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Enantio-uracil dinucleotide 5, which consists of two l-uridylic acids and one pyrophosphate, was synthesized for the first time in our laboratory. Benzolyated l-uridine was prepared by a stereoselective glycosylation of silylated uracil with l-1-O-acetyl-2,3,5-tri-O-benzoylribose (l-ABR 7). After deprotection, l-uridine 9 was converted to P1,P4-di(l-uridine 5′-) tetraphosphate tetrasodium salt (l-UP4U 5) by treatment of l-UMP morpholidate 10c with triethylammonium pyrophosphate (TEA-PPi 11b). Spectral data of synthesized l-UP4U 5 are given in the references. All spectral data were identical with those of UP4U 3 except the specific rotation, which showed a positive value compared to UP4U 3 having a negative value. Furthermore, the separation by chiral column chromatography was investigated. 相似文献
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DNA repair has received heightened attention in recent years as ozone depletion threatens to significantly increase DNA damage by UVB radiation[1—6]. The major lesions formed in DNA by this radiation are cis-syn cyclobutane pyrimidine dimers, which are created by the linkage of two neighboring pyrimidine bases in DNA via C5-C5 and C6-C6 atoms by [2+2] cycloaddition[2,5—8]. This potentially lethal or mutagenic damage can be repaired either by the removal of the damaged bases by excisio… 相似文献
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W. Russ Algar 《Analytica chimica acta》2010,673(1):1-25
A comprehensive review of the development of assays, bioprobes, and biosensors using quantum dots (QDs) as integrated components is presented. In contrast to a QD that is selectively introduced as a label, an integrated QD is one that is present in a system throughout a bioanalysis, and simultaneously has a role in transduction and as a scaffold for biorecognition. Through a diverse array of coatings and bioconjugation strategies, it is possible to use QDs as a scaffold for biorecognition events. The modulation of QD luminescence provides the opportunity for the transduction of these events via fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET), charge transfer quenching, and electrochemiluminescence (ECL). An overview of the basic concepts and principles underlying the use of QDs with each of these transduction methods is provided, along with many examples of their application in biological sensing. The latter include: the detection of small molecules using enzyme-linked methods, or using aptamers as affinity probes; the detection of proteins via immunoassays or aptamers; nucleic acid hybridization assays; and assays for protease or nuclease activity. Strategies for multiplexed detection are highlighted among these examples. Although the majority of developments to date have been in vitro, QD-based methods for ex vivo biological sensing are emerging. Some special attention is given to the development of solid-phase assays, which offer certain advantages over their solution-phase counterparts. 相似文献
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Ya Liu Hai‐Li Zhang Guo‐Song Lai Ai‐Min Yu Yu‐Mei Huang De‐Yan Han 《Electroanalysis》2010,22(15):1725-1732
Novel magnetic chitosan‐coated microspheres (MCMSs) were prepared by modifying carbon‐coated iron magnetic nanoparticles with chitosan. An amperometric dihydronicotinamide adenine dinucleotide (NADH) sensor was constructed based on immobilizing MCMS on the surface of a polythionine (PTH) modified glassy carbon electrode (GCE). The fabrication of MCMS/PTH film and its electrocatalytic effect on electrochemical oxidation of NADH were investigated by electrochemical impedance spectroscopy (EIS) and voltammetric methods. It was found that the resulting integrated films of PTH and MCMS exhibit high electrocatalytic response to NADH by significantly reduce its overpotential. The effects of the experimental variables on the amperometric determination of NADH such as solution pH and working potential were investigated for optimum analytical performance. This electrochemical sensor had a fast response to NADH which was less than 10 s. Linear response ranges of 2–10 μM and 10–100 μM and a detection limit of 0.51 μM (S/N=3) were obtained under the optimum conditions. Moreover, the selectivity, stability and reproducibility of this biosensor was evaluated with satisfactory results. 相似文献
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Carotenoids are essential pigments in natural photosynthesis. They absorb in the blue–green region of the solar spectrum and transfer the absorbed energy to (bacterio-)chlorophylls, and so expand the wavelength range of light that is able to drive photosynthesis. This process is an example of singlet–singlet energy transfer and so carotenoids serve to enhance the overall efficiency of photosynthetic light reactions. Carotenoids also act to protect photosynthetic organisms from the harmful effects of excess exposure to light. In this case, triplet–triplet energy transfer from (bacterio-)chlorophyll to carotenoid plays a key role in this photoprotective reaction. In the light-harvesting pigment–protein complexes from purple photosynthetic bacteria and chlorophytes, carotenoids have an additional role, namely the structural stabilization of those complexes. In this article we review what is currently known about how carotenoids discharge these functions. The molecular architecture of photosynthetic systems will be outlined to provide a basis from which to describe the photochemistry of carotenoids, which underlies most of their important functions in photosynthesis. Then, the possibility to utilize the functions of carotenoids in artificial photosynthetic light-harvesting systems will be discussed. Some examples of the model systems are introduced. 相似文献
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《Acta Crystallographica. Section C, Structural Chemistry》2017,73(7):531-535
3‐Aminocarbonyl‐1‐benzylpyridinium bromide (N‐benzylnicotinamide, BNA), C13H13N2O+·Br−, (I), and 1‐benzyl‐1,4‐dihydropyridine‐3‐carboxamide (N‐benzyl‐1,4‐dihydronicotinamide, rBNA), C13H14N2O, (II), are valuable model compounds used to study the enzymatic cofactors NAD(P)+ and NAD(P)H. BNA was crystallized successfully and its structure determined for the first time, while a low‐temperature high‐resolution structure of rBNA was obtained. Together, these structures provide the most detailed view of the reactive portions of NAD(P)+ and NAD(P)H. The amide group in BNA is rotated 8.4 (4)° out of the plane of the pyridine ring, while the two rings display a dihedral angle of 70.48 (17)°. In the rBNA structure, the dihydropyridine ring is essentially planar, indicating significant delocalization of the formal double bonds, and the amide group is coplanar with the ring [dihedral angle = 4.35 (9)°]. This rBNA conformation may lower the transition‐state energy of an ene reaction between a substrate double bond and the dihydropyridine ring. The transition state would involve one atom of the double bond binding to the carbon ortho to both the ring N atom and the amide substituent of the dihydropyridine ring, while the other end of the double bond accepts an H atom from the methylene group para to the N atom. 相似文献