Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

DICHOTOMOUS DISORDER MODEL FOR SINGLE LIGHT-HARVESTING COMPLEXES
Danielis Rutkauskas
Institute of Physics, Center for Physical Sciences and Technology, Savanorių 231, 02300 Vilnius, Lithuania
E-mail: danielis@ar.fi.lt
Received 5 November 2018; accepted 2 January 2019

Photosynthetic organisms conserve the captured energy of solar radiation into stable chemical forms. To do so, they have evolved specialized systems of pigment–protein complexes consisting of light-harvesting antennas and reaction centres. Photosynthetic antennas contain remarkably dense arrangements of light-absorbing pigments held by the protein scaffold, and their function is to absorb light and funnel the excitation energy to the reaction centre. Decades of experimental and theoretical research resulted in a detailed understanding of the energy migration pathways within the photosynthetic apparatus. The key parameters determining the excitation relaxation and transfer are inter-pigment coupling and energetic disorder or non-equality of excitation energies at equivalent pigment sites due to the interaction with the disordered protein scaffold. Circularly symmetric light-harvesting antennas from purple bacteria present a beautiful example of the interplay between these parameters. The spectral signature of this interplay could be observed with the single-molecule fluorescence microscopy techniques. The results of these measurements were interpreted with an intuitively clear dichotomous model of disorder of pigment site energies.

Keywords: photosynthetic, light-harvesting, antenna, energetic disorder, single-molecule
PACS: 87.64.kv, 71.35.Aa, 87.80.Nj

DICHOTOMINIS NETVARKOS MODELIS PAVIENIAMS ŠVIESĄ SUGERIANTIEMS KOMPLEKSAMS
Danielis Rutkauskas

Fizinių ir technologijos mokslų centro Fizikos institutas, Vilnius, Lithuania

Fotosintetiniai organizmai transformuoja ir išsaugo sugertą saulės šviesos energiją stabilios cheminės energijos pavidalu. Tam padaryti evoliucijos metu jie išvystė specializuotas pigmentų-baltymų kompleksų sistemas, sudarytas iš šviesą sugeriančių antenų ir reakcijos centrų. Fotosintetinės antenos sudarytos iš tankaus pigmentų tinklo, laikomo baltymo karkaso, o jų funkcija yra sugerti šviesą ir nukreipti sužadinimo energiją į reakcijos centrą. Dešimtmečiai eksperimentinio ir teorinio darbo leido atskleisti detalų energijos pernašos paveikslą fotosintetiniame aparate. Pagrindiniai parametrai, lemiantys sužadinimo energijos relaksaciją ir pernašą, yra tarppigmentinės sąveikos stiprumas ir energetinė netvarka arba pigmentų, esančių ekvivalentiškose padėtyse, sužadinimo energijos netapatumas dėl sąveikos su netvarkia baltymo matrica. Cilindriškai simetriškos šviesą sugeriančios antenos iš purpurinių bakterijų yra geras šių parametrų sąveiką iliustruojantis pavyzdys. Spektrinė šios sąveikos reprezentacija buvo aiškiai stebima naudojant pavienių molekulių fluorescencijos mikroskopiją. Šių matavimų rezultatai buvo interpretuoti naudojant intuityviai lengvai suprantamą dichotominį energetinės netvarkos modelį.

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