Versatile Surface Electrodes for Combined Electrophysiology and Two-Photon Imaging of the Mouse Central Nervous System

Understanding and modulating CNS function in physiological as well as pathophysiological contexts remains a significant ambition in research and clinical applications. The investigation of the multifaceted CNS cell types including their interactions and contributions to neural function requires a combination of the state-of-the-art in vivo electrophysiology and imaging techniques. We developed a novel type of liquid crystal polymer (LCP) surface micro-electrode manufactured in three customized designs with up to 16 channels for recording and stimulation of brain activity. All designs include spare central spaces for simultaneous 2P-imaging. Nanoporous platinum-plated contact sites ensure a low impedance and high current transfer. The epidural implantation of the LCP micro-electrodes could be combined with standard cranial window surgery. The epidurally positioned electrodes did not only display long-term biocompatibility, but we also observed an additional stabilization of the underlying CNS tissue. We demonstrate the electrode’s versatility in combination with in vivo 2P-imaging by monitoring anesthesia-awake cycles of transgenic mice with GCaMP3 expression in neurons or astrocytes. Cortical stimulation and simultaneous 2P Ca2+ imaging in neurons or astrocytes highlighted the astrocytes’ integrative character in neuronal activity processing. Furthermore, we confirmed that spontaneous astroglial Ca2+ signals are dampened under anesthesia, while evoked signals in neurons and astrocytes showed stronger dependency on stimulation intensity rather than on various levels of anesthesia. Finally, we show that the electrodes provide recordings of the electrocorticogram (ECoG) with a high signal-to noise ratio and spatial signal differences which help to decipher brain activity states during experimental procedures. Summarizing, the novel LCP surface micro-electrode is a versatile, convenient, and reliable tool to investigate brain function in vivo.

Ternary aromatic and anti-aromatic clusters derived from the hypho species [Sn2Sb5]3−

Heterometallic clusters have attracted broad interests in the synthetic chemistry due to their various coordination modes and potential applications in heterogeneous catalysis. Here we report the synthesis, experimental, and theoretical characterizations of four ternary clusters ([M2(CO)6Sn2Sb5]3− (M = Cr, Mo), and [(MSn2Sb5)2]4−, (M = Cu, Ag)) in the process of capturing the hypho- [Sn2Sb5]3− in ethylenediamine (en) solution. We show that the coordination of the binary anion to transition-metal ions or fragments provides additional stabilization due to the formation of locally σ-aromatic units, producing a spherical aromatic shielding region in the cages. While in the case of [Mo2(CO)6Sn2Sb5]3− stabilization arises from locally σ-aromatic three-centre and five-centre two-electron bonds, aromatic islands in [(AgSn2Sb5)2]4− and [(CuSn2Sb5)2]4− render them globally antiaromatic. This work describes the coordination chemistry of the versatile building block [Sn2Sb5]3−, thus providing conceptual advances in the field of metal-metal bonding in clusters.

Bioactivity of Chitosan-Based Particles Loaded with Plant-Derived Extracts for Biomedical Applications: Emphasis on Antimicrobial Fiber-Based Systems

Marine-derived chitosan (CS) is a cationic polysaccharide widely studied for its bioactivity, which is mostly attached to its primary amine groups. CS is able to neutralize reactive oxygen species (ROS) from the microenvironments in which it is integrated, consequently reducing cell-induced oxidative stress. It also acts as a bacterial peripheral layer hindering nutrient intake and interacting with negatively charged outer cellular components, which lead to an increase in the cell permeability or to its lysis. Its biocompatibility, biodegradability, ease of processability (particularly in mild conditions), and chemical versatility has fueled CS study as a valuable matrix component of bioactive small-scaled organic drug-delivery systems, with current research also showcasing CS’s potential within tridimensional sponges, hydrogels and sutures, blended films, nanofiber sheets and fabric coatings. On the other hand, renewable plant-derived extracts are here emphasized, given their potential as eco-friendly radical scavengers, microbicidal agents, or alternatives to antibiotics, considering that most of the latter have induced bacterial resistance because of excessive and/or inappropriate use. Loading them into small-scaled particles potentiates a strong and sustained bioactivity, and a controlled release, using lower doses of bioactive compounds. A pH-triggered release, dependent on CS’s protonation/deprotonation of its amine groups, has been the most explored stimulus for that control. However, the use of CS derivatives, crosslinking agents, and/or additional stabilization processes is enabling slower release rates, following extract diffusion from the particle matrix, which can find major applicability in fiber-based systems within ROS-enriched microenvironments and/or spiked with microbes. Research on this is still in its infancy. Yet, the few published studies have already revealed that the composition, along with an adequate drug release rate, has an important role in controlling an existing infection, forming new tissue, and successfully closing a wound. A bioactive finishing of textiles has also been promoting high particle infiltration, superior washing durability, and biological response.

Crystal structure and molecular docking study of (E)-2-{[(E)-2-hydroxy-5-methylbenzylidene]hydrazinylidene}-1,2-diphenylethan-1-one

The title compound, C22H18N2O2, is a Schiff base that exists in the phenol–imine tautomeric form and adopts an E configuration with respect to the C=N bond. The molecular structure is stabilized by an O—H...N hydrogen bond, forming an S(6) ring motif. In the crystal, pairs of C—H...O hydrogen bonds link the molecules to form inversion dimers. Weak π–π stacking interactions along the a-axis direction provide additional stabilization of the crystal structure. The molecule is non-planar, the aromatic ring of the benzaldehyde residue being nearly perpendicular to the phenyl and 4-methylphenol rings with dihedral angles of 88.78 (13) and 82.26 (14)°, respectively. A molecular docking study between the title molecule and the COVID-19 main protease (PDB ID: 6LU7) was performed, showing that it is a potential agent because of its affinity and ability to adhere to the active sites of the protein.

Crystal structure and Hirshfeld surface analysis of a copper(II) complex containing 2-nitrobenzoate and tetramethylethylenediamine ligands

The reaction of copper(II) sulfatepentahydrate with 2-nitrobenzoic acid and N,N,N′,N′-tetramethylethylenediamine (TMEDA) in basic solution produces the complex bis(2-nitrobenzoato-κO)(N,N,N′,N′-tetramethylethylenediamine-κ2 N,N′)copper(II), [Cu(C7H4NO4)2(C6H16N2)] or [Cu(2-nitrobenzoate)2(tmeda)]. Each carboxylate group of the 2-nitrobenzoate ligand is coordinated by CuII atom in a monodentate fashion and two TMEDA ligand nitrogen atoms are coordinate by the metal center, giving rise to a distorted square-planar coordination environment. In the crystal, metal complexes are linked by centrosymmetric C—H...O hydrogen bonds, forming ribbons via a R 2 2(10) ring motif. These ribbons are linked by further C—H...O hydrogen bonds, leading to two-dimensional hydrogen-bonded arrays parallel to the bc plane. Weak π–π stacking interactions provide additional stabilization of the crystal structure. Hirshfeld surface analysis, dnorm and two-dimensional fingerprint plots were examined to verify the contributions of the different intermolecular contacts within the supramolecular structure. The major interactions of the complex are O...H/H...O (44.9%), H...H (34%) and C...H (14.5%).

Crystal structure and Hirshfeld surface analysis of 2-methyl-3-nitro-N-[(E)-(5-nitrothiophen-2-yl)methylidene]aniline

The title compound, C12H9N3O4S, synthesized by condensation of 5-nitrothiophene-2-carbaldehyde and 2-methyl-3-nitroaniline, crystallizes in the orthorhombic space group P212121. In the molecule, the aromatic benzene and thiophene rings are twisted with respect to each other, making a dihedral angle of 23.16 (7)°. In the crystal, molecules are linked by intermolecular C—H...O hydrogen bonds into chains extending along the c-axis direction. Weak π–π stacking interactions along the a-axis direction provide additional stabilization of the crystal structure. The roles of the various intermolecular interactions were clarified by Hirshfeld surface analysis, which reveals that the crystal packing is dominated by O...H (39%) and H...H (21.3%) contacts. The crystal studied was refined as a two-component inversion twin.

A Backwards-Tracking Lagrangian-Eulerian Method for Viscoelastic Two-Fluid Flows

A new Lagrangian–Eulerian method for the simulation of viscoelastic free surface flow is proposed. The approach is developed from a method in which the constitutive equation for viscoelastic stress is solved at Lagrangian nodes, which are convected by the flow, and interpolated to the Eulerian grid with radial basis functions. In the new method, a backwards-tracking methodology is employed, allowing for fixed locations for the Lagrangian nodes to be chosen a priori. The proposed method is also extended to the simulation of viscoelastic free surface flow with the volume of fluid method. No unstructured interpolation or node redistribution is required with the new approach. Furthermore, the total amount of Lagrangian nodes is significantly reduced when compared to the original Lagrangian–Eulerian method. Consequently, the method is more computationally efficient and robust. No additional stabilization technique, such as both-sides diffusion or reformulation of the constitutive equation, is necessary. A validation is performed with the analytic solution for transient and steady planar Poiseuille flow, with excellent results. Furthermore, the proposed method agrees well with numerical data from the literature for the viscoelastic die swell flow of an Oldroyd-B model. The capabilities to simulate viscoelastic free surface flow are also demonstrated through the simulation of a jet buckling case.

Non-catalytic-Region Mutations Conferring Transition of Class A β-Lactamases Into ESBLs

Despite class A ESBLs carrying substitutions outside catalytic regions, such as Cys69Tyr or Asn136Asp, have emerged as new clinical threats, the molecular mechanisms underlying their acquired antibiotics-hydrolytic activity remains unclear. We discovered that this non-catalytic-region (NCR) mutations induce significant dislocation of β3-β4 strands, conformational changes in critical residues associated with ligand binding to the lid domain, dynamic fluctuation of Ω-loop and β3-β4 elements. Such structural changes increase catalytic regions’ flexibility, enlarge active site, and thereby accommodate third-generation cephalosporin antibiotics, ceftazidime (CAZ). Notably, the electrostatic property around the oxyanion hole of Cys69Tyr ESBL is significantly changed, resulting in possible additional stabilization of the acyl-enzyme intermediate. Interestingly, the NCR mutations are as effective for antibiotic resistance by altering the structure and dynamics in regions mediating substrate recognition and binding as single amino-acid substitutions in the catalytic region of the canonical ESBLs. We believe that our findings are crucial in developing successful therapeutic strategies against diverse class A ESBLs, including the new NCR-ESBLs.

Cryo-EM analysis of human mitochondrial Hsp90 in multiple tetrameric states

Hsp90 is a ubiquitous molecular chaperone that mediates the folding and maturation of hundreds of “client” proteins. Although Hsp90s generally function as homodimers, recent discoveries suggested that the mitochondrion specific Hsp90 (TRAP1) also forms functionally relevant tetramers. The structural mechanism of tetramer formation remains elusive. Here we used a combination of solution, biochemical and cryo-electron microscopy (cryo-EM) approaches to confirm that, independent of nucleotide state, a subpopulation of TRAP1 exists as tetramers. Unexpectedly, cryo-EM reveals multiple tetramer conformations having TRAP1 dimers arranged in orthogonal, parallel, or antiparallel configurations. The cryo-EM structure of one of the orthogonal tetrameric states was determined at 3.5 Å resolution. Each of the two TRAP1 dimers is in a symmetric AMP·PNP-bound closed state with the tetramer being stabilized through three distinct dimer-dimer interaction sites. In unique ways, each of the three TRAP1 domains contributes to tetramer formation. In addition to tetramerization via direct dimer-dimer contacts, our structure suggests that additional stabilization could come from domain swapping between the dimers. These results expand our understanding of TRAP1 biology beyond the conventional view of a functional dimer and provide a platform to further explore the function and regulation of tetrameric TRAP1 in mitochondria.