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

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.