The Mechanism of D2R Overactivation in Neurite Impairment and Oxidative Stress

Schizophrenia patients have altered neuronal connectivity, while the causal factor is not fully understood. Most antipsychotic drugs possess dopamine D2 receptor (D2R) antagonist property as a therapeutic target for reducing dopamine hyperactivity in schizophrenia. It is, however, not known whether the blockage of D2R is beneficial to neural connectivity. This study aimed to investigate the mechanisms of neurite lesion induced by D2R overactivation and prevention of such lesion by changing the D2R downstream signaling. Disrupted in schizophrenia 1 (DISC1) is a genetic risk factor for a wide range of psychiatric illnesses, including schizophrenia. DISC1 is a multifunctional scaffold protein that regulates neurogenesis and neural development in the adult brain. The excessive D2R-DISC1 complex is observed in the post-mortem brain of schizophrenia patients. However, the role of D2R-DISC1 complex in neurite outgrowth is unknown. The aim of Chapter 2 was to study whether neurite lesion induced by D2R overactivation is through the D2R-DISC1 complex. This study applied fluorescence resonance energy transfer (FRET) technique to quantify the interaction between D2R and DISC1 in primary cortical neurons. D2R specific agonist quinpirole increased the interaction of D2R and DISC1 by over activating D2R in primary cortical neurons. Furthermore, the excessive D2R-DISC1 complex reduced glycogen synthase kinase β (GSK-3β) phosphorylation. The increased D2R-DISC1 complex formation in conjunction with the decreased GSK-3β phosphorylation resulted in neurite impairment of cortical neurons. The antipsychotics haloperidol and aripiprazole disrupted the excessive formation of the D2R-DISC1 complex caused by D2R overactivation. However, only aripiprazole could reverse the downregulation of phosphorylated GSK3β caused by quinpirole. Aripiprazole displayed better preventative effect than haloperidol on neurite lesion induced by quinpirole, suggesting that aripiprazole and haloperidol may affect neuroplasticity via different signaling pathways. Also, both haloperidol and aripiprazole failed to rescue neurite lesion of primary cortical neurons from DISC1 mutant mice. In summary, the normal D2R-DISC1 complex signaling is critical for neurite outgrowth

Highly Covalent Ferric−Thiolate Bonds Exhibit Surprisingly Low Mechanical Stability

Depending on their nature, different chemical bonds show vastly different stability with covalent bonds being the most stable ones that rupture at forces above nanonewton. Studies have revealed that ferric−thiolate bonds are highly covalent and are conceived to be of high mechanical stability. Here, we used single molecule force spectroscopy techniques to directly determine the mechanical strength of such highly covalent ferric−thiolate bonds in rubredoxin. We observed that the ferric−thiolate bond ruptures at surprisingly low forces of ∼200 pN, significantly lower than that of typical covalent bonds, such as C−Si, S−S, and Au−thiolate bonds, which typically ruptures at >1.5 nN. And the mechanical strength of Fe−thiolate bonds is observed to correlate with the covalency of the bonds. Our results indicated that highly covalent Fe−thiolate bonds are mechanically labile and display features that clearly distinguish themselves from typical covalent bonds. Our study not only opens new avenues to investigating this important class of chemical bonds, but may also shed new lights on our understanding of the chemical nature of these metal thiolate bonds

Kinetic Measurement and Modeling of a Slow-Rate Diazo Coupling Reaction

The reaction network of the diazo coupling between 1-hydroxy-6-nitro-4-sulfonaphthalene-2-diazonium salt and 2-naphthol was identified through experimental methods. The kinetic experiments were conducted at the temperature range of 303–323 K. A kinetic model, which takes the decomposition of the diazonium salt into account, was established, and the kinetic parameters were estimated based on the experimental data. The model simulation results showed good agreement with the experimental data. Then, the effects of the reactant concentration, the molar ratio, and the reaction temperature were further investigated using the kinetic model. Finally, this kinetic model was coupled with a plug-flow reactor model and an axial dispersion model to reveal the influence of heat transfer and backmixing. This study can shed some light on the design and optimization of the industrial tubular reactors

Quantum Plexcitonic Sensing

While fundamental to quantum sensing, quantum state control has been traditionally limited to extreme conditions. This restricts the impact of the practical implementation of quantum sensing on a broad range of physical measurements. Plexcitons, however, provide a promising path under ambient conditions toward quantum state control and thus quantum sensing, owing to their origin from strong plasmon–exciton coupling. Herein, we harness plexcitons to demonstrate quantum plexcitonic sensing by strongly coupling excitonic particles to a plasmonic hyperbolic metasurface. As compared to classical sensing in the weak-coupling regime, our model of quantum plexcitonic sensing performs at a level that is ∼40 times more sensitive. Noise-modulated sensitivity studies reinforce the quantum advantage over classical sensing, featuring better sensitivity, smaller sensitivity uncertainty, and higher resilience against optical noise. The successful demonstration of quantum plexcitonic sensing opens the door for a variety of physical, chemical, and biological measurements by leveraging strongly coupled plasmon–exciton systems

Single-Molecule Force Spectroscopy Reveals the Dynamic HgS Coordination Site in the <i>De Novo</i>-Designed Metalloprotein α₃DIV

The de novo-designed metalloprotein α3DIV binds to mercury via three cysteine residues under dynamic conditions. An unusual trigonal three-coordinate HgS3 site is formed in the protein in basic solution, whereas a linear two-coordinate HgS2 site is formed in acidic solution. Furthermore, it is unknown whether the two coordinated cysteines in the HgS2 site are fixed or not, which may lead to more dynamics. However, the signal for HgS2 sites with different cysteines may be similar or may be averaged and indistinguishable. To circumvent this problem, we adopt a single-molecule approach to study one mercury site at a time. Using atomic force microscopy-based single-molecule force spectroscopy, the protein is unfolded, and the HgS site is ruptured. The results confirm the formation of HgS3 and HgS2 sites at different pH values. Moreover, it is found that any two of the three cysteines in the protein bind to mercury in the HgS2 site

Effect of the Competing Ligand on Ni-NTA/Histag Strength Revealed by Click Chemistry-Based Force Spectroscopy

The specific interaction between Ni-nitrilotriacetic acid and the six-histidine tag may be one of the most important coordination bonds utilized in biological research because of its wide application for recombinant protein purification. The complex stability is critical for target protein binding. Thus, measurement of the mechanical stability of the system was attempted soon after the invention of atomic force microscopy-based single-molecule force spectroscopy (AFM-SMFS) two decades ago. Moreover, the competing ligand imidazole and protons are the two critical factors for target protein elution. However, the mechanochemistry between the system and the imidazole/proton has not been determined. Here, an AFM-SMFS system using strain-promoted alkyne–azide cycloaddition and Cu-free click chemistry was used to characterize the system. Consequently, the destabilizing effect of the imidazole and proton on the interaction was revealed quantitatively, leading to a 3-fold increase in the bond dissociation rate

Elucidating the Growth Mechanism of Plasmonic Gold Nanostars with Tunable Optical and Photothermal Properties

Gold nanostars (GNSs) have received considerable attention in surface-enhanced spectroscopies, catalysis, biosensing, photothermal therapy, and photovoltaics because of their unique optical properties arising from the anisotropic structure. GNSs typically consisting of a central core and several protruding tips are usually synthesized by a seed-mediated growth approach, but the growth mechanism and optical properties have yet to be fully understood. Here, we systematically investigate the seed-mediated growth process of GNSs to gain an insight into the growth mechanism and evolution of their optical and photothermal properties. By tailoring the core size, tip length and tip angle, the main localized surface plasmon resonance (LSPR) peak wavelength can be broadly tuned from the visible to near-infrared (NIR) region. Our observations show that the protruding tips grow rapidly away from the central core at the initial growth stage, leading to a red-shift of the main LSPR peak. The preferential deposition of gold atoms onto the gold core takes place at the later growth stage, gradually blue-shifting the main LSPR peak. GNSs exhibit a large molar extinction coefficient ranging from 4.0 × 108 M–1 cm–1 to 4.5 × 1010 M–1 cm–1, the log value of which correlates linearly with the main LSPR peak wavelength and accordingly allows for facile determination of the GNS concentration in a suspension. In addition, GNSs are excellent NIR photothermal materials with the LSPR-dependent photothermal conversion efficiency. The maximum photothermal conversion efficiency of GNSs occurs at a LSPR wavelength of 740 nm, blue-shifted from the incident laser wavelength. Our present work suggests that GNSs exhibit excellent optical and photothermal properties that can be optimized by tailoring the dimensional parameters

Novel insights into the mechanisms by which lncRNA HOTAIR regulates migration and invasion in HeLa cells

HOTAIR, as one of the few well-studied oncogenic lncRNAs, is involved in human tumorigenesis and is dys-regulated in most human cancers. The transcription co-activator factor YAP1 is broadly expressed in many tissues, and promotes cancer metastasis and progression. However, the precise biological roles of HOTAIR and YAP1 in cancer cells remain unclear. In this study, we showed that HOTAIR regulates H3K27 histone modification in the promoter of miR-200a to mediate miR-200a expression by recruiting EZH2. YAP1, as a potential target gene of miR-200a, aggravated the effects of miR-200a on the migration and invasion of HeLa cells. YAP1 activated the transcription of RPL23, which is a novel downstream transcriptional-regulator of YAP1. Agreement with this, the expression of YAP1 and RPL23 was dramatically decreased after injecting HeLa cells transfected with siHOTAIR in a xenograft mouse model. Accordingly, we propose a novel model of the molecular mechanism by which HOTAIR promotes the migration and invasion of cancer cells involving the miR-200a-3p/YAP1/RPL23 axis.</p

Enzymatic Protein–Protein Conjugation through Internal Site Verified at the Single-Molecule Level

Enzymes are widely used for protein ligation because of their efficient and site-specific connections under mild conditions. However, many enzymatic ligations are restricted to connections between protein termini while protein–protein conjugation at a specific internal site is limited. Previous work has found that Sortase A (SrtA) conjugates small molecules/peptides to a pilin protein at an internal lysine site via an isopeptide bond. Herein, we apply this noncanonical ligation property of SrtA for protein–protein conjugation at a designed YPKH site. Both a small protein domain, I27, and a large protein, GFP, were ligated at the designed internal site. Moreover, besides characterization by classic methods at the ensemble level, the specific ligation site at the interior YPKH motif is unambiguously verified by atomic force microscopy-based single-molecule force spectroscopy, showing the characteristic unfolding signature at the single-molecule level. Finally, steered molecular dynamics simulations also agreed with the results

Fullerene Transformed into a 3‑D Structure of Nitrogen-Doped Few-Layer Graphene Sheets: Growth and Field Emission Properties

3-D-structured nitrogen-doped few-layer graphene sheets (3-D NFLGs) have been prepared using a fullerene C60 precursor combined with a microwave excited nitrogen plasma process. A deep understanding of the growth mechanism and regulating of morphology that can adjust the field emission properties is crucial for its widespread application. In this work, the detailed growth process and microstructure and the field emission properties of the as-synthesized vertical aligned 3-D NFLGs were studied. The growth of the 3-D NFLGs can be divided into three steps: evaporation of the C60, opening of the C60, and formation of the 3-D NFLGs. The growth process and morphology of the materials can be neatly regulated by changing the evaporating temperature of the C60, electron temperature of the plasma, and substrate temperature through our self-designed reaction equipment. Interestingly, the vertical 3-D NFLGs grew at a limited microwave power and nitrogen pressure and could be divided into three different morphological features, reflected in their distribution uniformity, interparietal distance, number of layers, and crystallinity, which exhibited different field emission properties. Additionally, the 3-D NFLGs were all in situ doped with ∼4% nitrogen atoms from nitrogen gas during the growth process, while different compositions of the nitrogen atoms were reflected in the graphitic N increasing with increasing nitrogen pressure. Furthermore, the field emission measurements show that the as-obtained vertical 3-D NFLGs exhibited the lowest turn-on electric field (1.30 V/μm@10 μA/cm2) and threshold field (2.1 V/μm@1 mA/cm2) at the M1 morphology and the highest stability at the M3 morphology. Remarkable field emission performance was obtained for the 3-D NFLGs with M2 morphology, showing their great potential for field emission applications