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161.
Mariana P. Serrano Claudio D. Borsarelli Andrés H. Thomas 《Photochemistry and photobiology》2013,89(6):1456-1462
Biopterin (Bip) and its photoproducts 6‐formylpterin (Fop) and 6‐carboxypterin (Cap) accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder where the protection against UV radiation fails because of the lack of melanin. These compounds absorb in the UV‐A inducing a potential photosensitizing action that can cause damage to DNA and other biomolecules. In this work, we have investigated the capability of these pterin derivatives (Pt) to act as photosensitizers under UV‐A irradiation for the degradation of 2′‐deoxyadenosine 5′‐monophosphate (5′‐dAMP) in aqueous solutions, as model DNA target. Steady‐state and time‐resolved experiments were performed and the effect of pH was evaluated. The results showed that photosensitized degradation of 5′‐dAMP was only observed under acidic conditions, and a mechanistic analysis revealed the participation of the triplet excited state of the pterin derivatives (3Pt*) by electron transfer yielding the corresponding pair of radical ions (Pt?? and 5′‐dAMP?+), with successive photosensitizer recovery by electron transfer from Pt?? to O2. Finally, 5′‐dAMP?+ participates in subsequent reactions to yield degradation products. 相似文献
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163.
Tanay Chattopadhyay Cláudia Reis Paulo André António Teixeira 《Optics Communications》2012,285(9):2266-2275
A novel scheme for an all-optical clocked D flip-flop, with very low complexity, is proposed and numerically demonstrated. This new flip-flop configuration is based on a semiconductor optical amplifier — Mach–Zehnder interferometer (SOA-MZI), with a feedback loop, and presents two stable states determined by the phase shift between the two MZI arms. 相似文献
164.
A one-pot procedure to difunctionalized fused tricyclic bispyrroloquinone derivatives involving the condensation of N-tosylindoledione and α-ketoamines is described. 相似文献
165.
We prove a version of a small index property theorem for strong amalgamation classes. Our result builds on an earlier theorem by Lascar and Shelah (in their case, for saturated models of uncountable first-order theories). We then study versions of the small index property for various non-elementary classes. In particular, we obtain the small index property for quasiminimal pregeometry structures. 相似文献
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168.
János B. Czirok Ákos Tarcsay Pál D. Mezei András Simon László Balázs 《Supramolecular chemistry》2013,25(10-12):722-728
The size limit of substituents allowing O-through-the-annulus rotation of substituted calix[4]arenes was further extended to the propargyloxy group in 24-propargyloxy-25,26,27-tris(N,N-dimethylcarbamoylmethoxy)-p-tert-butylcalix[4]arene by demonstrating its free but slow motion affording equilibrium between the partial cone and 1,2-alternate conformers. The effect of solvent and upper rim substituents R1 on the conformational inversion was investigated by means of 1H NMR. The rotational isomerisation of the parent (R1 = H) analogue could not unambiguously be detected. The experimental results were supported by comprehensive density functional theory studies. 相似文献
169.
Massimo Curini Francesco Epifano Maria Carla Marcotullio Ornelio Rosati Monia Rossi André Tsadjout 《合成通讯》2013,43(17):3181-3187
Layered zirconium hydrogen phosphonate exchanged with the potassium ion was found to be an efficient heterogeneous catalyst for the hydrolysis of sterically hindered phenolic silyl ethers. 相似文献
170.