2.3. Protein extraction and quantification
The method was similar to that of Olley et al. (1996). Individual
petals and columns were separately ground in liquid nitrogen and
mixed with 5mL of buffer containing 50mmolL.1 Tris.HCl, pH 7.6,
2mmolL.1 disodium ethylenediamine tetraacetate, 2mmolL.1
dithiothreitol and 10mmolL.1 MgCl2, for 30 min at 25 .C. The
homogenates were centrifuged at 17,000~g for 20min at 4 .C. The
supernatant was retained and used as a source of soluble proteins.
Insoluble proteinswere extracted by resuspending the pellets
in 7mL of 0.1 mol L.1 NaOH and incubating at 80 .C overnight.
The protein contents were measured using the standard Bradford
method and bovine serum albumin.