Copper responsive protein expression: the relationship between normalised spot quantity and liver copper. All 2-D gels in the study (3 replicates per animal) were assembled into one PDQuest matchset. Normalised protein spot quantities (in units of optical density ± SEM) for individual animals, both control and copper supplemented, are plotted against liver copper (μg/g, mean value of dorsal and ventral lobes). Symbols: Black and white triangles represent NR and Cambridge values respectively. Trend lines have been added manually to aid interpretation.