Figure 4

The interactions between Big domains and Ca²⁺.

(A) CD spectrum of SP0498 Big domain mixed with Stains-all dye at molar ratio of 10:1. (B) Titration of SP0498 Big domain with Ca²⁺, measured by ITC in 20 mM HEPES buffer (containing 100 mM NaCl) at pH 6.5 and 20°C. The upper thermogram panel shows the observed heats for each injection of CaCl₂ at 120 s intervals after baseline correction, whereas the lower panel depicts the binding enthalpies vs. Ca²⁺/protein molar ratio. (C) Titration of Lig A3 (the third Big domain of Lig A with the accession number of FJ030917) with Ca²⁺, measured by ITC in 20 mM HEPES buffer (containing 100 mM NaCl) at pH 6.5 and 20°C. The upper thermogram panel shows the observed heats for each injection of CaCl₂ at 120 s intervals after baseline correction whereas the lower panel depicts the binding enthalpies vs. Ca²⁺/protein molar ratio.