FIGURE 5.

Dependence of the paramagnetic enhancement of ³¹P R₁ for PA/PC (1:1) vesicles caused by the presence of 0.5 mg/ml spin-labeled C148S (open symbols) or spin-labeled C188S (filled symbols). The vesicles contained 10 mm each of PA (● and ○) and PC (■ and □). Note that for this amount of protein and phospholipid, the spin label on Cys-188 (i.e. labeled C148S) has virtually no effect at low field for either phospholipid, although the spin label attached to Cys-148 (labeled C188S) has a larger enhancement. The error bars represent the error in the fit to obtain R₁ for each field strength.