Fig. 4.

Hyperpolarized ¹²⁹Xe NMR spectra of biosensor 5 alone, binding α_IIbβ₃ integrin, and blocked by c[RGDyK], all studies in Tris buffer (1 mM, pH 7.2) (a) 5 gave ¹²⁹Xe NMR chemical shift at 65.8 ppm. (b) 5 and α_IIbβ₃ integrin in Tris buffer with 30% glycerol and 0.1% Triton X-100. “Free” biosensor gave ¹²⁹Xe NMR chemical shift at 67.1 ppm, which was shifted 1.3 ppm downfield from “free” biosensor in (a) due to addition of glycerol. “Bound” biosensor appeared at 71.2 ppm, representing a 4.1 ppm downfield shift. (c) c[RGDyK] added to solution of 5 and α_IIbβ₃ integrin gave “free” biosensor at the same ¹²⁹Xe NMR chemical shift, but no “bound” biosensor was detected.