FIGURE 2.
Shown is the variation of the 31P R1 of PMe (A) or PC (B) with field for mixed vesicles of PC/PMe (5:5 mm) in the presence of 14.4 μm PI-PLC spin-labeled on the cysteine: W47C (□), D205C (●), and N220C (+). C, field dependence of the additional PC R1 component due to spin-labeled D205C protein (ΔR1). The globally optimized fit (solid line) is consistent with τP-e = 2 μs; ΔRP-e(0), the other key parameter for determining the P-e distance is indicated. If one refits the data in C to Equation 1 with a τP-e of 1 μs (shown as a dotted line), the ΔRP-e(0) is about half of that obtained from using 2 μs; hence, the τP-e/ΔRP-e(0) is about the same, leading to the same distance estimate. Error bars in C are from the least squares fit used to determine R1 at each field.