Aggregation of chlorophyll a probed by resonance light scattering spectroscopy

We report the resonance light scattering (RLS) spectra of chlorophyll a aggregated in a 9:1 solution of formamide and pH 6.8 phosphate buffer. The aggregate formed after 2 h of mixing, referred to as Chl469, shows a strong scattering feature at 469 nm (Soret band) and a much weaker feature at 699 nm...

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Bibliographic Details
Published in:Biophysical journal 1995, Vol.68 (1), p.335-341
Main Authors: de Paula, J.C., Robblee, J.H., Pasternack, R.F.
Format: Article
Language:English
Subjects:
Biophysical Phenomena
Biophysics
Chlorophyll - chemistry
chlorophylle
chlorophylls
Circular Dichroism
clorofilas
espectrometria
Formamides
Hydrogen-Ion Concentration
Kinetics
Light
Molecular Conformation
Scattering, Radiation
Sensitivity and Specificity
Solutions
spectrometrie
spectrometry
Spectrophotometry - methods
Spectrophotometry - statistics & numerical data
spinacia oleracea
Water
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Description
Summary:We report the resonance light scattering (RLS) spectra of chlorophyll a aggregated in a 9:1 solution of formamide and pH 6.8 phosphate buffer. The aggregate formed after 2 h of mixing, referred to as Chl469, shows a strong scattering feature at 469 nm (Soret band) and a much weaker feature at 699 nm (Qy band). A kinetic investigation confirmed that the aggregation process is cooperative, and also detected one intermediate (Chl458) with a strong RLS spectrum but only a weak CD spectrum. We propose that aggregation proceeds via at least three steps: 1) formation of a nucleating species, probably a dimer of chlorophylls; 2) formation of large aggregates with little or no secondary structure (e.g., Chl458); and 3) conformational change to form helical aggregate (Chl469).
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(95)80192-X