Figure 3.

Growing order for pSILAC spheroids demonstrating the radial locations of the isotopic labels. Spheroids are grown for 12 days. The top (a) figure represents the spheroids used for duplex label specificity. Spheroids with a single heavy layer were prepared (top row) and control spheroids that were only grown in either light or heavy media. Light media (L) are green and heavy media (H) are red. The bottom (b) shows the triplex spheroids used to examine varying permutations. Each spheroid is grown with variations of three isotopic media, light (green), medium (blue), and heavy (red) for 4 days. The arrows represent growth time, and the colors indicate the presence of the isotopic labels. The labeling convention is core middle outer with respect to isotopic labels.¹⁹