How does Fluorescence-activated cell sorting (FACS) work?


FACS in biomedical research methods. How does this really work and why and for what? If you add a charge on a molecule, won’t that change the physiological and chemical structure and won’t that defeat the purpose of sorting and isolating the cell. I feel like i’m misunderstanding something, can someone please explain like i’m 5

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The basic idea is fairly simple. You first apply a label to your cells, often with fluorophore-conjugated monoclonal antibodies. Then the FACS device passes the cells by a laser of a particular wavelength which excites the fluorophore and causes it to emit a different wavelength that is captured by detectors. If you’re performing sorting on your cells, that detector readout can also be used to immediately divert them into different wells of a microplate, etc.

I’m not 100% sure what you mean with the charge thing; of course it’s true that altering a molecule’s charge changes its properties, but you’ll need to be more specific about what exactly you’re altering. Though, when you’re using FACS/flow cytometry for sorting, it *is* important to consider that sticking a bunch of antibodies on particular molecules on those cells may bring about unwanted changes. For instance, sorting T cells by labeling their CD3/CD28 will definitely mess with future experiments. That’s why it’s often preferable to do negative selection, where you label and sort out everything *not* of interest.