# Preparative isolation and preliminary characterization of LHCII trimers and PSII monomers from Posidonia oceanica L

## TL;DR

This paper describes a new method to isolate and study key photosynthetic components from the marine plant Posidonia oceanica.

## Contribution

A novel chromatography-based workflow for isolating LHCII trimers and PSII monomers from P. oceanica is developed.

## Key findings

- A procedure for thylakoid solubilization was developed to isolate LHCII trimers and PSII monomers.
- Mass spectrometry and peptide homology analysis identified the isolated proteins despite the lack of a curated proteome.
- The workflow enables functional and structural studies of P. oceanica's photosynthetic apparatus.

## Abstract

Posidonia oceanica L. is a vascular marine plant that represents a relevant case study in plant physiology due to its phylogenetic position, ecological adaptations, and, in particular, the specialization of its photosynthetic apparatus. Here, we present a procedure for fractional thylakoid solubilization, in which a crude leaf extract obtained by blending is preliminarily depleted of the polyphenolic fraction and subsequently subjected to stepwise solubilization. The resulting thylakoid extracts, processed through a chromatographic workflow, enable the preparative isolation of trimeric Light-Harvesting Complex II and monomeric Photosystem II core complex. Protein identification was supported by mass spectrometry, with peptide homology analysis used for the assignment due to the absence of a curated proteome for P. oceanica. The resulting fractions enable downstream characterization, establishing the first chromatography-based preparative workflow for functional and structural investigations of the photosynthetic apparatus of this ecologically unique species.

The online version contains supplementary material available at 10.1007/s11120-026-01196-3.