Tuning of a Hydrogen-Bonded Organic Framework by Liquid-Assisted Mechanosynthesis between Trans-Aconitic Acid and Isonicotinamide.

Cocrystallization of trans-aconitic acid (TACA) and isonicotinamide (INA) using liquid assisted mechanochemical grinding results in a unique supramolecular hydrogen-bonded organic framework (HOF) system encapsulating various organic solvents (liquid guest) with the formation of channel inclusion compounds. Dimension and shape of the framework is dependent on the solvent used during liquid assisted grinding (LAG). Although crystal structure of the cocrystal (TACA) ⋅ (INA) ⋅ (HO)@(INA) has been determined by Single Crystal X-ray diffraction (SCXRD), crystal structures of 3 cocrystal HOFs were determined by microcrystal electron diffraction (MicroED) and synchrotron X-ray diffraction due to lack of suitable single crystal.

Diatom pyrenoids are encased in a protein shell that enables efficient CO fixation.

Pyrenoids are subcompartments of algal chloroplasts that increase the efficiency of Rubisco-driven CO fixation. Diatoms fix up to 20% of global CO, but their pyrenoids remain poorly characterized. Here, we used in vivo photo-crosslinking to identify pyrenoid shell (PyShell) proteins, which we localized to the pyrenoid periphery of model pennate and centric diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana.

The unique allosteric property of crocodilian haemoglobin elucidated by cryo-EM.

The principal effect controlling the oxygen affinity of vertebrate haemoglobins (Hbs) is the allosteric switch between R and T forms with relatively high and low oxygen affinity respectively. Uniquely among jawed vertebrates, crocodilians possess Hb that shows a profound drop in oxygen affinity in the presence of bicarbonate ions. This allows them to stay underwater for extended periods by consuming almost all the oxygen present in the blood-stream, as metabolism releases carbon dioxide, whose conversion to bicarbonate and hydrogen ions is catalysed by carbonic anhydrase.

Structural Analyses of Designed α-Helix and β-Sheet Peptide Nanofibers Using Solid-State Nuclear Magnetic Resonance and Cryo-Electron Microscopy and Introduction of Structure-Based Metal-Responsive Properties.

The 21-residue peptide α3, which is artificially designed and consists of three repeats of 7 residues, is known to rapidly assemble into the α-helix nanofiber. However, its molecular structure within the fiber has not yet been fully elucidated. Thus, we conducted a thorough investigation of the fiber's molecular structure using solid-state NMR and other techniques.

Combined computed tomography and C-arm resuscitation room system (CTCARM) is associated with decreased time to definitive hemostasis and reduces preperitoneal pelvic packing maneuvers in severe pelvic trauma.

Objectives: Severe pelvic fracture concomitant with massive bleeding is potentially lethal, and intervention for hemorrhage control still depends on institutional supplies. With the recent installation of a CT and C-arm combined resuscitation room system (CTCARM) for treatment of trauma patients in our institution, the strategic process and options for hemorrhage control after pelvic fracture have changed. We retrospectively reviewed the procedures we performed and their outcomes.

Factors associated with the outcome of patients with COVID-19 requiring mechanical ventilation: A single-center observational study in Japan.

Aim: Coronavirus disease (COVID-19) spread worldwide, and was declared as a pandemic by the World Health Organization. Despite numerous studies in the last few years, the factors associated with the outcomes of patients with COVID-19 requiring mechanical ventilation remain unclear. The prediction of ventilator weaning and mortality using the data obtained at the time of intubation could be beneficial for establishing appropriate treatment strategies and obtaining informed consent.

Three structures of PSI-LHCI from Chlamydomonas reinhardtii suggest a resting state re-activated by ferredoxin.

Photosystem I (PSI) from the green alga Chlamydomonas reinhardtii, with various numbers of membrane bound antenna complexes (LHCI), has been described in great detail. In contrast, structural characterization of soluble binding partners is less advanced. Here, we used X-ray crystallography and single particle cryo-EM to investigate three structures of the PSI-LHCI supercomplex from Chlamydomonas reinhardtii.

Structural insights into blue-green light utilization by marine green algal light harvesting complex II at 2.78 Å.

Light-harvesting complex II (LHCII) present in plants and green algae absorbs solar energy to promote photochemical reactions. A marine green macroalga, , exhibits the unique characteristic of absorbing blue-green light from the sun during photochemical reactions while being underwater owing to the presence of pigment-altered LHCII called siphonaxanthin-chlorophyll binding protein (SCP). In this study, we determined the structure of SCP at a resolution of 2.

Isolation and structure of the fibril protein, a major component of the internal ribbon for swimming.

, which are known pathogens and commensals of arthropods and plants, are helical-shaped bacteria that lack a peptidoglycan layer. swim by alternating between left- and right-handed helicity. Of note, this system is not related to flagellar motility, which is widespread in bacteria.

Cryo-EM structures of the translocational binary toxin complex CDTa-bound CDTb-pore from Clostridioides difficile.

Some bacteria express a binary toxin translocation system, consisting of an enzymatic subunit and translocation pore, that delivers enzymes into host cells through endocytosis. The most clinically important bacterium with such a system is Clostridioides difficile (formerly Clostridium). The CDTa and CDTb proteins from its system represent important therapeutic targets.

Structure of cyanobacterial photosystem I complexed with ferredoxin at 1.97 Å resolution.

Photosystem I (PSI) is a light driven electron pump transferring electrons from Cytochrome c (Cyt c) to Ferredoxin (Fd). An understanding of this electron transfer process is hampered by a paucity of structural detail concerning PSI:Fd interface and the possible binding sites of Cyt c. Here we describe the high resolution cryo-EM structure of Thermosynechococcus elongatus BP-1 PSI in complex with Fd and a loosely bound Cyt c.

Structures of multisubunit membrane complexes with the CRYO ARM 200.

Progress in structural membrane biology has been significantly accelerated by the ongoing 'Resolution Revolution' in cryo-electron microscopy (cryo-EM). In particular, structure determination by single-particle analysis has evolved into the most powerful method for atomic model building of multisubunit membrane protein complexes. This has created an ever-increasing demand in cryo-EM machine time, which to satisfy is in need of new and affordable cryo-electron microscopes.

Structural insight into the activation mechanism of MrgD with heterotrimeric Gi-protein revealed by cryo-EM.

MrgD, a member of the Mas-related G protein-coupled receptor (MRGPR) family, has high basal activity for Gi activation. It recognizes endogenous ligands, such as β-alanine, and is involved in pain and itch signaling. The lack of a high-resolution structure for MrgD hinders our understanding of whether its activation is ligand-dependent or constitutive.

Chained Structure of Dimeric F-like ATPase in Mycoplasma mobile Gliding Machinery.

Mycoplasma mobile, a fish pathogen, exhibits gliding motility using ATP hydrolysis on solid surfaces, including animal cells. The gliding machinery can be divided into surface and internal structures. The internal structure of the motor is composed of 28 so-called "chains" that are each composed of 17 repeating protein units called "particles.

Native flagellar MS ring is formed by 34 subunits with 23-fold and 11-fold subsymmetries.

The bacterial flagellar MS ring is a transmembrane complex acting as the core of the flagellar motor and template for flagellar assembly. The C ring attached to the MS ring is involved in torque generation and rotation switch, and a large symmetry mismatch between these two rings has been a long puzzle, especially with respect to their role in motor function. Here, using cryoEM structural analysis of the flagellar basal body and the MS ring formed by full-length FliF from Salmonella enterica, we show that the native MS ring is formed by 34 FliF subunits with no symmetry variation.

Cryo-EM structure of a functional monomeric Photosystem I from Thermosynechococcus elongatus reveals red chlorophyll cluster.

A high-resolution structure of trimeric cyanobacterial Photosystem I (PSI) from Thermosynechococcus elongatus was reported as the first atomic model of PSI almost 20 years ago. However, the monomeric PSI structure has not yet been reported despite long-standing interest in its structure and extensive spectroscopic characterization of the loss of red chlorophylls upon monomerization. Here, we describe the structure of monomeric PSI from Thermosynechococcus elongatus BP-1.

Two Distinct Conformations in 34 FliF Subunits Generate Three Different Symmetries within the Flagellar MS-Ring.

The bacterial flagellum is a protein nanomachine essential for bacterial motility. The flagellar basal body contains several ring structures. The MS-ring is embedded in the cytoplasmic membrane and is formed at the earliest stage of flagellar formation to serve as the base for flagellar assembly as well as a housing for the flagellar protein export gate complex.

Split conformation of Chaetomium thermophilum Hsp104 disaggregase.

Hsp104 and its bacterial homolog ClpB form hexameric ring structures and mediate protein disaggregation. The disaggregated polypeptide is thought to thread through the central channel of the ring. However, the dynamic behavior of Hsp104 during disaggregation remains unclear.

In Situ Structural Analysis of Leptospira spp. by Electron Cryotomography.

Spirochetes such as Treponema, Borrelia, and Leptospira species can rotate their bodies to swim in liquid environments by rotating periplasmic flagella or endoflagella, which are present inside the cell. Electron cryotomography (ECT) is an imaging technique that directly provides three-dimensional (3D) structures of cells and molecular complexes in their cellular environment at nanometer resolution. Here, I present a general protocol of ECT that covers the sample preparation, data collection, tilt series alignment, and tomographic reconstruction for visualization of intact periplasmic flagella in Leptospira spp.

Assembly mechanism of a supramolecular MS-ring complex to initiate bacterial flagellar biogenesis in species.

The bacterial flagellum is an organelle responsible for motility and has a rotary motor comprising the rotor and the stator. Flagellar biogenesis is initiated by the assembly of the MS-ring, a supramolecular complex embedded in the cytoplasmic membrane. The MS-ring consists of a few dozen copies of the transmembrane FliF protein, and is an essential core structure which is a part of the rotor.

Cryo-EM structures reveal translocational unfolding in the clostridial binary iota toxin complex.

The iota toxin produced by Clostridium perfringens type E is a binary toxin comprising two independent polypeptides: Ia, an ADP-ribosyltransferase, and Ib, which is involved in cell binding and translocation of Ia across the cell membrane. Here we report cryo-EM structures of the translocation channel Ib-pore and its complex with Ia. The high-resolution Ib-pore structure demonstrates a similar structural framework to that of the catalytic ϕ-clamp of the anthrax protective antigen pore.