Fig. 4.

Total ion and selected ion images (positive mode ToF-SIMS) of the animal hemisphere of X. laevis zygote 10 min postinsemination. Spectral dose density is 5 × 10¹³ ions/cm² using a 4 μm-focused 40 keV C₆₀⁺ beam over 1,200 × 1,200 μm² with 256 × 256 pixels. The surface region marked with a white circle is the proposed egg-sperm fusion site. The m/z 165.1 is a common glycerophospholipid fragment; m/z 166.1 and 184.1, the fragments from GPCho and SM; m/z 224.1, the fragment from GPCho; m/z 265.2, the characteristic peak of SM; m/z 313.3, MAG [C₁₉H₃₇O₃]⁺ C16:0; m/z 369.4, cholesterol fragment; m/z 577.5, DAG [C₃₇H₆₉O₄]⁺ C34:1; m/z 152.1, 189.1 and 202.1 are unassigned ions. The color scale corresponds to the relative ion intensity and the maximum count (mc) per pixel is displayed in each image frame. Adapted from (25).