Fluorescent Ensemble Based on Bispyrene Fluorophore and Surfactant Assemblies: Sensing and Discriminating Proteins in Aqueous Solution

A particular bispyrene fluorophore (<b>1</b>) with two pyrene moieties covalently linked via a hydrophilic spacer was synthesized. Fluorescence measurements reveal that the fluorescence emission of <b>1</b> could be well modulated by a cationic surfactant, dodecyltrimethylammonium bromide (DTAB). Protein sensing studies illustrate that the selected ensemble based on <b>1</b>/DTAB assemblies exhibits ratiometric responses to nonmetalloproteins and turn-off responses to metalloproteins, which can be used to differentiate the two types of proteins. Moreover, negatively charged nonmetalloproteins can be discriminated from the positively charged ones according to the difference in ratiometric responses. Fluorescence sensing studies with control bispyrenes indicate that the polarity of the spacer connecting two pyrene moieties plays an important role in locating bispyrene fluorophore in DTAB assemblies, which further influences its sensing behaviors to noncovalent interacting proteins. This study sheds light on the influence of the probe structure on the sensing performance of a fluorescent ensemble based on probe and surfactant assemblies

Discrimination of Metalloproteins by a Mini Sensor Array Based on Bispyrene Fluorophore/Surfactant Aggregate Ensembles

Fluorescent sensor arrays with pattern recognition ability have been widely used to detect and identify multiple chemically similar analytes. In the present work, two particular bispyrene fluorophores containing hydrophilic oligo­(oxyethylene) spacer, <b>6</b> and <b>4</b>, were synthesized, but one is with and the other is without cholesterol unit. Their ensembles with cationic surfactant (CTAB) assemblies realize multiple fluorescence responses to different metalloproteins, including hemoglobin, myoglobin, ferritin, cytochrome <i>c</i>, and alcohol dehydrogenase. The combination of fluorescence variation at monomer and excimer emission of the two binary sensor ensembles enables the mini sensor array to provide a specific fingerprint pattern to each metalloprotein. Linear discriminant analysis shows that the two-ensemble-sensor-based array could well discriminate the five tested metalloproteins. The present work realizes using a mini sensor array to accomplish discrimination of complex analytes like proteins. They also display a very high sensitivity to the tested metalloproteins with detection limits in the range of picomolar concentration

Fluorescent Binary Ensemble Based on Pyrene Derivative and Sodium Dodecyl Sulfate Assemblies as a Chemical Tongue for Discriminating Metal Ions and Brand Water

Enormous effort has been put to the detection and recognition of various heavy metal ions due to their involvement in serious environmental pollution and many major diseases. The present work has developed a single fluorescent sensor ensemble that can distinguish and identify a variety of heavy metal ions. A pyrene-based fluorophore (<b>PB</b>) containing a metal ion receptor group was specially designed and synthesized. Anionic surfactant sodium dodecyl sulfate (SDS) assemblies can effectively adjust its fluorescence behavior. The selected binary ensemble based on <b>PB</b>/SDS assemblies can exhibit multiple emission bands and provide wavelength-based cross-reactive responses to a series of metal ions to realize pattern recognition ability. The combination of surfactant assembly modulation and the receptor for metal ions empowers the present sensor ensemble with strong discrimination power, which could well differentiate 13 metal ions, including Cu²⁺, Co²⁺, Ni²⁺, Cr³⁺, Hg²⁺, Fe³⁺, Zn²⁺, Cd²⁺, Al³⁺, Pb²⁺, Ca²⁺, Mg²⁺, and Ba²⁺. Moreover, this single sensing ensemble could be further applied for identifying different brands of drinking water

Ternary System Based on Fluorophore–Surfactant AssembliesCu²⁺ for Highly Sensitive and Selective Detection of Arginine in Aqueous Solution

A new cationic dansyl derivative-based (DIlSD) fluorescence probe was designed and synthesized. Its combination with anionic surfactant SDS assemblies shows enhanced fluorescence intensity and blue-shifted maximum wavelength. Its fluorescence can be slightly quenched by Cu²⁺; however, the fluorescence quenching efficiency by Cu²⁺ is highly increased upon titration of arginine (Arg). As a result, the ternary system containing the cationic fluorophore, anionic surfactant, and Cu²⁺ functions as a highly sensitive and selective sensor to Arg. The optimized sensor system displays a detection limit of 170 nM, representing the highest sensitivity to Arg in total aqueous solution by a fluorescent sensor. Control experiments reveal that the imidazolium groups in the fluorophore, the anionic surfactant, and Cu²⁺ all play important roles in the process of sensing Arg. The electrostatic interaction between the cationic fluorophore and anionic surfactants facilitates the binding of imidazolium rings with Cu²⁺, the surfactant surface-anchored Cu²⁺ is responsible for further binding of Arg, and the electrostatic interaction between anionic surfactants and positively charged amino acids accounts for the selective responses to Arg

Sectioning of stem segments from 2-month-old white poplar trees.

<p>Four stem segments were collected at the following points: 1 cm below the apical meristem and at LPI 4, 5, and 9, respectively. Hand-made transverse sections were stained with 0.05% Toluidine Blue-O. A, E: The stem segment 1 cm below the apical meristem, showing the primary xylem (px) and primary phloem tissues (pp) from procambial cells; B, F: The stem segment LPI 4 with formation of secondary vascular cambium ring (vc), xylem interfascicular fiber (if) and wall–thickened phloem fiber (pf); C, G: The stem segment LPI 5, where secondary xylem grew rapidly with the concurrence of xylem fiber cells (xf); D, H: The stem segment LPI 9 with abundant secondary xylem, including xylem vessel (xv), xylem fiber (xf), ray (r), and pith (p).</p

Validation of candidate reference genes by geNorm.

<p>A) Average expression stability values of remaining control genes plotted from least stable (left) to most stable (right). The average expression stability values were calculated for the remaining control genes after the least stable gene with the highest <i>M</i> value was excluded from the new calculation round. B) Pairwise variation (V) analysis to determine the optimal number of reference genes. The pairwise variation V_n/n+1 was calculated between two sequential normalization factors NF_n and NF_n+1.</p

Control genes ranked in order of their expression stability by geNorm, NormFinder and BestKeeper^*.

<p>Control genes ranked in order of their expression stability by geNorm, NormFinder and BestKeeper^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157370#t003fn001" target="_blank">*</a>}.</p

Micelle-Induced Versatile Sensing Behavior of Bispyrene-Based Fluorescent Molecular Sensor for Picric Acid and PYX Explosives

The effect of surfactant micelles on the photophysical properties of a cationic bispyrene fluorophore, Py-diIM-Py, was systemically examined. The results from series of measurements including UV–vis absorption, steady-state fluorescence emission, quantum yield, fluorescence lifetime, and time-resolved emission spectra reveal that the cationic fluorophore is only encapsulated by the anionic sodium dodecyl sulfate (SDS) surfactant micelles and not incorporated in the cationic dodecyltrimethylammonium bromide (DTAB) and neutral Triton X-100 (TX100) surfactant micelles. This different fluorophore location in the micellar solutions significantly influences its sensing behavior to various explosives. Fluorescence quenching studies reveal that the simple variation of micellar systems leads to significant changes in the sensitivity and selectivity of the fluorescent sensor to explosives. The sensor exhibits an on–off response to multiple explosives with the highest sensitivity to picric acid (PA) in the anionic SDS micelles. In the cationic DTAB micelles, it displays the highest on–off responses to PYX. Both the sensitivity and selectivity to PYX in the cationic micelles are enhanced compared with that to PA in the anionic micelles. However, the poor encapsulation in the neutral surfactant TX100 micelles leads to fluorescence instability of the fluorophore and fails to function as a sensor system. Time-resolved fluorescence decays in the presence of explosives reveal that the quenching mechanism of two micellar sensor systems to explosives is static in nature. The present work demonstrates that the electrostatic interaction between the cationic fluorophore and differently charged micelles plays a determinative role in adjusting its distribution in micellar solutions, which further influences the sensing behavior of the obtained micellar sensor systems

Specificity of qRT-PCR amplification.

<p>Melting curves of the 8 amplicons (<i>18S</i>, <i>ACT6</i>, <i>EF1-beta</i>, <i>eIF5A</i>, <i>HIS3</i>, <i>RP</i>, <i>TUBB</i>, <i>UBQ</i>), all showing single peak.</p

Protein Binding-Induced Surfactant Aggregation Variation: A New Strategy of Developing Fluorescent Aqueous Sensor for Proteins

Novel strategies of developing fluorescent sensors for proteins are highly demanded. In this work, we particularly synthesized a cholesterol-derivatized pyrene probe. Its fluorescence emission is effectively tuned by the aggregation state of a cationic surfactant dodecyltrimethylammonium bromide (DTAB). The used probe/DTAB assemblies exhibit highly sensitive ratiometric responses to pepsin and ovalbumin egg (o-egg) with detection limits of 4.8 and 18.9 nM, respectively. The fluorescence changes indicate the protein–surfactant interaction leads to further aggregation of DTAB assemblies. The results from Tyndall effect and dynamic light scattering verify this assumption. The responses to pepsin and o-egg are due to their strong electrostatic or hydrophobic interaction with DTAB assemblies at pH 7.4. The present noncovalent supramolecular sensor represents a novel and simple strategy for sensing proteins, which is based on the encapsulated fluorophore probing the aggregation variation of the surfactant assemblies