Figure 3.

(a) Overlay of ¹H,¹⁵N HSQC spectra of 1 mM holo CaM (red, 500 μM Ca²⁺) and NP-bound CaM (blue, 500 μM Ca²⁺, 1.4 mg/mL CaF₂ NP). Residues within the four EF-hands are highlighted. Down-field shifts of the amide protons of G25, G61, G98 and G134 are indicative of Ca²⁺ complexation. Mainly residues close to the N-terminal and not the C-terminal EF-hands experience CSP upon addition of CaF₂ nanoparticles. (b) Close-up of residues which coordinate Ca²⁺ in the N-terminal EF-hand motifs (EF1 and EF2). (c) Signal attenuation upon addition of NPs. The ratio of intensity in the presence (I_NP) and absence (I₀) of nanoparticles is plotted against the sequence of Calmodulin.