Chlorophyll ring deformation modulates Qy electronic energy in chlorophyll-protein complexes and generates spectral forms
Articolo
Data di Pubblicazione:
2007
Citazione:
Chlorophyll ring deformation modulates Qy electronic energy in chlorophyll-protein complexes and generates spectral forms / G. Zucchelli, D. Brogioli, A.P. Casazza, F.M. Garlaschi, R.C. Jennings. - In: BIOPHYSICAL JOURNAL. - ISSN 0006-3495. - 93:6(2007 Sep), pp. 2240-2254.
Abstract:
The possibility that the chlorophyll (chl) ring distortions observed in the crystal structures of chl-protein complexes
are involved in the transition energy modulation, giving rise to the spectral forms, is investigated. The out-of-plane chl-macrocycle
distortions are described using an orthonormal set of deformations, defined by the displacements along the six lowest-frequency,
out-of-plane normal coordinates. The total chl-ring deformation is the linear combination of these six deformations. The two higher
occupied and the two lower unoccupied chl molecular orbitals, which define the Qy electronic transition, have the same symmetry
as four of the six out-of-plane lowest frequency modes. We assume that a deformation along the normal-coordinate having the
same symmetry as a given molecular orbital will perturb that orbital and modify its energy. The changes in the chl Qy transition
energies are evaluated in the Peridinin-Chl-Protein complex and in light harvesting complex II (LHCII), using crystallographic data.
The macrocycle deformations induce a distribution of the chl Qy electronic energy transitions which, for LHCII, is broader for chla
than for chlb. This provides the physical mechanism to explain the long-held view that the chla spectral forms in LHCII are both more
numerous and cover a wider energy range than those of chlb.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
G. Zucchelli, D. Brogioli, A.P. Casazza, F.M. Garlaschi, R.C. Jennings
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