Assays

Histological stains that have an affinity for specific cellular components have been in use since at least the 1770s when John Hill used carmine to study tissues. Stain variety exploded during the 1800s with German dye manufacturers, such as BASF, developing aniline, methylene blue, and eosin. Eosin is still in use today with hematoxylin for H&E staining.  Since the advent of immunofluorescence and fluorescent protein tagging, which provides very specific labeling, dyes have been relegated to only the most basic imaging. If you don’t need specific proteins labeled, dyes can be a cheap and useful alternative offering simple sample preparation…

The global bacterial biomass has been estimated to be 5x1030, which is significantly higher than plants and animals. We are intimately dependent on bacteria for processing waste, producing vitamin B12, fixing nitrogen and so much more.  While some bacteria are known pathogens, most are not.  These organisms live in all environments from the soil to hot springs to deep thermal vents.  

The most common flow assay is undoubtedly immunophenotyping, in which fluorescently tagged antibodies are used to bind to cellular proteins. This allows you to determine the types of cells present. As long as there is a fluorescent reporter available, it is possible to measure biological processes using flow cytometry – especially in a phenotypically defined manner. Probably the most common of these assays is the calcium flux assay. And that is just the tip of the iceberg. In addition to calcium, it is possible to measure magnesium and zinc concentrations, reactive oxygen species, and even membrane potential using flow. Today,…