The effects of combining naturally evolved photosynthetic pigment-protein complexes with inorganic functional materials, especially plasmonically active metallic nanostructures, have been a widely studied topic in the last few decades. Besides other applications, it seems to be reasonable using such hybrid systems for designing future biomimetic solar cells. In this paper, we describe selected results that point out to various aspects of the interactions between photosynthetic complexes and plasmonic excitations in Silver Island Films (SIFs). In addition to simple light-harvesting complexes, like peridinin-chlorophyll-protein (PCP) or the Fenna-Matthews-Olson (FMO) complex, we also discuss the properties of large, photosynthetic reaction centers (RCs) and Photosystem I (PSI)-both prokaryotic PSI core complexes and eukaryotic PSI supercomplexes with attached antenna clusters (PSI-LHCI)-deposited on SIF substrates.

• Keywords
• MEF, SIF, biohybrid structures, photosynthetic complexes,
• MeSH
• Chlorophyll A metabolism   MeSH
• Spectrometry, Fluorescence methods   MeSH
• Formaldehyde chemistry   MeSH
• Photosynthesis * MeSH
• Photosystem I Protein Complex metabolism   MeSH
• Glucose chemistry   MeSH
• Carotenoids metabolism   MeSH
• Nanostructures chemistry   ultrastructure   MeSH
• Silver chemistry   MeSH
• Light-Harvesting Protein Complexes metabolism   MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Chlorophyll A MeSH
• Formaldehyde MeSH
• Photosystem I Protein Complex MeSH
• Glucose MeSH
• Carotenoids MeSH
• peridinin MeSH Browser
• Silver MeSH
• Light-Harvesting Protein Complexes MeSH

In the extremophile bacterium Deinococcus radiodurans, the outermost surface layer is tightly connected with the rest of the cell wall. This integrated organization provides a compact structure that shields the bacterium against environmental stresses. The fundamental unit of this surface layer (S-layer) is the S-layer deinoxanthin-binding complex (SDBC), which binds the carotenoid deinoxanthin and provides both, thermostability and UV radiation resistance. However, the structural organization of the SDBC awaits elucidation. Here, we report the isolation of the SDBC with a gentle procedure consisting of lysozyme treatment and solubilization with the nonionic detergent n-dodecyl-β-d-maltoside, which preserved both hydrophilic and hydrophobic components of the SDBC and allows the retention of several minor subunits. As observed by low-resolution single-particle analysis, we show that the complex possesses a porin-like structural organization, but is larger than other known porins. We also noted that the main SDBC component, the protein DR_2577, shares regions of similarity with known porins. Moreover, results from electrophysiological assays with membrane-reconstituted SDBC disclosed that it is a nonselective channel that has some peculiar gating properties, but also exhibits behavior typically observed in pore-forming proteins, such as porins and ionic transporters. The functional properties of this system and its porin-like organization provide information critical for understanding ion permeability through the outer cell surface of S-layer-carrying bacterial species.

• Keywords
• Deinococcus radiodurans, S-layer, S-layer deinoxanthin–binding complex (SDBC), electron microscopy (EM), electrophysiology, gating, mass spectrometry (MS), membrane protein, porin-like complex, protein structure, stress resistance, structure–function,
• MeSH
• Bacterial Proteins chemistry   genetics   MeSH
• Cell Membrane chemistry   MeSH
• Cell Wall chemistry   MeSH
• Deinococcus chemistry   genetics   MeSH
• Carotenoids chemistry   MeSH
• Membrane Glycoproteins chemistry   MeSH
• Multiprotein Complexes chemistry   genetics   MeSH
• Porins chemistry   MeSH
• Protein Binding genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Bacterial Proteins MeSH
• deinoxanthin MeSH Browser
• Carotenoids MeSH
• Membrane Glycoproteins MeSH
• Multiprotein Complexes MeSH
• Porins MeSH
• S-layer proteins MeSH Browser

Survival of phototrophic organisms depends on their ability to collect and convert enough light energy to support their metabolism. Phototrophs can extend their absorption cross section by using diverse pigments and by tuning the properties of these pigments via pigment-pigment and pigment-protein interaction. It is well known that some cyanobacteria can grow in heavily shaded habitats by utilizing far-red light harvested with far-red-absorbing chlorophylls d and f. We describe a red-shifted light-harvesting system based on chlorophyll a from a freshwater eustigmatophyte alga Trachydiscus minutus (Eustigmatophyceae, Goniochloridales). A comprehensive characterization of the photosynthetic apparatus of T. minutus is presented. We show that thylakoid membranes of T. minutus contain light-harvesting complexes of several sizes differing in the relative amount of far-red chlorophyll a forms absorbing around 700 nm. The pigment arrangement of the major red-shifted light-harvesting complex is similar to that of the red-shifted antenna of a marine alveolate alga Chromera velia. Evolutionary aspects of the algal far-red light-harvesting complexes are discussed. The presence of these antennas in eustigmatophyte algae opens up new ways to modify organisms of this promising group for effective use of far-red light in mass cultures.

• Keywords
• Chromatic acclimation, Eustigmatophyta, Light-harvesting protein, Oligomeric LHC, Red-shifted LHC, Violaxanthin,
• MeSH
• Pigments, Biological metabolism   MeSH
• Diuron MeSH
• Spectrometry, Fluorescence MeSH
• Stramenopiles metabolism   radiation effects   MeSH
• Membrane Proteins metabolism   MeSH
• Fresh Water * MeSH
• Light * MeSH
• Light-Harvesting Protein Complexes metabolism   MeSH
• Temperature MeSH
• Thylakoids metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Pigments, Biological MeSH
• Diuron MeSH
• Membrane Proteins MeSH
• Light-Harvesting Protein Complexes MeSH