silicine and the new 16-epi-silicine after careful NMR analysis of the two compounds and their olefinic derivatives.

Development of new nucleic acid photoaffinity probes : synthesis of 4-thiothymine labelled nucleoside analogues

Abstract The new nucleic acid photoaffinity probes 1a, 1b, 2 and 3 in which a 4-thiothymine is linked at the end of a variable chain introduced at the C-5 position of deoxyuridine have been constructed.

(6-4) photoproduct DNA photolyase mechanistic studies using s5-(6-4) photoproducts

The facile photoreversal reaction, which occurs upon direct irradiation of the thioanalogue of the (6-4) photoproducts of DNA 3, and not from its corresponding Dewar derivative 4, to give the parent dinucleotide 1 models (6-4) photoproduct DNA photolyase repair activity.