What does a voltage pulse indicate when a cell passes the laser beam?

When a cell passes through a laser beam in a flow cytometer, a voltage pulse is generated that primarily provides information about the size and structure of the cell. This voltage pulse corresponds to the amount of light scattered by the cell as it interrupts the laser beam. Generally, larger cells will scatter more light and produce a stronger signal, resulting in a higher voltage pulse, while smaller cells will generate a lower voltage pulse.

The size of the cell can be inferred from the amplitude of this voltage pulse, while differences in cell structure, such as granularity or internal complexity, can also influence the scattering pattern and therefore alter the voltage signal. This is critical for distinguishing different types of cells in a sample, as variations in size and structure are often key indicators used in cytometry to identify and analyze populations of cells.

While other aspects of cellular characteristics may be informative in cytometry, such as identifying contaminants or analyzing fluorophore properties, the primary utility of the voltage pulse in this context is related to the size and structural information of the cells as they flow past the laser.