
This morning, someone asked me about the separation and characterization of alleged viruses—or particles in general. I shared the following response, which I believe may also be useful to others. (The original query is attached below.)
Let me explain, as there seems to be some misunderstanding. SDS-PAGE is a separation technique, essentially a sorting tool. [Edited: In general, SDS-PAGE separation refers to the use of Sodium Dodecyl Sulfate (SDS) in combination with polyacrylamide gel electrophoresis (PAGE)]. The application of a reference standard (or calibration) to an SDS-PAGE plate will indicate where the particles of interest are expected to migrate or be observed. Once the SDS-PAGE run is completed, we see a band at that location. However, from a professional and scientific perspective, the work is not finished at this point. The band we see may or may not correspond to the actual particles of interest—it could be slightly different, or even completely unrelated particles, but of the same size. This is because SDS-PAGE only separates particles based on their size; it does not identify them. For this reason, SDS-PAGE is classified as a separation technique, not a characterization technique. In this context, SDS-PAGE can be viewed as a more efficient alternative to ultracentrifugation, another separation technique that offers significantly lower resolution compared to SDS-PAGE.
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