Developments in scientific research follow improvements in apparatus—fluorescent calcium ions have been used to study the cyclic interactions in muscle contraction
In a review article of the use of Calcium imaging in physiology studies, Russell notes that calcium ions are:
“…an ubiquitous intracellular messenger that regulates multiple cellular functions such as secretion, contraction, cellular excitability and gene expression in all organ systems.” (Russell, 1605)
We have encountered them in detail in looking at synapses and muscle contraction in animals and also their role in the formation of the cell wall in plants. Clearly calcium is an important element whose roles range wider than just making healthy bones and teeth!
Advances in technology enable us to collect data that is otherwise outside the the abilities of human perception; this provides the evidence to develop theories. In 1962 it was reported that scientists had extracted a Ca2+-sensitive bioluminescent protein from the jellyfish, Aequoria victoria. and gave it the name “aequorin”. Aequorin emits light when it reacts with calcium and this can be detected experimentally by illumination with different types of radiation. In many cases, a light microscope can be used to view it and it can be photographed or filmed as well.
In topic 11.2 we learn about the role of calcium from the sarcoplasmic reticulum binding to troponin and thus triggering the contractile cycle of actin and myosin. A recent study (Desai et al.) used calcium fluorescence to tag individual molecules of myosin in order to image how single filaments of myosin interact with ATP and Calcium to activate the actin. The team were able to determine that two myosin heads are needed to activate the actin filament and that 11 Myosins bind as part of a regulatory unit.
As technology advances, our understanding of biological processes grows deeper and more complex. This in turn either provides additional evidence in support of existing theories or may suggest alternative explanations. And so science moves on….
Allott, Andrew, and David Mindorff. Biology: Course Companion. Oxford, Oxford University Press, 2014.
Blakely, Sierra. “ Aequorea Victoria .” Aequorea Victoria , Wikipedia, 17 Feb. 2017, en.wikipedia.org/wiki/Aequorea_victoria. Accessed 20 Apr. 2017.
Desai, Rama, Michael A. Geeves, and Neil M. Kad. “Using Fluorescent Myosin to Directly Visualize Cooperative Activation of Thin Filaments.” The Journal of Biological Chemistry 290.4 (2015): 1915–1925. PMC. Web. 20 Apr. 2017.
Russell, James T. “Imaging Calcium Signals in Vivo: a Powerful Tool in Physiology and Pharmacology.” British Journal of Pharmacology, vol. 163, no. 8, 2011, pp. 1605–1625., doi:10.1111/j.1476-5381.2010.00988.x.
Zimmer, Marc. “Green Fluorescent Protein.” Green Fluorescent Protein – The GFP Site, Connecticut College, 18 Aug. 2015, http://www.conncoll.edu/ccacad/zimmer/GFP-ww/GFP-1.htm. Accessed 20 Apr. 2017.