Decrease of colocalization between analyzed objects was also indicated by the loss of warm colors in corresponding colocalization maps due to reduced fraction of nMDP values with indexes above zero (fig. Intermediate Icorr values for partial colocalization were as follows: 0.573 for 10-pixel translation, 0.132 for 20-pixel translation, and 0.055 for 30-pixl translation (fig. Icorr values were in range of 1 (for complete colocalization) to 0 (for lack of colocalization) (fig. As a result, we observed gradual decrease of Icorr values that was proportional to the decrease of colocalization between analyzed images. The threshold value for the analysis of all translated objects was set as ‘118’ due to the fact that this was the minimum threshold value that assured complete separation of objects translated by 40 pixels (fig. This set of data with dissimilarly colocalized spheres was then analyzed with Colocalization Colormap to calculate nMDPs distribution and Icorr values (fig. Reduced intensity correlation between pairs of corresponding pixels within generated images was observed proportionally to fewer overlap between objects (fig. Complete colocalization was produced with translation by 0 pixels, whereas partial colocalization was produced with translation by 10, 20, or 30 pixels, and lack of colocalization (separation of the objects) was produced with translation by 40 pixels (fig. The object was represented by a stack of images, that was first duplicated and then all the pixels in the duplicated stack were translated (fig. For that purpose, we have created an artificial spherical object based on a 3D intensity gradient (fig. The proper algorithm implementation was tested on artificial images prepared to simulate complete colocalization, partial colocalization, and lack of colocalization. This innovative method produces a pseudo-color map of correlations between pairs of corresponding pixels in two original input images, thereby offering quantitative visualisation of colocalization. This website contains Colocalization Colormap ImageJ plugin that implements the Jaskolski's algorithm (Jaskolski et al. The disadvantage of methods based on general intensity correlation is lack of information about the spatial distribution of colocalized signals with respect to the composite nature of biological structures within the particular image. A linear, or non-linear relationship among the intensities of both channels might be then assumed. Colocalization studies are widely performed using methods based on global image analysis which for instance involves intensity correlation coefficients such as the Pearson correlation coefficient and the Manders overlap coefficient The general paradigm of these approaches is to plot the pixel values of two images against each other and display the result in a pixel distribution diagram called a scatter plot in a way in which an intensity of the given pixel in the first channel is used as the x-coordinate of the scatter plot and the intensity of the corresponding pixel in the second channel consists its y-coordinate.
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