Determination of atenolol in human urine by emission-excitation fluorescence matrices and unfolded partial least-squares with residual bilinearization

A second-order multivariate calibration method based on a combination of unfolded partial least-squares (U-PLS) with residual bilinearization (RBL) has been applied to second-order data obtained from excitation-emission fluorescence matrices for determining atenolol in human urine, even in the presence of background interactions and fluorescence inner filter effects, which are both sample dependent. Atenolol is a cardioselective beta-blocker, which is considered a doping agent in shoot practice, so that its determination in urine can be required for monitoring the drug. Loss of trilinearity due to analyte-background interactions which may vary between samples, as well as inner filter effects, precludes the use of methods like parallel factor analysis (PARAFAC) that cannot handle trilinearity deviations, and justifies the employment of U-PLS. Successful analysis required to include the background in the calibration set. Unexpected components appear in new urine samples, different from those used in calibration set, requiring the second-order advantage which is obtained from a separate procedure known as residual bilinearization (RBL). Satisfactory results were obtained for artificially spiked urines, and also for real urine samples. They were statistically compared with those obtained applying a reference method based on high-performance liquid chromatography (HPLC).     

A new class of modular chiral ligands with fluxional groups

In ligand design for asymmetric catalysis, the usual norm is to derive the face shielding elements from a chiral source. New ligands in which the face shielding is determined by fluxional groups are introduced. Their design, modular synthesis, and experiments to demonstrate the significance of the fluxional groups are discussed. The advantage is that the fluxional groups, introduced at a later stage, allow for simple tuning of the face shielding group.     

Complete suppression of the fluorophore fluorescence by combined effect of multiple fluorescence quenching groups: A fluorescent sensor for Cu with zero background signals

The reaction-based fluorescent sensors have attracted increasing attention in the past decades. However, the application of these sensors for accurate sensing was significantly retarded by the background fluorescence from the sensors themselves. In this work, we demonstrated a novel strategy that the background fluorescence of the sensor could be completely eliminated by the combined effect of multiple fluorescence quenching groups. Based on this new strategy, as proof-of-principle study, a fluorescent sensor (CuFS) for Cu²⁺ was judiciously developed. In CuFS, three types of fluorescence quenching groups were directly tethered to a commonly used coumarin fluorophore. The fluorescence of coumarin fluorophore in CuFS was completely suppressed by the combined effect of these fluorescence quenching groups. Upon treatment with 22 μM Cu²⁺, sensor CuFS achieved a dramatic fluorescence enhancement (fluorescence intensity enhanced up to 811-fold) centered at 469 nm. The detection limits was determined to be 12.3 nM. The fluorescence intensity enhancement also showed a good linearity with the Cu²⁺ concentration in the range of 12.3 nM to 2 μM. By fabricating test strips, sensor CuFS can be utilized as a simple tool to detect Cu²⁺ in water samples. Furthermore, the fluorescent sensor was successfully applied in detecting different concentration of Cu²⁺ in living cells.     

A new modification of an old framework: Hofmann layers with unusual tetracyanidometallate groups

Cyanidometallate complexes are highly versatile building units for the generation of functional porous materials. Here we report five new pillared Hofmann layer compounds incorporating the tetracyanidometallates [MoO(CN)(4)](2-) and [MnN(CN)(4)](2-). These metalloligands, which are new to this class of materials, have been combined with divalent 1st-row transition metals to produce Hofmann layers that are linked into three-dimensional frameworks by ditopic bridging dipyridyls. We report the structures and anomalous thermal expansion properties of five new materials: [Mn(H(2)O)(bpy)(?){MoO(CN)(4)(bpy)(?)}]·2H(2)O (1), [Mn(H(2)O)(bpy)(?){MnN(CN)(4)(bpy)(?)}]·2H(2)O (2), [Fe(H(2)O)(bpy)(?){MnN(CN)(4)(bpy)(?)}]·2H(2)O (3), [Co(H(2)O)(bpy)(?){MnN(CN)(4)(bpy)(?)}]·2H(2)O (4) and [{Mn(H(2)O)(2)}(?){Mn(bpa)(2)}(?){MoO(CN)(4)(bpa)(?)}]·MeOH (5), (where bpy = 4,4'-bipyridine and bpa = 4,4'-bipyridylacetylene).     

A new diterpene with two polymorphic modifications from a marine alga

A new diterpene, β-dictalediol monoacetate ( ), has been isolated from a brown alga X-ray crystal structure studies of have revealed the existence of two polymorphic modifications: dimorph in a chair/boat/chair conformation, and dimorph in a chair/chair/chair conformation.     

A new turn-on fluorescence probe for Zn in aqueous solution and imaging application in living cells

We designed and synthesized a new pyrazoline-based turn-on fluorescence probe for Zn²⁺ by the reaction of chalcone and thiosemicarbazide. The structure of the probe was characterized by IR, NMR and HRMS spectroscopy. The probe (L) exhibits high selectivity and sensitivity for detecting Zn²⁺ in buffered EtOH/HEPES solution (EtOH/HEPES = 1/1, pH 7.2) with 80-fold fluorescence enhancement, which is superior to previous reports. Job’s plot analysis revealed 1:1 stoichiometry between probe L and Zn²⁺ ions. The association constant estimated by the Benesi–Hildebrand method and the detection limit were 3.92 × 10³ M⁻¹ and 5.2 × 10⁻⁷ M, respectively. A proposed binding mode was confirmed by ¹H NMR titration experiments and density functional theory (DFT) calculations. The probe is cell-permeable and stable at the physiological pH range in biological systems. Because of its fast response to Zn²⁺, the probe can monitor Zn²⁺ in living cells. Moreover, the selective binding of L and Zn²⁺ was reversible with the addition of EDTA in buffered EtOH/HEPES solution and Zn²⁺ could be imaged in SH-SY5Y neuron cells.     

A comparative study of LED-induced fluorescence and laser-induced fluorescence in SDS-CGE: application to the analysis of antibodies

LEDs present an alternative to lasers in LIF detection with CE, resulting in LED-induced fluorescence (LEDIF). LEDs are much less expensive, consume less energy and are more stable. In addition, LED light sources allow a greater range of wavelengths to better match the maximum wavelength for the fluorescence of the dye. Antibodies were largely studied in SDS capillary gel electrophoresis (SDS-CGE) and LIF detection with different dyes to label the proteins. In this work, our goal is to show that LEDs can advantageously replace lasers. We used 5-carboxytetramethylrhodamine succinimidyl ester (5-TAMRA.SE), 3-(2-furoyl)-quinoline-2 carboxaldehyde (FQ), and naphthalene-2,3-dialdehyde (NDA) to label IgG and we compared the LIF sensitivity with that obtained from LEDIF. We measured that the LOD values of LEDIF are identical to that obtained with the wavelength equivalent laser, and for 5-TAMRA.SE analysis, LOD values are about six times better than when the classical 488 nm laser was used.     

A new total antioxidant potential measurements using RP-HPLC assay with fluorescence detection

In this paper, an improved total antioxidant potential (TAP) estimation using high-performance liquid chromatographic (HPLC) assay with fluorometric detection has been described. The principle of this method is based on the hydroxyl radicals generated in the Fenton-like reaction and subsequently detected using hydroxyterephthalic acid (HTPA), which is a reaction product of hydroxyl radicals and terephthalic acid (TPA), working as a sensing compound. HTPA quantity in the samples was measured by fluorescence detector working at excitation and emission wavelengths equal to 312 and 428 nm, respectively. A number of key experimental conditions including the influence of the reaction (incubation) time on the surface areas of HTPA peaks, concentration of Fe(II) ions as well as the influence of concentration of TPA on the surface area of the chromatographic peak of HTPA were optimized to the characteristic feature of TAP measurements. The elaborated assay has been used to evaluate TAP values of selected low-molecular mass compounds like pyrogallol, tryptamine, and n-alcohols (methanol, ethanol, and n-propanol) as well as chlorogenic and ascorbic acids and benzoic acid derivatives, which are commonly present in the food samples.     

A new fluorescent derivatization reagent and its application to free fatty acid analysis in pomegranate samples using HPLC with fluorescence detection

A new fluorescent labeling reagent has been developed for the determination of fatty acids (FAs) by HPLC with fluorescence detection. The derivatization conditions including the amount of derivatization reagent, temperature, and type of catalyst were investigated, the results indicated that the reaction proceeded within 30 min at 90°C in the presence of K₂CO₃ catalyst. The maximal yield was obtained with a four‐ to fivefold molar reagent excess. The derivatives exhibited strong fluorescence with an excitation maximum at λ_ex = 245 nm and an emission maximum at λ_em = 410 nm. Twenty‐five FA derivatives were well separated by RP‐HPLC on a Hypersil BDS C₈ column in combination with gradient elution. All FAs were found to give excellent linear responses with correlation coefficients >0.9992. The method gave a low LOQ of 0.85–5.5 ng/mL (S/N of 10). The developed method was employed to analyze free FAs (FFAs) composition in pomegranate samples without any purification. FFAs in samples were doubly identified by HPLC retention time and protonated molecular ion corresponding to m/z [M+H]⁺. This newly developed method allows a highly sensitive determination of trace FFAs from pomegranate and other foodstuffs.     

Dried biomass of green algae and its matrix matching with green parts of higher plants

Literature data for the content of matrix elements in dry biomass of green algae have been compared with those for green parts of higher plants. The data were evaluated by means of frequency histograms and box-and-whisker plots. With two exceptions (Fe, P), the spread of the data values for a given element was broader for higher plants than for algae. Distribution of the data was asymmetric, in most cases with long right-hand tails. All outliers found (average 5.6% for algae, 9.1% for higher plants) lay above the bulk of the data values. In all cases, there was either partial or (mostly) complete overlap of the ranges for algae with those for higher plants. While the question of matrix-matching of reference materials prepared from algal biomass with samples from green parts of higher plants can exhaustively be answered only after a similar comparison of the composition of matrix compounds, the content of the main matrix elements is certainly not doubtful.     

A new bio-based nanocomposite: fibrillated TEMPO-oxidized celluloses in hydroxypropylcellulose matrix

Utilization of TEMPO-oxidized celluloses in bio-based nanocomposites is reported for the first time. TEMPO-oxidized wood pulps (net carboxylate content 1.1 mmol/g cellulose) were fibrillated to varying degrees using a high intensity ultrasonic processor. The degree of fibrillation was controlled by varying sonication time from 1 to 20 min. The sonication products were then characterized independently and as fillers (5 wt% loading) in hydroxypropyl cellulose nanocomposite films. Nanofibril yields ranging from 11 to 98 wt% (on fiber weight basis) were obtained over the range of sonication times used. Suspension viscosities increased initially with sonication time, peaked with gel-like behavior at 10 min of sonication and then decreased with further sonication. The thermal degradation temperature of unfibrillated oxidized pulps was only minimally affected (6 °C decrease) by the fibrillation process. Dynamic mechanical analysis of the nanocomposites revealed strong fibril-matrix interactions as evidenced by remarkable storage modulus retention at high temperatures and a suppression of matrix glass transition at “high” (~5 wt%) nanofibril loadings. Creep properties likewise exhibited significant (order of magnitude) suppression of matrix flow at high temperatures. It was also believed, based on morphologies of freeze-fracture surfaces that the nanocomposites may be characterized by high fracture toughness. Direct fracture testing will however be necessary to verify this suspicion.     

Zeolites as host matrix for luminescent carbon dots:a new class of thermally activated delayed fluorescence materials with 350 ms delayed decay time

正Organic light-emitting diodes(OLEDs)have attracted considerable attentions from both academia and industry for decades because of their potential applications in full color flat-panel displays and solid state lightings.Since2009[1],thermally activated delayed fluorescence(TADF)OLEDs have drawn intense attention due to the utilization of low-cost organic luminogens by harvesting all singlet and triplet excitons to theoretically reach 100%internal     

Synthesis of new terpolymers with heterocyclic pendant groups

Chemical modifications of polyacrylonitrile (PAN), an inexpensive and commercial homopolymer, to obtain terpolymers containing 1,2,4 or 1,3,4 oxadiazolic pendant groups are described. These new materials are physically and spectroscopically characterized.     

A theoretical consideration of algae removal with clays

Recently, periodic and widespread algal blooms have been reported in the estuaries and lakes of Korea, causing a variety of problems for aquatic life and human activity. Currently, the only remedial practice employed for removing algal blooms is to spread clay on the surface of the water. However, the mechanism of algae removal is not well identified. In addition, engineering details and specifications for the correct selection of particle size, concentration of clay, spreading method and effective conditions have not been identified. In this study, the clay spreading practice has been investigated theoretically. A set of trajectory analyses was performed to calculate the collision efficiency of clay particles and algal cells. The sensitivity of the removal efficiency to the physical characteristics of both clay and algae was investigated. It was found that both particle/cell size and zeta potential of clay and algae are the most important parameters that control removal efficiency. Conclusions that might prove helpful to understand and guide clay spreading practice have been made. Selection of the appropriate particle size of clay in relation to the size of algal cells was found to be most important. Clay particle size should be similar to the algal cell size to obtain the best removal efficiency. Although some removal is expected in sea water, no effect is expected in lake water because of the effects of ionic strength.     

Protecting groups for glucuronic acid: application to the synthesis of new paclitaxel (taxol) derivatives

To prepare two new glucuronide conjugates, allyl ester and allyl carbonates were used as protecting groups of the glucuronic moiety. In this way, an aniline glycosyl carbamate spacer linked to the 2'-OH of paclitaxel was obtained. By using palladium chemistry, an efficient one-step removal of all the allyl groups at the end of the synthesis afforded the desired compounds in good yields.     

Enzymatic assay of marine bacterial phosphatases by capillary electrophoresis with laser-induced fluorescence detection

Microbial ectoenzyme activities in aquatic environments are important determinants of polymer hydrolysis and indicators of the state of microbial carbon, nitrogen, and phosphorus nutrition. Marine ectoenzymes are found on the cell surface or in the periplasmic space of gram-negative heterotrophic bacteria. Phosphatases, which remove phosphate groups from substrates, are one example of an ectoenzyme. Enzyme assays based on-capillary electrophoresis (CE) take advantage of CE's high-efficiency separation, extremely low sample volume requirements, and its ability to electrophoretically mix and separate zones of enzymes, substrates, and products all in one experimental run. CE has better resolving power and, when utilized with laser-induced fluorescence (LIF) detection, it is more sensitive than chromatography. CE-LIF is a promising tool for determining different phosphatases within a single microbial strain as well as the functional diversity between strains. In this study, four bacterial strains were studied (Shewanella sp., TW7, BB2AT2, and Vibrio alginolyticus) with each yielding at least one phosphatase that was kinetically characterized. K(m) values were calculated and found to be in the range of 0.0725-3.35 microM, whereas V(max) values ranged from 1.02 x 10(-3) to 1.05 x 10(-2) microM/min. The large range of values demonstrates differences among the phosphatases, suggesting different roles for each phosphatase not only between the species but also within a single bacterial species. This can have the important implications for organic matter processing in the sea.     

Reinforcing aluminium with cerium oxide: A new and effective technique to prevent corrosion in marine environments

Cerium oxide (CeO₂) is one of the potential choices to be explored for the protection of aluminium from corrosion. However, usage of cerium ions for surface modification of aluminium would not yield any potential effect in aggressive marine environments. Metal matrix composites of aluminium can have all the merits of aluminium such as density, strength, ductility and cost. In the present study, corrosion of aluminium in saline environment was significantly suppressed by means of reinforcing the aluminium with cerium oxide. The presence of cerium oxide in the matrix did not facilitate the formation of Al₂O₃ which would cause potential reshift after few days due to the onset of pitting. The present results strongly lay emphasis on the potential scope of use of CeO₂ for protection of aluminium in marine environments.