Decay- and evolution-associated spectra of time-resolved fluorescence of LHCII aggregates

Abstract

Non-photochemical quenching (NPQ) is responsible for the protection of the photosynthetic apparatus of plants from photodamage at high-light conditions. It is commonly agreed that NPQ takes place in the major light-harvesting complexes (LHCII), however, its exact mechanisms are still under debate. Valuable information about its molecular nature can be provided by measuring time-resolved fluorescence (TRF) spectra of LHCII complexes and their aggregates. Previously [Chmeliov et al., Nat. Plants 2, 16045 (2016)], we analysed the corresponding TRF spectra using the multivariate curve resolution method and proposed a three-state model to describe the spectroscopic data. Usually, such data is described in terms of global analysis resulting in decay or evolution-associated spectra. In this work, we apply such analysis to the TRF data of LHCII aggregates and show that, although mathematically feasible, it cannot be directly related to the physical kinetic model. Nevertheless, a careful examination supplemented with additional spectroscopic information still results in the same three-state model proposed before.