Fractionation of particulate material from maize coleoptile homogenates with polyethylene glycol

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Abstract
Polyethyleneglycol (PEG) has been used to sediment particulate material from maize coleoptile homogenates at low centrifugal forces. The resuspended sediments were used for N-1-naphthylphthalamic acid (NPA)-binding studies. Binding activity was influenced by monovalent cations in the resuspension medium, but even at concentrations of up to 1.2 M NaCl or 0.5 M LiCl or CsCl, half of the binding activity was still recovered. Binding activity was influenced by divalent cations, because it decreased when Ca2+ and Mg2+ ions in the medium were complexed with EDTA. Fractionated sedimentation using increasing concentrations of PEG resulted in two peaks of NPA-binding activity at about 3% and 6% PEG. The 3% peak cintained enzymatic markers for mitochondria and endoplasmatic reticulum while the 6% peak contained NPA-binding activity only. Possible explanations for the bimodal distribution of NPA binding after fractionated PEG precipitation are discussed.