Principal component analysis (PCA) of 2D-DIGE data. This figure depicts a principal component analysis in which principal components (PC) 1 and 2 are plotted for all 454 matched protein spots. PC1 accounted for 42.54% of the variance and PC2 accounted for 12.76% and segregated the groups by ozone exposure and SP-A deletion, respectively. Circles represent the WT mice and triangles represent KO mice. The open symbols represent samples that were exposed to FA and the black symbols represent those exposed to ozone.