Alkyl and omega-amino alkyl agaroses as probes of light-induced changes in phytochrome from pea seedlings (Pisum sativum cv. Alaska).

Partially purified phytochrome from peas (Pisum sativum cv. Alaska) was absorbed to alkyl and omega-amino alkyl agaroses varying in the number of carbons in their alkyl chains from 2 to 10. The absorption and the elution of the absorbed phytochrome from them with KCl, KI, ethylene glycol and surfactants were investigated either in the dark or under red light in order to detect any chemical differences between the red-light-absorbing form of phytochrome (Pr) and the far-red-light-absorbing form of phytochrome (Pfr). With increasing alkyl chain length, more phytochrome was absorbed to the substituted agaroses. Phytochrome was absorbed to a greater extent by alkyl agaroses than by the less hydrophobic omega-amino alkyl agaroses. Absorbed Pfr was eluted by all the eluants tested to a lesser extent than the absorbed Pr. In those cases in which phytochrome could be eluted by KCl, a higher concentration was required to elute Pfr than Pr. As the chain length of the alkyl groups was increased, the difference in elution of Pr and Pfr by KCl increased. Phytochrome was salted out at a lesser concentration of ammonium sulfate after brief red-light irradiation than in the dark. Absorption of phytochrome to DEAE-agarose was also investigated as an example of ionic phytochrome-ligand interactions. The difference between the affinity of Pr and Pfr for DEAE-agarose was less than it was for omega-amino alkyl or alkyl agarose. It is concluded that Pfr is more hydrophobic than Pr.