细胞内PH值现在可以通过蛋白质的活体红色荧光成像来测量。采用一般条件下采用440纳米激发光或者在酸性环境下采用585纳米激发光可以获得不同的细胞荧光读数，
细胞内PH值现在可以通过蛋白质的双光红色荧光成像来测量。
作者采用红色荧光探针，成像根据两个激发光获得荧光读数的技术比例就可以读出细胞内PH值。为多颜色多通道成像研究保留了绿色荧光波长的活体通道作为其他细胞特性的研究（如能量代谢等）。作者根据这个特性，细胞采用双光子显微镜可以一秒一秒地跟着活体细胞内pH值变化。双光
参考文献：J. Am. Chem. Soc. doi:10.1021/ja202902d (2011)
生物探索推荐英文摘要：
Nature News: A microscopist’s litmus test
Jun 23,成像 2011 Vol.474
Intracellular pH levels can now be measured with a protein that glows red.
The red fluorescent protein has been dubbed pHRed by its designers, Gary Yellen and his colleagues at Harvard Medical School in Boston, Massachusetts. Light-detecting molecules of pHRed are preferentially excited by light at a wavelength of either 440 nanometres in basic conditions or 585 nanometres in acidic conditions, and the excitation ratio of the two gives a read-out of pH.
pHRed’s fluorescence lifetime — the time between excitation and emission — also responds to pH. The authors used this feature in two-photon microscopy to track second-by-second pH changes in living cells.
A red pH sensor leaves the often-used green fluorescence wavelength available for simultaneous study of other cellular properties, such as energy metabolism, during multicolour imaging.
Reference: J. Am. Chem. Soc. doi:10.1021/ja202902d (2011)
美国哈佛大学医学院神经生物学系Gary Yellen等研究者最近研发了基因编码的技术红色荧光蛋白质pHRed在活体细胞内成像pH值的技术。
pHRed的活体荧光寿命（从光激发到荧光发射的时间）也跟pH值有关。
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