Calcium imaging
Calcium imaging refers to the use of calcium ion indicator to monitor calcium ion concentration in cell, tissue or media. This technique is widely used to study calcium signalling in neuronal activity in vivo and in vitro.
There are two widely used calcium indicators: chemical indicators and generic-encoded indicators (GECIs).
Chemical indicators
Chemical indicators are small molecules that can chelate calcium ions. All these molecules are based on an EGTA homologue called BAPTA, with high selectivity for calcium (Ca2+) ions versus magnesium (Mg2+) ions. The commonly used chemical indicators are Oregon Green-1, Fura-2, Indo-1, Fluo-3 and Fluo-4.
Genetically encoded calcium indicator (GECIs)
GECIs are fluorescent proteins derived from green fluorescent protein (GFP) or its variants fused with calmodulin (CaM) and the M13. These proteins can be easily transfected to cells and enable non-invasive measurement in vivo, so this techniques are widely used for imaging neural activity,T-cell,etc. The common used GECIs are in the list below.
GCaMP variants
|
Variant |
Description |
|
GCaMP6S |
Ultrasensitive GCaMP variant; slow kinetics |
|
GCaMP6m |
Ultrasensitive GCaMP variant; medium kinetics |
|
GCaMP6f |
Ultrasensitive GCaMP variant; fast kinetics |
|
GCaMPARI |
Efficient and irreversible green-to-red conversion upon elevated calcium concentration and simultaneous illumination |
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References
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3. Tallini YN, Ohkura M, Choi BR, Ji G, Imoto K, Doran R, Lee J, Plan P, Wilson J, Xin HB, Sanbe A, Gulick J, Mathai J, Robbins J, Salama G, Nakai J, Kotlikoff MI (March 2006). "Imaging cellular signals in the heart in vivo: Cardiac expression of the high-signal Ca2+ indicator GCaMP2". Proceedings of the National Academy of Sciences of the United States of America. 103 (12): 4753–8.
