4IK3:
reference: Structural insight into enhanced calcium indicator GCaMP3 and GCaMPJ to promote further improvement., Chen Y, Song X, Ye S, Miao L, Zhu Y, Zhang RG, Ji G, Protein Cell. 2013 Apr;4(4):299-309. doi: 10.1007/s13238-013-2103-4. Epub 2013, Apr 3. PMID: 23549615

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