To know how many proteins assemble together at the nanoscale is fundamental for understanding protein function. Sometimes, proteins must be in an "oligomeric" state to be functional, although "oligomerization" of certain proteins can also lead to diseases. The ability to determine protein stoichiometry and monitor changes in the balance between monomeric, dimeric and multi-meric proteins can allow scientists to see the differences between a properly functioning cell and a diseased cell. Therefore, there is a great interest in being able to count proteins and determine their stoichiometry.
In a recent study carried out at ICFO, the Institute of Photonic Sciences, the research group of Advanced fluorescence imaging and biophysics, led by Nest Fellow Dr. Melike Lakadamyali was able to quantify the photoactivation efficiency of all the known "ir-reversibly photoswitching fluorescent proteins" and establish a proper detailed reference framework for determining protein stoichiometry. To do this, they used a nanotemplate of known stoichiometry (the human Glycine receptor expressed in Xenopus oocytes) and studied several fluorescent proteins to see the percentage of proteins that was photoactivated. The results of this study have recently been published in Nature Methods.
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