Worldwide outbreaks of infectious diseases necessitate the development of rapid and accurate diagnostic methods. Colorimetric assays are a representative tool to simply identify the target molecules in specimens through color changes of an indicator (e.g., nanosized metallic particle, and dye molecules). The detection method is used to confirm the presence of biomarkers visually and measure absorbance of the colored compounds at a specific wavelength. In this study, we propose a colorimetric assay based on an extended form of double-stranded DNA (dsDNA) self-assembly shielded gold nanoparticles (AuNPs) under positive electrolyte (e.g., 0.1 M MgCl 2 ) for detection of Middle East respiratory syndrome coronavirus (MERS-CoV). This platform is able to verify the existence of viral molecules through a localized surface plasmon resonance (LSPR) shift and color changes of AuNPs in the UV−vis wavelength range. We designed a pair of thiol-modified probes at either the 5′ end or 3′ end to organize complementary base pairs with upstream of the E protein gene (upE) and open reading frames (ORF) 1a on MERS-CoV. The dsDNA of the target and probes forms a disulfide-induced long self-assembled complex, which protects AuNPs from salt-induced aggregation and transition of optical properties. This colorimetric assay could discriminate down to 1 pmol/μL of 30 bp MERS-CoV and further be adapted for convenient on-site detection of other infectious diseases, especially in resource-limited settings.

Highlights Aggressive responses to COVID-19 were successful in controlling an initial peak Korea's government reformed the epidemic preparedness system after MERS in 2015. Expanding rapid tests, case tracking/isolation, and information sharing were key. Hospitals set up selective clinics and safe clinics outside for patient screening. Hospitals modified personal protective equipment use and health care personnel report related symptoms daily.

Free radicals and reactive oxygen species (ROS) caused by UV exposure or other environmental factors are critical players in cellular damage and aging. In order to develop a new anti-photoaging agent, this work focused on the antioxidant effects of the extract of tinged autumnal leaves of Acer palmatum. One compound was isolated from an ethyl acetate soluble fraction of the A. palmatum extract using silica gel column chromatography. The chemical structure was identified as apigenin-8-C-beta-D-glucopyranoside, more commonly known as vitexin, by spectral analysis including LC-MS, FT-IR, UV, 1H-, and 13C-NMR. The biological activities of vitexin were investigated for the potential application of its anti-aging effects in the cosmetic field. Vitexin inhibited superoxide radicals by about 70% at a concentration of 100 microg/mL and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals by about 60% at a concentration of 100 microg/mL. Intracellular ROS scavenging activity was indicated by increases in dichlorofluorescein (DCF) fluorescence upon exposure to UVB 20 mJ/cm2 in cultured human dermal fibroblasts (HDFs) after the treatment of vitexin. The results show that oxidation of 5-(6-)chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-H2DCFDA) is inhibited by vitexin effectively and that vitexin has a potent free radical scavenging activity in UVB-irradiated HDFs. In ROS imaging using a confocal microscope we visualized DCF fluorescence in HDFs directly. In conclusion, our findings suggest that vitexin can be effectively used for the prevention of UV-induced adverse skin reactions such as free radical production and skin cell damage.

p21-activated kinase 4 (PAK4) regulates a wide range of cellular events, including cytoskeletal remodeling, cell growth, and survival. Our previous study identified PAK4 as a key regulator of cAMP-response element-binding protein (CREB) that acts upstream of microphthalmia-associated transcription factor (MITF), a master transcription factor in melanogenesis. We therefore investigated the role of PAK4 in melanogenesis. Melanocytes express both PAK2 and PAK4 isoforms, but only RNA interference knockdown of PAK4 significantly influenced α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis in B16 melanoma cells. Consistent with this result, PAK4 inhibition by PF3758309, a potent ATP-competitive inhibitor of PAKs, suppressed not only α-MSH-induced melanogenesis in B16 melanoma and human epithelial melanocyte cells but also UVB-induced melanogenesis in the skin of melanin-possessing hairless mice (HRM-2) in a dose-dependent manner. Inhibition of PAK4 over several days markedly decreased the levels of CREB, MITF, and tyrosinase in both HRM-2 mice and B16 melanoma cells. Moreover, PAK4 knockdown and inhibition suppressed α-MSH-stimulated β-catenin phosphorylation at serine 675 (S675) but enhanced phosphorylation at S33/37, an indicator for ubiquitination-dependent proteolysis. Together, our results provide evidence that PAK4 promotes α-MSH/UVB-induced melanogenesis via the CREB and Wnt/β-catenin signaling pathways and suggest that PAK4 may be a potential therapeutic target in pigmentation disorders.

A comprehensive experimental and theoretical study of the reactivity patterns and reaction mechanisms in alkane hydroxylation, olefin epoxidation, cyclohexene oxidation, and sulfoxidation reactions by a mononuclear nonheme ruthenium(IV)-oxo complex, [Ru(IV)(O)(terpy)(bpm)](2+) (1), has been conducted. In alkane hydroxylation (i.e., oxygen rebound vs oxygen non-rebound mechanisms), both the experimental and theoretical results show that the substrate radical formed via a rate-determining H atom abstraction of alkanes by 1 prefers dissociation over oxygen rebound and desaturation processes. In the oxidation of olefins by 1, the observations of a kinetic isotope effect (KIE) value of 1 and styrene oxide formation lead us to conclude that an epoxidation reaction via oxygen atom transfer (OAT) from the Ru(IV)O complex to the C═C double bond is the dominant pathway. Density functional theory (DFT) calculations show that the epoxidation reaction is a two-step, two-spin-state process. In contrast, the oxidation of cyclohexene by 1 affords products derived from allylic C-H bond oxidation, with a high KIE value of 38(3). The preference for H atom abstraction over C═C double bond epoxidation in the oxidation of cyclohexene by 1 is elucidated by DFT calculations, which show that the energy barrier for C-H activation is 4.5 kcal mol(-1) lower than the energy barrier for epoxidation. In the oxidation of sulfides, sulfoxidation by the electrophilic Ru-oxo group of 1 occurs via a direct OAT mechanism, and DFT calculations show that this is a two-spin-state reaction in which the transition state is the lowest in the S = 0 state.