Fig. 3: Raman spectroscopic imaging reveals spatial compartmentalization of fumarate.

A Fumarate concentrations in Fh1-WT cells (n = 20, black) and Fh1-KO cells (n = 20, purple: cl.1, pink: cl.19), normalised by the number of pixels per area scan (bin width: 5 mM). Histograms are presented as mean values ± SD. B, C K-means clustering loadings extracted from the combined analysis of (B) 20 Fh1-WT cells and (C) 20 Fh1-KO cl.19 cells. Loadings are assigned to substrate (grey), nucleus (yellow),membrane (blue), and mitochondria (green). For Fh1-KO cells, two classes are assigned to the mitochondria. D Exemplar fumarate concentration maps (left) and k-means clustering maps (right) for two Fh1-WT cells. The labelling of the k-means cluster maps corresponds in colour to the loadings in (B, C). E As (D) but for two Fh1-KO cl.19 cells. F–H Fumarate concentrations plotted per cluster class for (F) the 20 Fh1-WT cells from (A, B), (G) the 20 Fh1-KO cells cl. 1 cells from (A), and (H) the 20 Fh1-KO cells cl. 19 cells from (A,C). Values are tabulated in Table 1. The box plot indicates the median value with 95% confidence interval (sloped edges), 1st/3rd quartile (box edges), and 9th/91st percentile whiskers. The pink dot indicates the mean fumarate concentration in the cluster class. The grey-shaded area marks concentrations below the estimated LOD. Source data are provided as a Source Data file.