那些数据库啊 学校都应该买了的 上本校的图书馆什么的看看 9-[2-(3-Carboxy-9，10-diphenyl)anthryl]-6-hydroxy-3H-xanthen-3-ones (DPAXs) The most widely used 1O2 trap is 9，10-diphenylanthracene (DPA)， which reacts rapidly and specifically with 1O2 to form a thermostable endoperoxide at a rate of k =3106 M1 The decrease in absorbance at 355 nm is used as a measure of the formation of the However， DPA derivatives are not very sensitive probes because the detection is based on the measurement of absorbance [79] Umezaka et [79] fused DPA with a fluorophore (fluorescein) aiming to associate the first’s reactive characteristics with the second’s fluorescent Fluorescein was chosen as fluorophore since it has a high fluorescence quantum yield in aqueous solution and is able to be excited at long From this fusion resulted 9-[2-(3-carboxy-9，10-diphenyl)anthryl]-6- hydroxy-3H-xanthen-3-ones (DPAXs) (F 11) [79] Thus， DPAXs were the first chemical traps for 1O2 that permitted fluorescence They react with 1O2 to produce DPAX endoperoxides (DPAX-EPs) (F 11) DPAXs themselves scarcely fluoresce， while DPAXEPs are strongly The mechanism accounting for the diminution of fluorescence in DPAXs and its enhancement in DPAX-EPs remain unclear [79] The fluorescence intensity of fluorescein derivatives is known to be decreased under acidic conditions as a consequence of the protonation of the phenoxide oxygen In order to stabilize the fluorescence intensity at physiological pH， electron-withdrawing groups wereincorporated at the 2- and 7-positions of the xanthene chromophore， leading to Cl (DPAX-2) and F (DPAX-3) (F 11) This modification lowered the pKa value of the phenolic oxygen atom [79] DPAX-2 was used to detect the production of 1O2 from two different generation systems: the MoO4 2/H2O2 system and the 3-(4-methyl-1-naphthy)propionic acid endoperoxide (EP-1) system， which act at different pH values (5 and 4， respectively) In both cases an increase of the probe’s fluorescence was verified when in contact with the generating These results confirmed DPAXs’ advantage when detecting 1O2 in neutral or basic aqueous solutions [79] The behaviour of this probe towards H2O2， !NO and O2 ! was also studied， but no change in the intensity of the fluorescence was observed for any of these reactive These facts corroborate the specificity of this probe for 1O2 [79] The detection of 1O2 in biological samples was also With this purpose， DPAX-2 diacetate (DPAX-2-DA) was prepared， since it was considered to be more permeable to DPAX-2-DA is hydrolysed by intracellular esterases to generate DPAX- Both DPAX-2 and DPAX-2DA were tested and compared in the same assay However， cells were stained similarly in both This observation probably means that DPAX-2 itself is also membranepermeable
有机化学英语论文Abstract In this work the effects of the microporosity and chemical surfaceof polymeric adsorbents on adsorptive properties of phenol Textural parameters of four kinds of polymeric resins namely AB-8 D4006 NKA-II and D16 resin were separately measuredby ASAP The surface chemistry of these polymeric resins was determined by means of inverse gaschromatography (IGC) and diffusereflectance infrared Fourier transform spectroscopy (DRIFTS) Static equilibrium adsorption experiments were carried out to obtain theisotherms of phenol on the polymeric It was shown that NKA-II and AB-8 resin possessed relatively high BET surface areas andmicropore volumes while D4006 and D16 resin possessed comparatively low BET surface areas and micropore The results of IGCexperiments revealed that NKA-II resin had extraordinary high specific component of the free energy of adsorption both for polar acetone andbenzene probe and thus extraordinary strong surface polarity compared to the other polymeric It was also found that the isotherm ofphenol on NKA-II was much higher than that on the other polymeric resins due to its strongest surface polarity and largest micropore volumeamong four kinds of These experimental observations indicated that adsorption of phenol on the polymeric resins depended greatly ontheir microporosity and surface The well-developed microporosity and the strong surface polarity would improve the adsorptionof phenol on the polymeric 2004 Elsevier BV All rights Keywords: Polymeric resin; Phenol; Porosity; Surface chemistry; Inverse gas chromatography
