@article {6892,
	title = {Optimized ratiometric calcium sensors for functional in vivo imaging of neurons and T lymphocytes.},
	journal = {Nature Methods},
	volume = {11},
	year = {2014},
	month = {2014 Feb},
	pages = {175-82},
	abstract = {<p>The quality of genetically encoded calcium indicators (GECIs) has improved dramatically in recent years, but high-performing ratiometric indicators are still rare. Here we describe a series of fluorescence resonance energy transfer (FRET)-based calcium biosensors with a reduced number of calcium binding sites per sensor. These {\textquoteright}Twitch{\textquoteright} sensors are based on the C-terminal domain of Opsanus troponin C. Their FRET responses were optimized by a large-scale functional screen in bacterial colonies, refined by a secondary screen in rat hippocampal neuron cultures. We tested the in vivo performance of the most sensitive variants in the brain and lymph nodes of mice. The sensitivity of the Twitch sensors matched that of synthetic calcium dyes and allowed visualization of tonic action potential firing in neurons and high resolution functional tracking of T lymphocytes. Given their ratiometric readout, their brightness, large dynamic range and linear response properties, Twitch sensors represent versatile tools for neuroscience and immunology.</p>
},
	issn = {1548-7105},
	doi = {10.1038/nmeth.2773},
	author = {Thestrup, Thomas and Litzlbauer, Julia and Bartholom{\"a}us, Ingo and Mues, Marsilius and Russo, Luigi and Dana, Hod and Kovalchuk, Yuri and Liang, Yajie and Kalamakis, Georgios and Laukat, Yvonne and Becker, Stefan and Witte, Gregor and Geiger, Anselm and Allen, Taylor and Rome, Lawrence C and Chen, Tsai-Wen and Kim, Douglas S. and Garaschuk, Olga and Griesinger, Christian and Griesbeck, Oliver}
}
@article {4376,
	title = {Genetically encoded neural activity indicators.},
	journal = {Current Opinion in Neurobiology},
	volume = {22},
	year = {2012},
	month = {2012 Feb},
	pages = {18-23},
	abstract = {<p>Recording activity from identified populations of neurons is a central goal of neuroscience. Changes in membrane depolarization, particularly action potentials, are the most important features of neural physiology to extract, although ions, neurotransmitters, neuromodulators, second messengers, and the activation state of specific proteins are also crucial. Modern fluorescence microscopy provides the basis for such activity mapping, through multi-photon imaging and other optical schemes. Probes remain the rate-limiting step for progress in this field: they should be bright and photostable, and ideally come in multiple colors. Only protein-based reagents permit chronic imaging from genetically specified cells. Here we review recent progress in the design, optimization and deployment of genetically encoded indicators for calcium ions (a proxy for action potentials), membrane potential, and neurotransmitters. We highlight seminal experiments, and present an outlook for future progress.</p>
},
	issn = {1873-6882},
	doi = {10.1016/j.conb.2011.10.024},
	author = {Looger, Loren L and Griesbeck, Oliver}
}
