求翻译Cu2+-Selective Ratiometric and “Off-On”

Varioustransition-metalionsarecrucialforthelifeoforganisms.1Amongtheseisthecopperion，whichplaysacriticalroleasacatalyticcofactorforavarietyofmetalloenzymes，includingsuper... Various transition-metal ions are crucial for the life of organisms.1 Among these is the copper ion， which plays a critical role as a catalytic cofactor for a variety of metalloenzymes， including superoxide dismutase， cytochrome c oxidase， and tyrosinase. However， under overloading conditions， copper exhibits toxicity in that it causes neurodegenerative diseases (e.g.， Alzheimer’s and Wilson’s diseases) probably by its involvement in the production of reactive oxygen species.2 Consequently， organisms tightly regulate internal concentrations of copper. Owing to the Janus-faced properties of copper in organisms， numerous efforts have been undertaken to develop efficient and selective methods to assess copper ions in cells and organisms. In addition，copper is a significant metal pollutant due to its widespread use. The toxicity of copper ions for humans is rather low compared to other heavy metals， but certain microorganisms are affected by even submicromolar concentrations of Cu2+.3 Even though fluorescent probes for copper ion have been extensively explored owing to biological significance of this metal ion，4 there are still only a few examples of “off-on” type sensors available in aqueous systems.5 Furthermore， only a few ratiometric fluorescent probes for Cu2+ have been found in the literature due the fluorescence quenching nature of paramagnetic Cu2+，6 and most of them were working only in pure organic solvents. Ratiometric fluorescent measurements observe changes in the ratio of the intensities of the emission at two wavelengths. Thus， ratiometric fluorescent sensors have an important feature that they can be used to evaluate the analyte concentration and provide built-in correction for environmental effects.