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Excitable Cells - Lecture 12 (08/03/2018)
Optogenetics and Dyes
Non-Invasive Methods to Record and Control Neuronal Activity
Activity reporters of neurones are used to record their activity, particularly calcium.
Optogenetics can be used to control the activity by using light to alter neuron activity.
Electrodes are good for studying single cells, but not a large group of cells.
Chemists realised calcium could be used to alter the activity of a molecule.
Neurologists can measure this change in Ca 2+ concentration using Ca2+ sensitive dyes.
The more calcium present, the more electric impulses have been received.
Calcium fluorescent dyes are Chelators and there are many different types of them.
The type of dye chosen to use depends on the cell type you are investigating, and whether you require a high affinity or just a low affinity calcium indicator.
Chelators are molecules which bind to calcium.
These chelator dyes are either excited by UV or visible light so they can be identified.
Florescence is the phenomenon in which the molecular absorption of a photon triggers the emission of another photon with a longer wavelength.
Florescence is named after the first identified fluorescent molecule calcium fluoride "Fluorite".
For example, if the molecule is stimulated in the ultraviolet range, then the emitted light is released in the visible range.
Hence it is possible to identify locations through the use of fluorescent tagging.
It can also be used to observe the activity of neurones.
Fura-2 an example of an ion sensitive dye
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