Structure and Conformation of Photosynthetic Pigments and Related Compounds. 13. Identification of Localized Vibrational Modes in Chlorophyll A Derivatives

Abstract

A Resonance Raman investigation of chlorophyll a and meso-chlorinated and ring V hydroxylated derivatives and pheophytins reveals localized vibrational modes in the chlorophyll series. Both chlorination and hydroxylation give rise to changes in both band intensity and frequency throughout the spectrum. Chlorination affects mainly the core sensitive bands with C a C m and C a N character. Hydroxylation leads to changes in the carbonyl and ring V associated bands. Small, but real spectral differences were found between the 10-epimers.

61 The Structural Chemistry of Isolated Chlorophylls

“…66 Resonance Raman and other vibrational techniques have been used to investigate this situation and have provided supporting information for structural flexibility of the chromophores. 67,68,69,70 This has been reviewed before 35 and an update will be given elsewhere. 71 RR spectral changes have been observed in PSI after exposure to high light intensities, indicating the extent of photodamage to the Chl a pigments and providing insight into the mechanisms of photoprotection.…”