原文： 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 [79]译文： 91-[2-(3-羧基-9，10-二苯)anthryl]-6 羟基3h-xanthen-3-酮 (dpaxs)使用最广泛的1o2阱9，10-diphenylanthracene(政治部) 而迅速的反应，特别是与1o2形成耐热endoperoxide的增长率为k=3106米1秒 减少6%，为355nm，是用来衡量形成的过氧化物 不过，政治部衍生不是很敏感的探针，因为检测是基于测量吸光度[79] [79]fused审批与fluorophore(fluorescein)以准第一功的特点与第二的荧光特性 fluorescein被选为fluorophore，因为它具有较高的荧光量子产率在水溶液中，并能 兴奋长波长 由此导致的融合 91-[2-(3-羧基-9，10-二苯)anthryl]-6 - 羟基3h-xanthen-3酮(dpaxs)(图11)[79] 因此，dpaxs被化学第一陷阱1o2允许荧光检测 他们的反应与1o2出示dpaxendoperoxides(dpax-eps)(图11) dpaxs自己scarcelyfluoresce，而dpaxeps强烈的荧光 机制的会计核算窄化荧光dpaxs及其增强dpax-办事仍不清楚[79] 荧光强度的荧光素衍生物已知是减少酸性条件下，随着大量的质子 该phenoxide氧原子 为了稳定的荧光强度，在生理pH， 电子撤组wereincorporated在2-和7点位置的xanthene生色 通往cl(dpax-2)和F(dpax-3)(图11) 这个修改降低pKa值的酚氧原子〔79〕 dpax-2检测生产1o2从两个不同的发电系统: 该moo42/过氧化氢体系和3-(4-甲基-1-萘基)丙酸endoperoxide(ep-1)系统， 该法在不同pH值(5和4美元) 在这两种情况下，提高了探头的荧光验证时接触的发电系统 这些调查结果证实dpaxs的优势，在检测1o2在中性或碱性溶液[79] 该行为此探针对双氧水，! NO和O2! 还研究， 但不改变强度的荧光染色任何这些活性物种 这些事实证实特异性这种探针1o2[79] 检测1o2生物样品中为75% 为了这个目的，dpax-2diacetate(dpax-2-da)制成的，因为它被认为是更容易接受细胞 dpax-2-daishydrolysedbyintracellularesterases产生dpax- 双方dpax-2dpax-2da试验，比较在同一实验系统 但是，细胞染色同样，在这两种情况 这个观察可能意味着dpax-2本身也是membranepermeable[79]
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
1In the first study to look at what happens over the years to the billions of pounds of plastic waste floating in the world's oceans， scientists are reporting that plastics — reputed to be virtually indestructible — decompose with surprising speed and release potentially toxic substances into the 2Chemicals are an important aspect in our economy and serves with many However， when chemicals are not properly used they can create a problem with global There is the threat of chemical spills and also a possible use by Many chemicals are stored and processed at numerous If terrorists were to attack any chemical plants in the United States it would kill more than 2 million There is also a long-term threat of contamination that will affect both people and the These chemicals can contaminate the water and cause many illnesses to In 1962， Rachel Carson informed the public about the horrible effects that DDT had on the environment and health problems of But it took 10 years for the United States to ban this But not all chemicals pose a security To reduce the use of chemicals facilities are required to provide the public with annual chemical This has allowed our society to force these facilities to use these chemicals better and The Stockholm Convention on Persistent Organic Pollutants came into effect in May This treaty would ban or restrict the production and use of 12 hazardous There will always be an abundance of chemicals but their use needs to be lowered to make them less of a 3A captain of a ship drunkenly crashes a massive oil tanker along a reef and changes the physical and emotional world Chemical spills are major problems that plague the Strict government regulation is trying to aid with this problem， but governmental leaders face many Disposal of harmful chemicals is often difficult and Since chemical waste has destroyed the environment， steps are being taken to prevent further 看看，参考一下吧：
