1 To begin, perform live cell2 single molecule imaging of HaloTag protein condensates. 3 Using ImageJ, convert each channel 4 from the raw imaging data file 5 into an independent TIFF file. 6 If necessary, run pre-tracking comb.
text 7 and follow the prompts 8 to replace any frames with the most recent ones. 9 To load the single molecule of movie file in SlimFast, 10 click on load, followed by image stack. 11 Set the parameters for localization 12 and acquisition under respective option sheets.
13 Visualize the localizations of all the molecules. 14 And using lock all, 15 generate a file containing the localizations 16 of all the molecules in every frame. 17 Next, go to load particle data 18 and select SlimFast to load the file 19 with localization and acquisition settings.
20 Using option and sheet tracking, 21 adjust the parameters for trajectory generation. 22 Click on gen traj to generate a file 23 containing the trajectories of all the molecules. 24 Load the sheet tracked file into eval SPT 25 and set the parameters 26 to filter out the trajectories shorter than 2.5 seconds.
27 Using export data, generate a file 28 with all the filtered trajectories. 29 Running the ImageJ macro, nucleus, 30 and cluster mask version two. text, 31 threshold all the frames of the movie acquired 32 in the JFX549 channel to generate a time lapse movie 33 populated with the time evolving binary mask 34 highlighting condensate locations.
35 Using convert ASCII slow tracking CSS 3. M, 36 reformat the trajectories 37 and run categorization version 4. M 38 to sort them based on the lifetime 39 a molecule spends in a condensate.
40 Next, using plot residence hist CSS. M, 41 extract the observed dissociation rate 42 of specifically bound molecules 43 and the photobleaching rate from the in condensate 44 protein of interest and the H2B trajectories. 45 Finally, calculate the corrected mean residence time 46 of the protein of interest, 47 specifically bound to its condensates.
48 A frame from two-color single molecule movie 49 of TAF15 IDR-Halo-FTH1 shows signals 50 from the nucleus in both PA-JF646 and JFX549 channels. 51 Upon assembling and sorting, 52 a clear distinction was observed for the trajectories 53 of PA-JF646 detected molecules bound to the condensates. 54 The calculated mean residence times 55 after correction for photobleaching 56 were more for TAF15-Halo-FTH1 than Halo-TAF15.
