FIGURE 8.

Detailed identification of complexes of NeuTTM (10 μm) in binary and ternary mixtures with MgCl₂ (0. 1 mm) and/or PPP_i (25 μm). The spectra were all recorded in 100 mm ammonium acetate, pH 6.5, at an RF lens 1 voltage = 150 V for a more accurate mass determination of each complex. A, NeuTTM alone at charge state 8+ is shown. The main peak corresponds to the uptake of eight protons, and few sodium or potassium adducts are detected. B, NeuTTM binary mixture with Mg²⁺ is shown. The intensity of unresolved adducts peaks increases, but the fully protonated protein remains the most intense peak. C, shown is a NeuTTM binary mixture with PPP_i. The fully protonated complex is minor, and the major complexes take up two monovalent cations. D, shown is a NeuTTM ternary mixture with PPP_i and Mg²⁺. The enzyme-substrate complex with the uptake of one Mg²⁺ is clearly detected. M, monomer; M₂, dimer.