In cellulo evaluation of phototransformation quantum yields in fluorescent proteins used as markers for single-molecule localization microscopy.

Authors:
Dr. Virgile Adam, PhD
Dr. Virgile Adam, PhD
CNRS / Institute for Structural Biology (IBS)
Research scientist
single molecule fluorescence microscopy, fluorescent protein engineering, X-ray crystallography
Grenoble | France

PLoS One 2014 10;9(6):e98362. Epub 2014 Jun 10.

Université Grenoble Alpes, Institut de Biologie Structurale (IBS), Grenoble, France; CNRS, IBS, Grenoble, France; CEA, DSV, IBS, Grenoble, France.

Single-molecule localization microscopy of biological samples requires a precise knowledge of the employed fluorescent labels. Photoactivation, photoblinking and photobleaching of phototransformable fluorescent proteins influence the data acquisition and data processing strategies to be used in (Fluorescence) Photoactivation Localization Microscopy ((F)-PALM), notably for reliable molecular counting. As these parameters might depend on the local environment, they should be measured in cellulo in biologically relevant experimental conditions. Here, we measured phototransformation quantum yields for Dendra2 fused to actin in fixed mammalian cells in typical (F)-PALM experiments. To this aim, we developed a data processing strategy based on the clustering optimization procedure proposed by Lee et al (PNAS 109, 17436-17441, 2012). Using simulations, we estimated the range of experimental parameters (molecular density, molecular orientation, background level, laser power, frametime) adequate for an accurate determination of the phototransformation yields. Under illumination at 561 nm in PBS buffer at pH 7.4, the photobleaching yield of Dendra2 fused to actin was measured to be (2.5 ± 0.4) × 10(-5), whereas the blinking-off yield and thermally-activated blinking-on rate were measured to be (2.3 ± 0.2) × 10(-5) and 11.7 ± 0.5 s-1, respectively. These phototransformation yields differed from those measured in poly-vinyl alcohol (PVA) and were strongly affected by addition of the antifading agent 1,4-diazabicyclo[2.2.2]octane (DABCO). In the presence of DABCO, the photobleaching yield was reduced 2-fold, the blinking-off yield was decreased more than 3-fold, and the blinking-on rate was increased 2-fold. Therefore, DABCO largely improved Dendra2 photostability in fixed mammalian cells. These findings are consistent with redox-based bleaching and blinking mechanisms under (F)-PALM experimental conditions. Finally, the green-to-red photoconversion quantum yield of Dendra2 was estimated to be (1.4 ± 0.6) × 10(-5) in cellulo under 405 nm illumination.

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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0098362PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4051587PMC
October 2015
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References

(Supplied by CrossRef)
Live-cell super-resolution imaging with synthetic fluorophores
S van de Linde et al.
Annual Review of Physical Chemistry 2012

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