Pattern Of Fluorescence Changes Research Articles

Kaleidoscopic fluorescent arrays for machine-learning-based point-of-care chemical sensing

Multiplexed analysis allows simultaneous measurements of multiple targets, improving the detection sensitivity and accuracy. However, highly multiplexed analysis has been challenging for point-of-care (POC) sensing, which requires a simple, portable, robust, and affordable detection system. In this work, we developed paper-based POC sensing arrays consisting of kaleidoscopic fluorescent compounds. Using an indolizine structure as a fluorescent core skeleton, named Kaleidolizine (KIz), a library of 75 different fluorescent KIz derivatives were designed and synthesized. These KIz derivatives are simultaneously excited by a single ultraviolet (UV) light source and emit diverse fluorescence colors and intensities. For multiplexed POC sensing system, fluorescent compounds array on cellulose paper was prepared and the pattern of fluorescence changes of KIz on array were specific to target chemicals adsorbed on that paper. Furthermore, we developed a machine-learning algorithm for automated, rapid analysis of color and intensity changes of individual sensing arrays. We showed that the paper sensor arrays could differentiate 35 different volatile organic compounds using a smartphone-based handheld detection system. Powered by the custom-developed machine-learning algorithm, we achieved the detection accuracy of 97 % in the VOC detection. The highly multiplexed paper sensor could have favorable applications for monitoring a broad-range of environmental toxins, heavy metals, explosives, pathogens.

A novel detector using a fluorescent sensor array and discrimination of pesticides

A novel, simple, and rapid detector using a fluorescent sensor array for discrimination and quantification of different concentrations (ppb level) of pesticides was proposed in this paper. Employing porphyrin, porphyrin derivatives, and chemically responsive dyes as the sensing elements, the developed sensor array based on a cross-responsive mechanism showed a unique pattern of fluorescence changes upon the reaction that lasted just 10 min. The eigenvalues from raw fluorescence spectra were analyzed via a pattern recognition algorithm, including hierarchical cluster analysis (HCA), principal component analysis (PCA), and back-propagation neural network (BPNN). The results showed that HCA, which were used to assess the feasibility and effectiveness of discrimination of the fluorescent sensor array, revealed a distinct separation between different pesticides. PCA and BPNN were used for automatically predicting the concentration of pesticides, and the recovery was 91.29–109.81 % while the lowest relative standard deviation was up to 3.12 %. It indicates a detector based on the fluorescent sensor array is a rapid and feasible sensing platform for the discrimination and quantitative analysis of pesticides, and also shows the possibilities in the related fields of pesticides identification and detection.

Detection of ammonia based on a novel fluorescent artificial nose and pattern recognition

A simple and rapid fluorescent sensor array for identification and quantification of different concentrations (ppb level) of ammonia was proposed in this paper. Employing porphyrin, porphyrin derivative and chemically responsive dyes as the sensing elements, the developed sensor array of artificial nose showed a unique pattern of fluorescence changes upon its exposure to ammonia for just 4 min. And the eigenvalues from raw fluorescence spectra were analyzed by means of pattern recognition algorithm, including hierarchical cluster analysis (HCA), principal component analysis (PCA) and back-propagation neural network (BPNN). The results showed that HCA and PCA, which were used to assess the feasibility and effectiveness of discrimination of fluorescent sensor array, revealed a distinct separation between samples. BPNN were used for automatically classifying and predicting concentration of ammonia, and the accuracy was 97.55% while the relative standard deviation (RSD) was up to 3.67% for real samples. It indicates the fluorescent artificial nose system is a rapid and feasible sensing platform for the identification and quantitative analysis of gases, and also shows the possibilities in the field of environmental gas detection and environmental gas monitoring.

ACTIVATION OF ACID SPHINGOMYELINASE DRIVES LYSOSOMAL TRIFFICKING AND FUSION TO MEMBRANE IN CORONARY ENDOTHELIAL CELLS

Recent studies have demonstrated that activation of death receptor results in lysosomal fusion to cell membrane to form a lipid rafts (LRs) signaling platform. However, the driving forces are still unknown. The present study was designed to test a hypothesis that acid sphingomyelinase (ASMase) is firstly activated to produce ceramide, then drives lysosomal fusion and LRs clustering. We first performed confocal microscopy and fluorescence resonance energy transfer (FRET) detection in bovine coronary arterial endothelial cells (BCAECs) and found that FasL significantly led to colocalization of Lamp‐1 and CTX‐B, and their FRET efficiency increased from 5 to 19%. We also found a lysosome‐membrane fusion pattern of fluorescence changes induced by FasL which was blocked by siRNA of ASMase. Both activator and inducer of ASMase markedly increased colocalization of Lamp‐1 with CTX‐B and resulted in lysosome‐membrane fusion. However, the de novo synthesis of ceramide had no such effects. In isolated bovine coronary arteries, endothelium‐dependent vasodilation was impaired after ASMase had been activated, which could be reversed by lysosome functional inhibitor. It is concluded that ASMase activation precedes lysosomal fusion and LRs clustering and may serve as a driving force for lysosome trafficking and fusion to cell membrane in BCAECs. (Supported by NIH Grants HL‐57244, HL‐75316, and DK54927).

Local and Global Ligand-Induced Changes in the Structure of the GABAA Receptor

Ligand-gated channels mediate synaptic transmission through conformational transitions triggered by the binding of neurotransmitters. These transitions are well-defined in terms of ion conductance, but their structural basis is poorly understood. To probe these changes in structure, GABA(A) receptors were expressed in Xenopus oocytes and labeled at selected sites with environment-sensitive fluorophores. With labels at two different residues in the alpha1 subunit in loop E of the GABA-binding pocket, GABA elicited fluorescence changes opposite in sign. This pattern of fluorescence changes is consistent with a closure of the GABA-binding cavity at the subunit interface. The competitive antagonist SR-95531 inverted this pattern of fluorescence change, but the noncompetitive antagonist picrotoxin failed to elicit optical signals. In response to GABA (but not SR-95531), labels at the homologous residues in the beta2 subunit showed the same pattern of fluorescence change as the alpha1-subunit labels, indicating a global transition with comparable movements in homologous regions of different subunits. Incorporation of the gamma2 subunit altered the fluorescence changes of alpha1-subunit labels and eliminated them in beta2-subunit labels. Thus, the ligand-induced structural changes in the GABA(A) receptor can extend over considerable distances or remain highly localized, depending upon subunit composition and ligand.

The dynamic distribution and quantification of DNA cruciforms in eukaryotic nuclei

Cruciforms have been suggested as potential recognition structures at or near origins of DNA replication in eukaryotic cells. Monoclonal antibodies specific for cruciforms have been produced. The antibody binds to structural determinants at the base of the cruciform stem, the “elbow.” Labeling of nuclei with anti-cruciform antibodies produces a nonuniform pattern of fluorescence in cells arrested at the G 1 S boundary. This pattern of fluorescence changes when these cells are released from synchrony. Using fluorescence flow cytometry to quantify the number of DNA cruciform structures in cells throughout the cell cycle, we observed two major populations of nuclei with different numbers of cruciforms; the modal number of cruciforms in these populations was 0.6 × 10 5 and 3 × 10 5 cruciforms per nucleus. Synchronized cells (doubly arrested by serum starvation and aphidicolin) displayed a biphasic distribution of the number of cruciforms over the first 6 h after release from synchrony with maxima at 0 and 4 h after release.

Effects of the myeloperoxidase system on fluorescent probes of granulocyte membrane potential.

Activation of normal or myeloperoxidase-deficient human granulocytes by phorbol myristate acetate resulted in an initial membrane depolarization as indicated by an increase in fluorescence of the lipophilic cation probe of membrane potential, 3,3'-dipropylthiodicarbocyanine. A subsequent apparent hyperpolarization (decrease in fluorescence) was observed in normal but not myeloperoxidase-deficient cells. Addition of purified myeloperoxidase restored a normal pattern of fluorescence changes to the enzyme-deficient granulocytes. The secondary decrease in fluorescence in normal cells was markedly blunted by addition of azide, cyanide, or catalase. In a cell-free system, the fluorescence of 3,3'-dipropylthiodicarbocyanine, but not that of 3,3'-dipentyloxadicarbocyanine, was rapidly eliminated by myeloperoxidase in the presence of hydrogen peroxide and a halide; this loss of fluorescence was inhibited by azide, cyanide, or catalase. These findings indicate that secretion of myeloperoxidase and hydrogen peroxide by activated granulocytes results in decreased fluorescence of 3,3'-dipropylthiodicarbocyanine, probably by thioether oxidation. While the determination of initial rates of depolarization using this probe is unaffected by the myeloperoxidase system, measurement of extent of depolarization and any subsequent membrane potential changes requires the addition of inhibitors. In the absence of inhibitors, the secondary decrease in fluorescence can be used as an indicator of secretion of myeloperoxidase and hydrogen peroxide.