Alkynyl-protected Ag20 Rh2 Nanocluster with Atomic Precision: Structure Analysis and Tri-functionality Catalytic Application

We report the overall structure and trifunctionality catalytic application of an atomically precise alloy nanocluster of Ag20 Rh2 (C≡C-t Bu)16 (CF3 CO2 )6 (H2 O)2 (abbreviated as Ag20 Rh2 hereafter). Ag20 Rh2 has a twisted rod-like structure, where a Ag4 @Rh2 kernel is connected by two twisted Ag8 cubes on two sides. Ag20 Rh2 is a superatomic cluster with four free valence electrons, and it has characteristic absorbance feature. Interestingly, Ag20 Rh2 exhibited superior catalytic performance than the larger AgRh nanoparticle counterparts in electrochemical hydrogen evolution reaction (HER), reduction of 4-nitrophenol, and the methyl orange degradation reaction. Such intriguing catalytic properties are attributed to the more exposed active sites from the ultrasmall nanoclusters than relatively large nanoparticles. This study not only enriches the family member of alkynyl-protected AgRh nanoclusters with atomic precision, but also highlights the great advantages of employing nanoclusters as efficient catalysts for multiple functionalities.

Cip2a induces arginine biosynthesis and promotes tumor progression in non-small cell lung cancer

Cancerous inhibitor of protein phosphatase 2A (Cip2a) is an oncoprotein, playing important roles in tumor progression. However, the underlying mechanisms by which Cip2a promotes tumor aggressiveness in NSCLC remain to be further investigated. In this study, we found that Cip2a expression is elevated in NSCLC and correlates with poor prognosis. Knockdown of Cip2a significantly reduced the ability of cell proliferation, invasion, and metastasis of NSCLC both in vitro and in vivo. Furthermore, we found that Cip2a promotes tumor progression partly by inducing arginine biosynthesis, and knockdown of Cip2a exhibited a significantly increased sensitivity to arginine deprivation and mTOR inhibition. In addition, we found that p53 mutants in NSCLC cells increased Cip2a expression by inhibiting the activity of wild-type p53. Our findings provide new insights into the mechanisms of Cip2a in promoting tumor progression and suggest that Cip2a represents a potential therapeutic target for treating NSCLC.

CeO2-Based Two-Dimensional Layered Nanocomposites Derived from a Metal-Organic Framework for Selective Electrochemical Dopamine Sensors

In this work, we demonstrate the incorporation of two-dimensional (2D) layered materials into a metal-organic framework (MOF) derived from one-dimensional (1D) cerium oxide (CeO2) for the electrochemical detection of dopamine. Ce-MOF was employed as a sacrificial template for preparing CeO2 with 2D materials by the pyrolysis process. The influence of the pyrolysis temperature was studied to achieve a better crystal structure of CeO2. Siloxene improved the dopamine sensing performance of CeO2 compared with graphitic carbon nitride (g-C3N4) due to the basal plane surface oxygen and hydroxyl groups of 2D siloxene. Under optimal conditions, the fabricated CeO2/siloxene electrode exhibited a detection limit of 0.292 μM, with a linear range from 0.292 μM to 7.8 μM. This work provides a novel scheme for designing the CeO2 material with siloxene for excellent dopamine sensors, which could be extended towards other biosensing applications.

Binding interaction of sodium benzoate food additive with bovine serum albumin: multi-spectroscopy and molecular docking studies

Sodium benzoate (SB) is widely used as a preservative in food industry, and bovine serum albumin (BSA) is a major carrier protein similar to human serum albumin (HSA), the study of the binding between the two has great significance on human health. In this paper, we systematically investigated the binding of SB and BSA under the simulated physiological conditions combining with various common analytical methods, e.g., fluorescence, UV-vis absorption, synchronous fluorescence and circular dichroism (CD) spectra, as well as molecular docking method. The fluorescence quenching measurements were respectively carried out at 298 K, 303 K and 308 K using the Stern-Volmer method. The results reveal that ground state SB-BSA complex was formed within the binding constants from 2.02 × 104 to 7.9 × 103 M-1. Meanwhile, the negative values of ΔH 0 (- 43.92 kJ mol-1) and ΔS 0 (- 111.6 J mol-1 K-1) demonstrated that both the hydrogen binding interaction and van der Waals forces contributed to stabilizing the SB-BSA complex. The site marker competitive experiments show that the SB and BSA bound at site I. Furthermore, the experimental results of UV-vis absorption, synchronous fluorescence and CD spectra indicate that the binding of SB and BSA may change the conformation of BSA. In addition, the molecular docking experiment suggests that hydrogen bond was formed in the interaction between SB and BSA.

Conductance Changes in Bovine Serum Albumin Caused by Drug-Binding Triggered Structural Transitions

Proteins, due to their binding selectivity, are promising candidates for fabricating nanoscale bio-sensors. However, the influence of structural change on protein conductance caused by specific protein-ligand interactions and disease-induced degeneration still remains unknown. Here, we excavated the relationship between circular dichroism (CD) spectroscopy and conductive atomic force microscopy (CAFM) to reveal the effect of the protein secondary structures changes on conductance. The secondary structure of bovine serum albumin (BSA) was altered by the binding of drugs, like amoxicillin (Amox), cephalexin (Cefa), and azithromycin (Azit). The CD spectroscopy shows that the α-helical and β-sheet content of BSA, which varied according to the molar ratio between the drug and BSA, changed by up to 6%. The conductance of BSA monolayers in varying drug concentrations was further characterized via CAFM. We found that BSA conductance has a monotonic relation with α-helical content. Moreover, BSA conductance seems to be in connection with the binding ability of drugs and proteins. This work elucidates that protein conductance variations caused by secondary structure transitions are triggered by drug-binding and indicate that electrical methods are of potential application in protein secondary structure analysis.

Enhanced electrochemical properties of cerium metal-organic framework based composite electrodes for high-performance supercapacitor application

Cerium metal-organic framework based composites (Ce-MOF/GO and Ce-MOF/CNT) were synthesized by a wet chemical route and characterized with different techniques to characterize their crystal nature, morphology, functional groups, and porosity. The obtained Ce-MOF in the composites exhibit a nanorod structure with a size of ∼150 nm. The electrochemical performance of the composites was investigated in 3 M KOH and 3 M KOH + 0.2 M K3Fe(CN)6 electrolytes. Enhanced electrochemical behavior was obtained for the Ce-MOF/GO composite in both electrolytes and exhibited a maximum specific capacitance of 2221.2 F g-1 with an energy density of 111.05 W h kg-1 at a current density of 1 A g-1. The large mesoporous structure and the presence of oxygen functional groups in Ce-MOF/GO could facilitate ion transport in the electrode/electrolyte interface, and the results suggested that the Ce-MOF/GO composite could be used as a high-performance supercapacitor electrode material.