title: Excited-State Properties of Protochlorophyllide Analogues and Implications for Light-Driven Synthesis of Chlorophyll.
abstract: Protochlorophyllide (Pchlide), an intermediate in the biosynthesis of chlorophyll, is the substrate for the light-driven enzyme protochlorophyllide oxidoreductase. Pchlide has excited-state properties that allow it to initiate photochemistry in the enzyme active site, which involves reduction of Pchlide by sequential hydride and proton transfer. The basis of this photochemical behavior has been investigated here using a combination of time-resolved spectroscopies and density functional theory 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 important for harnessing light energy.
authors.affiliation: Manchester Institute of Biotechnology and School of Chemistry, The University of Manchester , 131 Princess Street, Manchester M1 7DN, U.K.
authors.forename: Derren J
authors.initials: DJ
authors.lastname: Heyes
authors.affiliation: Manchester Institute of Biotechnology and School of Chemistry, The University of Manchester , 131 Princess Street, Manchester M1 7DN, U.K.
authors.forename: Samantha J O
authors.initials: SJ
authors.lastname: Hardman
authors.affiliation: Manchester Institute of Biotechnology and School of Chemistry, The University of Manchester , 131 Princess Street, Manchester M1 7DN, U.K.
authors.forename: David
authors.initials: D
authors.lastname: Mansell
authors.affiliation: Manchester Institute of Biotechnology and School of Chemistry, The University of Manchester , 131 Princess Street, Manchester M1 7DN, U.K.
authors.forename: Aisling
authors.initials: A
authors.lastname: Ní Cheallaigh
authors.affiliation: Manchester Institute of Biotechnology and School of Chemistry, The University of Manchester , 131 Princess Street, Manchester M1 7DN, U.K.
authors.forename: John M
authors.initials: JM
authors.lastname: Gardiner
authors.affiliation: Manchester Institute of Biotechnology and School of Chemistry, The University of Manchester , 131 Princess Street, Manchester M1 7DN, U.K.
authors.forename: Linus O
authors.initials: LO
authors.lastname: Johannissen
authors.affiliation: Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council , Harwell Oxford, Didcot OX11 0QX, U.K.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Greetham
authors.affiliation: Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council , Harwell Oxford, Didcot OX11 0QX, U.K.
authors.forename: Michael
authors.initials: M
authors.lastname: Towrie
authors.affiliation: Manchester Institute of Biotechnology and School of Chemistry, The University of Manchester , 131 Princess Street, Manchester M1 7DN, U.K.
authors.forename: Nigel S
authors.initials: NS
authors.lastname: Scrutton
mesh_terms: D002734:Chlorophyll / Q000138:chemical synthesis* / Q000737:chemistry; D008027:Light; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011521:Protochlorophyllide / Q000031:analogs & derivatives / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D009942:Organometallic Compounds; D002734:Chlorophyll; D011521:Protochlorophyllide