Regional quantification of glycosaminoglycans and their association with collagen fibril ultrastructure in the sclera following enzymatic degradation.

Sclera biomechanics play an important role in clear vision. Understanding the biomechanical, composition and ultrastructural topography of the sclera may help provide better insight into eye health. Some prior research has investigated the ultrastructural and biomechanical properties of the sclera in relation to regional variations.

Characterization of the Structure and Function of the Photosynthetic RC-LH1 Core Supercomplex From Rhodospirillum rubrum.

Photosynthetic reaction center-light harvesting 1 (RC-LH1) core supercomplexes are essential for energy capture and electron transport in purple bacteria. Rhodospirillum rubrum, a model organism for bacterial photosynthesis, features an RC-LH1 architecture with a closed LH1 ring and lacks the peripheral LH2 antenna in the photosynthetic membranes. How this unique RC-LH1 supercomplex performs energy transfer and quinone transport remains unclear.

Symmetry-adjusted cryo-EM analysis unveils the detailed linker protein CsoS2 interactions within the α-carboxysome shell.

Excessive symmetry in cryo-EM data processing can distort key structural details of bacterial microcompartments, highlighting the importance of balanced symmetry for accurate structural insights.

Tunneling Mechanisms of Quinones in Photosynthetic Reaction Center-Light Harvesting 1 Supercomplexes.

In photosynthesis, light energy is absorbed and transferred to the reaction center, ultimately leading to the reduction of quinone molecules through the electron transfer chain. The oxidation and reduction of quinones generate an electrochemical potential difference used for adenosine triphosphate synthesis. The trafficking of quinone/quinol molecules between electron transport components has been a long-standing question.

Carboxysome Shell Protein CcmK2 Assembles into Monodisperse and pH-Reversible Microparticles.

Synthetic nano- and microparticles have become essential tools in biotechnology. Protein-based compartments offer distinct advantages over synthetic particles, such as biodegradability and biocompatibility, but their development is still in its infancy. Bacterial microcompartments (BMCs) are protein-based organelles consisting of a protein shell encapsulating an enzymatic core.

Engineering Rubisco condensation in chloroplasts to manipulate plant photosynthesis.

Although Rubisco is the most abundant enzyme globally, it is inefficient for carbon fixation because of its low turnover rate and limited ability to distinguish CO and O, especially under high O conditions. To address these limitations, phytoplankton, including cyanobacteria and algae, have evolved CO-concentrating mechanisms (CCM) that involve compartmentalizing Rubisco within specific structures, such as carboxysomes in cyanobacteria or pyrenoids in algae. Engineering plant chloroplasts to establish similar structures for compartmentalizing Rubisco has attracted increasing interest for improving photosynthesis and carbon assimilation in crop plants.

Light-Driven Hybrid Nanoreactor Harnessing the Synergy of Carboxysomes and Organic Frameworks for Efficient Hydrogen Production.

Synthetic photobiocatalysts are promising catalysts for valuable chemical transformations by harnessing solar energy inspired by natural photosynthesis. However, the synergistic integration of all of the components for efficient light harvesting, cascade electron transfer, and efficient biocatalytic reactions presents a formidable challenge. In particular, replicating intricate multiscale hierarchical assembly and functional segregation involved in natural photosystems, such as photosystems I and II, remains particularly demanding within artificial structures.

Rubisco packaging and stoichiometric composition of the native β-carboxysome in Synechococcus elongatus PCC7942.

Carboxysomes are anabolic bacterial microcompartments that play an essential role in CO2 fixation in cyanobacteria. This self-assembling proteinaceous organelle uses a polyhedral shell constructed by hundreds of shell protein paralogs to encapsulate the key CO2-fixing enzymes Rubisco and carbonic anhydrase. Deciphering the precise arrangement and structural organization of Rubisco enzymes within carboxysomes is crucial for understanding carboxysome formation and overall functionality.

Engineering CO-fixing modules in Escherichia coli via efficient assembly of cyanobacterial Rubisco and carboxysomes.

Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) is the central enzyme for conversion of atmospheric CO into organic molecules, playing a crucial role in the global carbon cycle. In cyanobacteria and some chemoautotrophs, Rubisco complexes, together with carbonic anhydrase, are enclosed within specific proteinaceous microcompartments known as carboxysomes. The polyhedral carboxysome shell ensures the dense packaging of Rubisco and creates a high-CO internal environment to facilitate CO fixation.

Architectures of photosynthetic RC-LH1 supercomplexes from .

The reaction center-light-harvesting complex 1 (RC-LH1) plays an essential role in the primary reactions of bacterial photosynthesis. Here, we present high-resolution structures of native monomeric and dimeric RC-LH1 supercomplexes from () using cryo-electron microscopy. The RC-LH1 monomer is composed of an RC encircled by an open LH1 ring comprising 15 αβ heterodimers and a PufX transmembrane polypeptide.

Rubisco packaging and stoichiometric composition of a native β-carboxysome.

Carboxysomes are anabolic bacterial microcompartments that play an essential role in carbon fixation in cyanobacteria. This self-assembling proteinaceous organelle encapsulates the key CO-fixing enzymes, Rubisco and carbonic anhydrase, using a polyhedral shell constructed by hundreds of shell protein paralogs. Deciphering the precise arrangement and structural organization of Rubisco enzymes within carboxysomes is crucial for understanding the formation process and overall functionality of carboxysomes.

Molecular interactions of the chaperone CcmS and carboxysome shell protein CcmK1 that mediate β-carboxysome assembly.

The carboxysome is a natural proteinaceous organelle for carbon fixation in cyanobacteria and chemoautotrophs. It comprises hundreds of protein homologs that self-assemble to form a polyhedral shell structure to sequester cargo enzymes, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), and carbonic anhydrases. How these protein components assemble to construct a functional carboxysome is a central question in not only understanding carboxysome structure and function but also synthetic engineering of carboxysomes for biotechnological applications.

Structure of cryptophyte photosystem II-light-harvesting antennae supercomplex.

Cryptophytes are ancestral photosynthetic organisms evolved from red algae through secondary endosymbiosis. They have developed alloxanthin-chlorophyll a/c2-binding proteins (ACPs) as light-harvesting complexes (LHCs). The distinctive properties of cryptophytes contribute to efficient oxygenic photosynthesis and underscore the evolutionary relationships of red-lineage plastids.

Conjugated Polymer/Recombinant Biohybrid Systems for Photobiocatalytic Hydrogen Production.

Biohybrid photocatalysts are composite materials that combine the efficient light-absorbing properties of synthetic materials with the highly evolved metabolic pathways and self-repair mechanisms of biological systems. Here, we show the potential of conjugated polymers as photosensitizers in biohybrid systems by combining a series of polymer nanoparticles with engineered cells. Under simulated solar light irradiation, the biohybrid system consisting of fluorene/dibenzo []thiophene sulfone copolymer (LP41) and recombinant (i.

Architecture of symbiotic dinoflagellate photosystem I-light-harvesting supercomplex in Symbiodinium.

Symbiodinium are the photosynthetic endosymbionts for corals and play a vital role in supplying their coral hosts with photosynthetic products, forming the nutritional foundation for high-yield coral reef ecosystems. Here, we determine the cryo-electron microscopy structure of Symbiodinium photosystem I (PSI) supercomplex with a PSI core composed of 13 subunits including 2 previously unidentified subunits, PsaT and PsaU, as well as 13 peridinin-Chl a/c-binding light-harvesting antenna proteins (AcpPCIs). The PSI-AcpPCI supercomplex exhibits distinctive structural features compared to their red lineage counterparts, including extended termini of PsaD/E/I/J/L/M/R and AcpPCI-1/3/5/7/8/11 subunits, conformational changes in the surface loops of PsaA and PsaB subunits, facilitating the association between the PSI core and peripheral antennae.

Nanoengineering Carboxysome Shells for Protein Cages with Programmable Cargo Targeting.

Protein nanocages have emerged as promising candidates for enzyme immobilization and cargo delivery in biotechnology and nanotechnology. Carboxysomes are natural proteinaceous organelles in cyanobacteria and proteobacteria and have exhibited great potential in creating versatile nanocages for a wide range of applications given their intrinsic characteristics of self-assembly, cargo encapsulation, permeability, and modularity. However, how to program intact carboxysome shells with specific docking sites for tunable and efficient cargo loading is a key question in the rational design and engineering of carboxysome-based nanostructures.

Dynamic Changes in the Thylakoid Proteome of Cyanobacteria during Light-Regulated Thylakoid Membrane Development.

Cyanobacteria were among the oldest organisms to undertake oxygenic photosynthesis and have an essential impact on the atmosphere and carbon/nitrogen cycles on the planet. The thylakoid membrane of cyanobacteria represents an intricate compartment that houses a variety of multi-component (pigment-)protein complexes, assembly factors, and regulators, as well as transporters involved in photosynthetic light reactions, and respiratory electron transport. How these protein components are incorporated into membranes during thylakoid formation and how individual complexes are regulated to construct the functional machinery remains elusive.

Making the connections: physical and electric interactions in biohybrid photosynthetic systems.

Biohybrid photosynthesis systems, which combine biological and non-biological materials, have attracted recent interest in solar-to-chemical energy conversion. However, the solar efficiencies of such systems remain low, despite advances in both artificial photosynthesis and synthetic biology. Here we discuss the potential of conjugated organic materials as photosensitisers for biological hybrid systems compared to traditional inorganic semiconductors.

Chemoautotrophic production of gaseous hydrocarbons, bioplastics and osmolytes by a novel Halomonas species.

Background: Production of relatively low value, bulk commodity chemicals and fuels by microbial species requires a step-change in approach to decrease the capital and operational costs associated with scaled fermentation. The utilisation of the robust and halophilic industrial host organisms of the genus Halomonas could dramatically decrease biomanufacturing costs owing to their ability to grow in seawater, using waste biogenic feedstocks, under non-sterile conditions.

Results: We describe the isolation of Halomonas rowanensis, a novel facultative chemoautotrophic species of Halomonas from a natural brine spring.

Intrinsically disordered CsoS2 acts as a general molecular thread for α-carboxysome shell assembly.

Carboxysomes are a paradigm of self-assembling proteinaceous organelles found in nature, offering compartmentalisation of enzymes and pathways to enhance carbon fixation. In α-carboxysomes, the disordered linker protein CsoS2 plays an essential role in carboxysome assembly and Rubisco encapsulation. Its mechanism of action, however, is not fully understood.

Unravelling the Roles of Integral Polypeptides in Excitation Energy Transfer of Photosynthetic RC-LH1 Supercomplexes.

Elucidating the photosynthetic processes that occur within the reaction center-light-harvesting 1 (RC-LH1) supercomplexes from purple bacteria is crucial for uncovering the assembly and functional mechanisms of natural photosynthetic systems and underpinning the development of artificial photosynthesis. Here, we examined excitation energy transfer of various RC-LH1 supercomplexes of using transient absorption spectroscopy, coupled with lifetime density analysis, and studied the roles of the integral transmembrane polypeptides, PufX and PufY, in energy transfer within the RC-LH1 core complex. Our results show that the absence of PufX increases both the LH1 → RC excitation energy transfer lifetime and distribution due to the role of PufX in defining the interaction and orientation of the RC within the LH1 ring.

Structural diversity and modularity of photosynthetic RC-LH1 complexes.

Bacterial photosynthesis is essential for sustaining life on Earth as it aids in carbon assimilation, atmospheric composition, and ecosystem maintenance. Many bacteria utilize anoxygenic photosynthesis to convert sunlight into chemical energy while producing organic matter. The core machinery of anoxygenic photosynthesis performed by purple photosynthetic bacteria and Chloroflexales is the reaction center-light-harvesting 1 (RC-LH1) pigment-protein supercomplex.