References:

• Nagai T, Sawano A, Park ES, Miyawaki A. Circularly permuted green fluorescent proteins engineered to sense Ca²⁺. Proc Natl Acad Sci U S A. 2001; 98 (6):3197-202. / pmid: 11248055
• Nakai J, Ohkura M, Imoto K. A high signal-to-noise Ca(2+) probe composed of a single green fluorescent protein. Nat Biotechnol. 2001; 19 (2):137-41. / pmid: 11175727
• Souslova EA, Belousov VV, Lock J, Stromblad S, Kasparov S, Bolshakov AP, Pinelis VG, Labas YA, Lukyanov S, Mayr LM, Chudakov DM. Single fluorescent protein-based Ca²⁺ sensors with increased dynamic range. BMC Biotechnol. 2007; 7 :37. / pmid: 17603870