PLX file

Purpose of PLX file

A PLX file links the pattern of clusters found during analysis to named analytes.   In addition to its primary purpose of identifying the analytes, the PLX file can also specify the concentration of the top dilution of the analyte for use with a standard curve.

After data from an imager or cytometer has been analyzed, the particles have codes which can be visualized in two dimensions. 

Each particle has an "X" code, corresponding to the yellow intensity at the end of the particle that has the highest green intensity, and a "Y" code, corresponding to the yellow intensity at the end of the particle that has an intermediate green intensity.   (Green fluorescence is at its lowest in the center of the particle, where analytes are intended to bind).

Particles with probes for the same analyte are manufactured with the same code and therefore cluster around a particular X,Y position.   The codes are designed to fall on an array.  Codes are visualized on an intensity plot, with the highest X intensity at the right and the highest Y intensity at the top.

Image of code map intensity plot

The array is numbered similar to a standard curve, with the highest concentration being designated 1, the second dilution labeled 2, and so on.   As a result, the code array is labeled as follows.
5th dilution 4th dilution 3rd dilution 2nd dilution Highest X intensity
5,1 4,1 3,1 2,1 1,1 Highest Y intensity
5,2 4,2 3,2 2,2 1,2 2nd dilution
5,3 4,3 3,3 2,3 1,3 3rd dilution

Format of PLX file

The association of clusters with analytes is done by providing a text file with a ".PLX" or ".plx" suffix containing an array position for each analyte in the panel.  The format of the file is a list of comma-separated fields giving the two-digit code of the probe, and the name of the probe.   For the example shown above, the PLX file is as follows.
    "1,1",Granzyme B,30000
    "2,2",IL-1 beta,3333

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