Unraveling the Intrinsic Color of Chlorophyll

Bruce F. Milne, Yoni Toker, Angel Rubio, Steen Brøndsted Nielsen

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50 Citations (Scopus)


The exact color of light absorbed by chlorophyll (Chl) pigments, the light-harvesters in photosynthesis, is tuned by the protein microenvironment, but without knowledge of the intrinsic color of Chl it remains unclear how large this effect is. Experimental first absorption energies of Chl a and b isolated in vacuo and tagged with quaternary ammonium cations are reported. The energies are largely insensitive to details of the tag structure, a finding supported by first-principles calculations using time-dependent density functional theory. Absorption is significantly blue-shifted compared to that of Chl-containing proteins (by 30–70 nm). A single red-shifting perturbation, such as axial ligation or the protein medium, is insufficient to account even for the smallest shift; the largest requires pigment–pigment interactions.
Original languageEnglish
Pages (from-to)2170-2173
Number of pages4
JournalAngewandte Chemie International Edition
Issue number7
Publication statusPublished - 30 Dec 2015

Bibliographical note

B.F.M. thanks DIPC and CFM (UPV/EHU) and the Laboratory for Advanced Computation (University of Coimbra) for support. S.B.N. acknowledges support from Lundbeckfonden. A.R. acknowledges support from ERC Advanced Grant DYNamo (ERC-2010-AdG-267374), Spanish Grant (FIS2013-46159-C3-1-P), Grupos Consolidados UPV/EHU del Gobierno Vasco (IT578-13), and EC FP7 CRONOS (Grant 280879-2).


  • action spectroscopy
  • chlorophyll
  • color tuning
  • photosynthesis
  • time-dependent density functional theory


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