Table 1.

Marker enzyme assays illustrating the presence of cytoplasmic and plasma membrane contamination in the various stages of the purification of barley root mitochondria and mitoplasts

Fraction	Cytoplasm marker: NR specific activity, nmol NO per mg protein per h	Plasma membrane marker: P-type ATPase specific activity, μmol Pi per mg protein per h	Mitochondrial marker: F-type ATPase specific activity, μmol Pi per mg protein−1 per min
Whole homogenate of barley roots	155  ± 14	3.0  ± 0.4	0.03  ± 0.002
Supernatant post 1,000 × g spin	134  ± 18	2.9  ± 0.5	0.05  ± 0.002
Pellet post 9,000 × g spin	12  ± 3	1.1  ± 0.02	3.4  ± 0.5
Pellet post Percoll gradient	0	0.5  ± 0.01	3.6  ± 0.6
Mitochondria after three washings	0	0	4.1  ± 0.4
Mitoplasts	0	0	5.6  ± 0.7

Data presented are for three independent isolation and purification experiments with values for the various enzyme activities and their standard errors.