Search

Contamination of water supplies by polyfluoroalkyl substances, notably perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), has serious health and environmental consequences. Therefore, the development of straightforward and effective means of monitoring and removing PFASs is urgently required. In this study, we report a rapid and sensitive method for the detection of PFOS and PFOA in water that rely on the J‐aggregate formation of meso‐ester‐BODIPY dyes. The dye C10‐mim, which contains a hydrophilic methylimidazolium group and a hydrophobic alkylated BODIPY, self‐assembles in water into weakly green‐emissive micellar assemblies. Upon binding to PFOS or PFOA, a spontaneous disassembly and reorganization forms orange‐emissive J‐aggregates. The rapid formation (≤5 s) of J‐aggregates and the accompanying spectral shifts provide a superior sensing performance, with excellent sensitivity (limit of detection=0.18 ppb for PFOS) and distinct chromogenic and fluorogenic "turn‐on" responses. [ABSTRACT FROM AUTHOR]

Urokinase‐type plasminogen activator receptor (uPAR) is a glycolipid‐anchored protein located on the cell surface that is implicated in the promotion of metastasis. New fluorescent probes for the detection of uPAR expression that feature a rapid "turn‐on" response are reported here. They consist of a donor‐π‐acceptor‐based fluorophore conjugated with a uPAR‐binding AE105 peptide. The resulting AE105‐coupled uPAR‐targeting probes are weakly emissive in aqueous buffer solutions; however, a fluorescence "turn‐on" signal is instantly triggered upon specific binding to uPAR (KD=63.2 nM for P1 and 49.5 nM for P2), which restricts the rotational deactivation of the fluorophore. Applications of the probes were demonstrated in the imaging of uPAR overexpressed on the membrane of cancer cell and in a cell‐based uPAR inhibitor assay. [ABSTRACT FROM AUTHOR]

Designing a web panel for composite girders necessitates an accurate evaluation of the shear buckling strength. However, the current design specifications calculate the strength of web panels for composite girders conservatively. Additionally, its rational determination is missing in existing studies. This study investigates the shear buckling coefficients of composite girders through numerical analysis. The numerical analysis model assumes that the concrete slab fully restrains the web panel. In addition, the concrete slab of the composite girders in the numerical analysis model is replaced by equivalent top flange sections using a transformed thickness according to the modular ratio (n) of the concrete and steel. Additionally, the stiffness of the bottom flange and web panel is parameterized to evaluate the effect of their relative stiffness on the critical shear buckling strength of the web panel. The results show that the relative stiffness of the flange and web panel significantly affects the shear buckling coefficient. To determine the shear buckling coefficient by reflecting these structural characteristics, the relative stiffness is defined as the ratio of the torsional stiffness of the flange to the flexural stiffness of the web panel. The proposed formulas for the shear buckling coefficient of web panels for composite girders correlate well with the numerical analysis results. Since the accurate shear buckling strength can be derived from these formulas, the web panel for composite girders can be designed more accurately and economically. • Local buckling behavior of webs in composite plate girders was investigated based on finite element analysis. • Effects of flange and web stiffness ratio on web shear buckling in composite plate girders was evaluated. • Improved design equations of shear buckling coefficients in web shear buckling were proposed. • The proposed design equations shows a good correlation with FEA results when compared with equations in literature. [ABSTRACT FROM AUTHOR]

Widespread abuse of amphetamine-type stimulants (ATS) calls for the development of reliable and rapid on-site analytical methods for their detection and quantitation. A simple, rapid, sensitive, selective, and inexpensive method for the colorimetric detection of ATS using furylidene Meldrum's acid derivative 1 is reported herein. This colorimetric assay is based on the formation of Stenhouse adducts, through a chromogenic ring-opening mechanism upon the reaction of 1 with secondary amines, including methamphetamine (METH), 3,4-methylenedioxymethamphetamine (MDMA), and related illicit drugs. The reaction is accompanied by the formation of a new, red shifted absorption band resulting in a distinct color change from colorless to red. The utility of the colorimetric assay is demonstrated in aqueous solution, spiked drinks, and 'ecstasy' tablets. Detection limits of 0.36 μg·mL−1 METH and 0.57 μg·mL−1 MDMA in aqueous solution are achieved, and the naked-eye detection of ATS is also realized within 5 min in multiple matrices. Moreover, this method is resistant to interference from various pharmaceuticals, controlled substances, or common cutting agents found in illicit drugs. Paper-based portable indicators based on 1 , suitable detection of ATS by agents in the field, are additionally reported. [Display omitted] • A simple colorimetric detection method for amphetamine-type stimulants (ATS) based on furylidene Meldrum's acid 1 is developed. • The assay features a fast response (< 5 min), operational simplicity, sensitive detection of drugs of abuse (LOD = 0.36 μg·mL−1 for METH and 0.57 μg·mL−1 for MDMA), and high-contrast color response. • The assay is robust against interferences, and compatible with matrices ranging from spiked beverages and urine samples to drug tablets. • The assay can be carried out not only in solution but also on a paper-based test strip platform, and it can be utilized for rapid presumptive color tests. [ABSTRACT FROM AUTHOR]

We report that the electrostatic association between a cyanovinylene (CV)-based cationic dye (CV–N+) and anionic surfactants rapidly induced the formation of self-assembled aggregates of CV-N+ molecules in an aqueous solution, displaying a red-shifted (Δλ = 100 nm), broad excimer emission at 650 nm. The anionic-surfactant-mediated excimer-forming properties of CV-N+ were further exploited as a versatile platform for the design of simple fluorescent "light-up" sensing systems for the specific and efficient detection of enzymatic activity (i.e., phospholipase D) and small molecules (i.e., bisulfite ions), respectively, without the complicated functionalization of fluorophores with suitable recognition groups. In these systems, which can be ensembled using various substrates, the cationic CV-N+ dye interacts with an anionic surfactant, which is the product of an analyte-induced specific reaction, thus triggering the formation of emissive aggregates. [ABSTRACT FROM AUTHOR]

meso‐Carboxyl‐BODIPY responds to small electronic changes resulting from acyl substitution reactions with a marked change in fluorescence. Herein, the minute changes that accompany the thioester to amide conversion encountered in native chemical ligation (NCL) are exploited in the construction of fluorescent "turn‐on" probes. Two fluorogenic probes, 1 a and 4, derived from a meso‐thioester‐BODIPY scaffold, were designed for the selective detection of cysteine (1 a) and aminopeptidase N (4), respectively. The aromatic (1 a) and aliphatic (4) thioesters of meso‐carboxyl‐BODIPY are nonfluorescent. However, specific analyte‐induced conversion to the meso‐amide derivative caused significant spectral changes and a dramatic fluorescence enhancement. Probe 1 a exhibited a large fluorescence "turn‐on" response with high selectivity toward cysteine via a tandem NCL reaction. Probe 4 was successfully applied to the monitoring and imaging of endogenous aminopeptidase N in live cancer cells. [ABSTRACT FROM AUTHOR]