Optogenetics and Dyes Flashcards
How can ion movement be measured?
using dyes sensitive to the ions
What word is used to describe Ca2+ sensitive dyes?
Chelators
Name 5 low-affinity calcium indicators
- Fura FF
- BTC
- Fura-2
- Fura-5
- Indo-1
what excites the low affinity calcium indicators?
UV light
Name 3 high-affinity calcium indicators
- Fura- 4F
- Fura- 5F
- Fura- 6F
What excites the high affinity calcium indicators?
UV light
Name 3 high affinity and selectivity calcium indicators
- Calcium green
- calcium orange
- oregon green
How are high affinity and selectivity calcium indicators excited and detected?
excited by visible light under scanning laser confocal microscopy
What is Fluorescence?
the phenomenon in which the molecular absorption of a photon triggers the emission of another photon with a longer wavelength
What happens to Fura-2 when Ca2+ binds?
it’s distorted, changing its emission wavelength
How does the fluorescence of Fura-dyes change when there’s a greater concentration of Ca2+?
it gets more fluorescent
Are indicator dyes polar or non-polar?
polar
what’s the issue with indicator dyes being polar?
they can’t diffuse through the membrane to the cytoplasm
what allows indicator dyes to enter the cytoplasm?
the addition of AM Ester, making the molecule polar so it can cross through the membrane
Once the indicator dye is in the cytoplasm, what stops it from leaving?
Esterases in the cytoplasm break-down the ester group, making the molecule polar again (can’t diffuse through the membrane)
Why are ion dyes so important? (2)
- they can show ion fluxes in real time
- they can determine the spatial distribution of ion fluxes
What is Optogenetics?
using light to activate ion channels/ ion pumps
What is channelrhodopsin?
rhodopsin from green algae
where does channelrhodopsin work?
in ion channels
what activates channelrhodopsin?
light with a 480nm wavelength
What is halorhodopsin?
rhodopsin from halobacteria
where does halorhodopsin work?
in chloride pumps
what activates halorhodopsin?
light at 590nm wavelength
what colour light activates channelrhodopsin?
blue- light
