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Demetalation kinetics of natural chlorophylls purified from oxygenic photosynthetic organisms: effect of the formyl groups conjugated directly to the chlorin pi-macrocycle.

Authors
  • Hirai, Yuki
  • Tamiaki, Hitoshi
  • Kashimura, Shigenori
  • Saga, Yoshitaka
Type
Published Article
Journal
Photochemical & Photobiological Sciences
Publisher
The Royal Society of Chemistry
Publication Date
Dec 01, 2009
Volume
8
Issue
12
Pages
1701–1707
Identifiers
DOI: 10.1039/b9pp00018f
PMID: 20024167
Source
Medline
License
Unknown

Abstract

Demetalation kinetics of natural chlorophyll (Chl) d purified from Acaryochloris marina was first studied and compared with those of Chls a and b. The demetalation rate constant of Chl d, which possessed a formyl group at the 3-position, was five-fold smaller than that of Chl a possessing a vinyl group at the same position in aqueous acetone at the proton concentration of 1.2 x 10(-3) M at 25 degrees C. In contrast, the demetalation rate constant of Chl b possessing a formyl group at the 7-position was 26 times smaller than that of Chl a. The activation energy of demetalation reaction of Chl d was larger than that of Chl a, but smaller than that of Chl b. These indicate that the substitution effect of 3-formyl group on the acidic removal of central magnesium in Chls was smaller than that of 7-formyl group.

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