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Directed evolution of excited state lifetime and brightness in FusionRed using a microfluidic sorter.
Integrative Biology ( IF 1.5 ) Pub Date : 2018-09-17 , DOI: 10.1039/c8ib00103k
Premashis Manna 1 , Sheng-Ting Hung , Srijit Mukherjee , Pia Friis , David M Simpson , Maria N Lo , Amy E Palmer , Ralph Jimenez
Affiliation  

Green fluorescent proteins (GFP) and their blue, cyan and red counterparts offer unprecedented advantages as biological markers owing to their genetic encodability and straightforward expression in different organisms. Although significant advancements have been made towards engineering the key photo-physical properties of red fluorescent proteins (RFPs), they continue to perform sub-optimally relative to GFP variants. Advanced engineering strategies are needed for further evolution of RFPs in the pursuit of improving their photo-physics. In this report, a microfluidic sorter that discriminates members of a cell-based library based on their excited state lifetime and fluorescence intensity is used for the directed evolution of the photo-physical properties of FusionRed. In-flow measurements of the fluorescence lifetime are performed in a frequency-domain approach with sub-millisecond sampling times. Promising clones are sorted by optical force trapping with an infrared laser. Using this microfluidic sorter, mutants are generated with longer lifetimes than their precursor, FusionRed. This improvement in the excited state lifetime of the mutants leads to an increase in their fluorescence quantum yield up to 1.8-fold. In the course of evolution, we also identified one key mutation (L177M), which generated a mutant (FusionRed-M) that displayed ∼2-fold higher brightness than its precursor upon expression in mammalian (HeLa) cells. Photo-physical and mutational analyses of clones isolated at the different stages of mutagenesis reveal the photo-physical evolution towards higher in vivo brightness.

中文翻译:


使用微流体分选器定向演化 FusionRed 中的激发态寿命和亮度。



绿色荧光蛋白 (GFP) 及其蓝色、青色和红色对应物由于其遗传可编码性和在不同生物体中的直接表达,作为生物标记物具有前所未有的优势。尽管在设计红色荧光蛋白 (RFP) 的关键光物理特性方面已经取得了重大进展,但相对于 GFP 变体,它们的表现仍然不够理想。 RFP 的进一步发展需要先进的工程策略,以改善其光物理性能。在本报告中,微流体分选器根据激发态寿命和荧光强度来区分基于细胞的库中的成员,用于 FusionRed 光物理特性的定向演化。荧光寿命的流内测量采用频域方法,采样时间为亚毫秒级。有前途的克隆通过红外激光的光力捕获进行分选。使用这种微流体分选仪,产生的突变体比其前身 FusionRed 具有更长的寿命。突变体激发态寿命的改善导致其荧光量子产率增加至 1.8 倍。在进化过程中,我们还发现了一个关键突变(L177M),它产生了一种突变体(FusionRed-M),在哺乳动物(HeLa)细胞中表达时,其亮度比其前体高约2倍。在诱变的不同阶段分离的克隆的光物理和突变分析揭示了向更高体内亮度的光物理进化。
更新日期:2018-08-10
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