FIG. 1.

Photosensitized labeling of parasites with C₁₆-eosin. (A) Fluorescence microscopy of T. gondii tachyzoites labeled with the photosensitizing lipid analog C₁₆-eosin demonstrates that the C₁₆-eosin is highly concentrated in the parasite pellicle. Bar, 2.5 μm. (B) Autoradiogram of INA-labeled parasite proteins resolved by SDS-PAGE. In the absence of C₁₆-eosin, INA can be activated directly only at wavelengths less than 360 nm. When parasites are labeled with C₁₆-eosin, activation of INA at longer wavelengths results in a subset of proteins being labeled with INA (arrows). D, direct activation; P, photosensitization. Controls for inadvertent direct or indirect activation of INA by ambient light showed that high-intensity irradiation was necessary for significant INA incorporation (LT, samples left uncovered in ambient light; DK, samples wrapped in foil). Numbers on the left indicate molecular mass in kDa.