Time-Resolved Circular Dichroism of Native Oat Phytochrome Photointermediates

Sofie C. Björling, Chian Fan Zhang, David L. Farrens, Pill Soon Song, David S. Kliger

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Time-resolved circular dichroism (TRCD) spectral studies of the Pr→ Pfr phototransformation in native oat phytochrome (124 kDa) were performed in the 500-800 nm spectral region from 500 ns to 500 ms after photolysis at 10 °C. The first intermediate observed in our measurements, lumi-R, had an absorption maximum at 695 nm, but its difference TRCD spectrum showed a CD maximum near 660 nm. This result differed from results of previous steady-state CD measurements where the intermediates of the photoconversion were trapped at low temperatures. Possible explanations for the discrepancies in the TRCD results vs low-temperature CD results are discussed. We conclude that the first species trapped in the low-temperature CD experiment is most probably an unrelaxed lumi-R-type intermediate. The subsequent species probed during the Pr → Pfr phototransformation have similar CD spectra. The structural implications of the TRCD results are discussed.

Original languageEnglish (US)
Pages (from-to)4581-4588
Number of pages8
JournalJournal of the American Chemical Society
Issue number12
StatePublished - Jun 1 1992
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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