Photo-CIDNP in the Reaction Center of the Diatom Cyclotella meneghiniana Observed by ¹³C MAS NMR

Abstract

Photo-CIDNP in the reaction center of the diatom Cyclotella meneghiniana observed by 13 C MAS NMRThe solid-state photo-CIDNP effect in a new kingdom of the tree of life Abstract: Photo-CIDNP MAS NMR presents a unique tool to obtain insight into the photosynthetic reaction centers (RCs) of bacteria and plants. Using the dramatic enhancement of sensitivity and selectivity of the solid-state photo-CIDNP effect, structural as well as functional information can be obtained from the cofactor molecules forming a light-induced spin-correlated radical pair (SCRP) in a given reaction center. Here we demonstrate that the effect can be observed in a further species, which belongs neither to the plant nor the bacteria kingdom. Cyclotella (C.) meneghiniana is a member of the diatom phylum and, therefore, belongs to the kingdom of chromista. Chromista are some of the most productive organisms in nature, even in comparison to trees and terrestrial grasses. The observation of the effect in chromista indicates that the effect occurs in all photosynthetic organisms and completes the list with the last phototrophic kingdoms. Our data also demonstrate that the photo-and spin-chemical machineries of photosystem I of plants and chromista are very similar with respect to structure as well as function.

15N photo-CIDNP MAS NMR on both photosystems and magnetic field-dependent 13C photo-CIDNP MAS NMR in photosystem II of the diatom Phaeodactylum tricornutum

“…The data imply that the sign change is most probably due to a decrease of the extent of the DR which is itself caused by a shorter-lived molecular triplet state at higher field which is quenched, if there is a carotenoid nearby. A previous work on PS I core complexes showed that the DR mechanism is not active or contributes only very slightly to the total nuclear spin polarisation leading to typically emissive signals (Zill et al 2017b). It was shown that the extent of the effect is increasing with decreasing magnetic field (Thamarath et al 2012).…”

“…The most deshielded signal appears emissively at 192.1 ppm and can be assigned to a carbon at the 13 1 -position of Chl a. The signal resonates at the same position like a donor Chl a observed in PS I of the diatom C. meneghiniana (Zill et al 2017b) and the signal is also observed in PS II of P. tricornutum (see chapter 3.3.1), which does not allow to assign this signal to a specific cofactor. The emissive resonance at 168.3 ppm can be assigned to a C-19 position and is most suitable for a Chl a cofactor.…”

“…The sample was prepared following a similar protocol as applied for a photo-CIDNP active PS I preparation from the diatom C. meneghiniana (Zill et al 2017b) A detailed version of the protocol is described by Lepetit et al 2007 Cells were harvested by centrifugation for 5 min at 1,000 g and resuspended in buffer A (10 mM 2-(N-Morpholino)ethanesulfonic acid (MES) pH 6.5, 2 mM KCl, 5 mM ethylene-diaminetetraacetic acid (EDTA), and 1 M sorbitol). Cell lysis was performed with a pre-chilled French Pressure cell (Thermo Spectronic, UK) at 12,000 psi.…”

“…Today the centric forms are divided into two classes: Coscinodiscophyceae and Mediophyceae. The diatom for which the solid-state photo-CIDNP effect has been shown before, Cyclotella meneghiniana, belongs to the latter class (Zill et al 2017b). It is assumed that there are up to 200,000 species in the diatom phylum, making them the most speciose algae (Mann and Droop 1996).…”

Analysis of the Electronic Structure of the Special Pair of a Bacterial Photosynthetic Reaction Center by 13C Photochemically Induced Dynamic Nuclear Polarization Magic‐Angle Spinning NMR Using a Double‐Quantum Axis

“…The high sensitivity and selectivity of the photo-CIDNP MAS NMR experiment provide an excellent analytical tool for studying photosynthetic SCRPs in great detail (29,30). This method has been applied to various photosynthetic systems (31)(32)(33)(34).…”