Normal Mode Analysis of the Spectral Density of the Fenna鈥揗atthews鈥揙lson Light-Harvesting Protein: How the Protein Dissipates the Excess Energy of Excitons

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• 作者：Thomas Renger ; Alexander Klinger ; Florian Steinecker ; Marcel Schmidt am Busch ; Jorge Numata ; Frank M眉h
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：December 20, 2012
• 年：2012
• 卷：116
• 期：50
• 页码：14565-14580
• 全文大小：774K
• 年卷期：v.116,no.50(December 20, 2012)
• ISSN：1520-5207

文摘

We report a method for the structure-based calculation of the spectral density of the pigment鈥損rotein coupling in light-harvesting complexes that combines normal-mode analysis with the charge density coupling (CDC) and transition charge from electrostatic potential (TrEsp) methods for the computation of site energies and excitonic couplings, respectively. The method is applied to the Fenna鈥揗atthews鈥揙lson (FMO) protein in order to investigate the influence of the different parts of the spectral density as well as correlations among these contributions on the energy transfer dynamics and on the temperature-dependent decay of coherences. The fluctuations and correlations in excitonic couplings as well as the correlations between coupling and site energy fluctuations are found to be 1 order of magnitude smaller in amplitude than the site energy fluctuations. Despite considerable amplitudes of that part of the spectral density which contains correlations in site energy fluctuations, the effect of these correlations on the exciton population dynamics and dephasing of coherences is negligible. The inhomogeneous charge distribution of the protein, which causes variations in local pigment鈥損rotein coupling constants of the normal modes, is responsible for this effect. It is seen thereby that the same building principle that is used by nature to create an excitation energy funnel in the FMO protein also allows for efficient dissipation of the excitons鈥?excess energy.