Excited State Properties of Protochlorophyllide Analogues and Implications for Light Driven Synthesis of Chlorophyll

Research output: Contribution to journalArticle

  • External authors:
  • Derren Heyes
  • David Mansell
  • Aisling Ni Cheallaigh
  • John Gardiner
  • Linus Johannissen
  • Gregory M. Greetham
  • Michael Towrie

Abstract

Protochlorophyllide (Pchlide), an intermediate in the biosynthesis of chlorophyll, is the substrate for the light-driven enzyme protochlorophyllide oxidoreductase (POR). Pchlide has excited state properties that allow it to initiate photochemistry in the enzyme active site that involves reduction of Pchlide by sequential hydride and proton transfer. The basis of this photochemical behavior is investigated here using a combination of time-resolved spectroscopies and DFT calculations of a number of Pchlide analogues with modifications to various substituent groups. A keto group on ring E is essential for excited state charge separation in the molecule, which is the driving force for the photoreactivity of the pigment. Vibrational “fingerprints” of specific regions of the Pchlide chromophore have been assigned, allowing identification of the modes that are crucial for excited state chemistry in the enzyme. This work provides an understanding of the structural determinants of Pchlide that are so important for harnessing light energy.

Bibliographical metadata

Original languageEnglish
JournalThe Journal of Physical Chemistry Part B
Early online date24 Jan 2017
StatePublished - 2017