Synthesis of 2'-deoxyguanosine from 2'-deoxyadenosine via C2 nitration.

An efficient synthetic method has been developed for the synthesis of 2'-deoxyguanosine from the more commercially available 2'-deoxyadenosine via late-stage C2 nitration in 48.7% total yield by a 5-step synthetic procedure. Crucially, 2'-deoxyadenosine was fully protected by bennzoyl groups and then nitrated at C2 by tetrabutylammonium nitrate/trifluoroacetic anhydride. The resulting 2-NO2 moiety was converted into 2-NH2 by Ni-catalyzed hydrogenolysis. Finally, 2'-deoxyguanosine was obtained from the diaminopurine intermediate by deaminase-catalyzed reaction. Furthermore, the 2-NO2 moiety also appeared to be a versatile handle to introduce a variety of functional groups, resulting in a divergent access to 2-substituted 2'-deoxyadenosine analogues.

[Epidemic condition and biological characteristics of non-O1/non-O139 Vibrio cholerae in Haizhu District of Guangzhou].

OBJECTIVE: To understand the epidemic condition, distribution and biological characteristics of non-O1/non-O139 Vibrio cholerae from 2001 to 2009 in Haizhu District, to provide a scientific basis for the prevention and control of acute diarrhea. METHODS: Referring to the detecting method written in "Cholera control handbook" in the fifth edition, 764 specimens from outside environment (including the water in the Pearl River, drinking water, water for breeding fish, aquatic products and delicatessen foods), 189 specimens of healthy population and 3398 intestinal samples of patients with diarrhea, summing up to 4351 specimens for non-O1/non-O139 Vibrio cholerae test. RESULTS: 4,351 specimens were detected of 101 strains of non O1/non O139 Vibrio cholerae, the total detection rate was 2.32%; 66 strains were identified by serotyping and grouped into 26 different serotypes, the typing rate was 65.3%. The strains VBO9, VBO38 and VBO76 were the dominant bacteria.Nine strains of the same type of non-O1/non-O139 Vibrio cholerae were found from external environments also from patients with diarrhea, suggesting that there might be a correlation between the two. CONCLUSION: Non-O1/non-O139 Vibrio cholerae have diversified serotypes, causing certain infection rate among the population in this region. These bacteria exist extensively in external environment and they are the potential hazard to the citizens.

[Multiplayer white organic light-emitting diodes with different order and thickness of emission layers].

In multilayer OLED devices, the order and thickness of the emission layers have great effect on their spectrum. Based on the three basic colours of red, blue and green, a series of white organic light-emitting diodes(WOLEDS)with the structure of ITO/CuPc(12 nm)/NPB(50 nm)/EML/LiF(1 nm)/Al(100 nm) and a variety of emission layer's orders and thicknesses were fabricated. The blue emission material: 2-t-butyl-9,10-di-(2-naphthyl)anthracene (TBADN) doped with p-bis(p-N, N-diphenyl-amono-styryl)benzene(DSA-Ph), the green emission material: tris-[8-hydroxyquinoline]aluminum(Alq3) doped with C545, and the red emission material: tris-[8-hydroxyquinoline]aluminum( Alq3) doped with 4-(dicyanomethylene)-2-t-butyl-6-(1, 1, 7, 7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) were used. By adjusting the order and thickness of each emission layer in the RBG structure, we got a white OLED with current efficiency of 5.60 cd x A(-1) and Commission Internationale De L'Eclairage (CIE) coordinates of (0. 34, 0.34) at 200 mA x cm(-2). Its maximum luminance reached 20 700 cd x m(-2) at current density of 400 mA x cm(-2). The results were analyzed on the basis of the theory of excitons' generation and diffusion. According to the theory, an equation was set up which relates EL spectra to the luminance efficiency, the thickness of each layer and the exciton diffusion length. In addition, in RBG structure with different thickness of red layer, the ratio of th e spectral intensity of red to that of blue was calculated. It was found that the experimental results are in agreement with the theoretical values.

[Multiple emissions in organic electroluminescent device using a mixed layer as an emitter].

A organic electroluminescent device has been fabricated by using a mixed layer as an emitter. The configuration of the device is ITO/TPD/TPD: PBD(equimole)/PBD/A1, in which TPD (N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine) and PBD (2-(4'-biphenyl)-5-(4''-tert-butylphenyl)-1,3,4-oxadiazole) are used as hole transport material and electron transport material, respectively. Broad and red-shifted electroluminescent spectra related to the fluorescence of constituent materials were observed. It is suggested that the monomer, exciplex and electroplex emissions are simultaneously involved in EL spectra by comparison of the EL with the PL spectra and decomposition of the EL spectrum. The type of exciplex is the interaction between the excited state TPD (TPD*) and PBD in the ground state, and the type of electroplex is a (D+-A-)* complex by cross-recombination of hole on the charged hole transport molecule (D+) and electron on the charged electron transport molecule (A-). All types of excited states show different formation mechanisms and recombination processes under electric field. The change of emission strengths from monomer and excited complexes lead to a blue-shift of the emissive spectra with an increasing electric field. The maximum luminance and external quantum efficiency of this device are 240 cd x (cm2)(-1) and 0.49%, respectively. The emissions from exciplex or electroplex formation at the organic solid interface generally present a broad and red-shifted emissive band, providing an effective method for tuning of emission color in organic electroluminescent devices.