Search results for "Complex."
showing 10 items of 5824 documents
Design, synthesis and biological evaluation of new anticancer drugs: FGFR inhibitors
2021
Fibroblast growth factor receptors (FGFRs) constitute a family of tyrosine kinases receptors (RTKs) that exert pivotal physiological functions in human embryonic and adult tissues. Hyperactivated FGFR signaling drives tumorigenesis in multiple cancer types, including lung and brain cancers. Great effort has been laid on the development of new compounds that specifically target the FGFR axis. However, cancer cell- based and microenvironmental resistance mechanisms against FGFR inhibitors often arise and are currently poorly understood. Furthermore, FGFR-targeted therapy often presents different side effects, e due to the broad biological spectrum of the FGFR signaling axis as well as to its …
Tectonometamorphic evolution of high-pressure rocks from the island of Amorgos (Central Aegean, Greece)
2007
Structural and metamorphic data from the island of Amorgos (central Aegean Sea) show evidence for the existence of two distinct high-pressure units, the Metabasite Unit and the Basal Conglomerate Unit. These are exposed at the base of a thick marble sequence and overlying flysch deposits. The Metabasite Unit is characterized by a mineral assemblage of blue amphibole, garnet and clinopyroxene, indicating P – T conditions of 500–600 °C and >13 kbar. It is juxtaposed below carpholite-bearing metaconglomerates and quartz-rich micaschists of the Basal Conglomerate Unit, for which metamorphic conditions of 300–450 °C and 10–14 kbar are estimated. The contact between the two units is interpreted a…
Green determination of eight water-soluble B vitamins in cosmetic products by liquid chromatography with ultraviolet detection.
2021
Abstract B vitamins are a group of compounds with beneficious properties for dermatologic care, and therefore they are included in the cosmetic formulations as high added-value ingredients. In this paper, an analytical method for the simultaneous determination of eight water-soluble B vitamins in cosmetic products is reported for the first time. This method is based on liquid chromatography with ultraviolet detection (LC-UV) analysis after simple water leaching of the analytes from the cosmetic matrix. No organic solvents are required, beyond the ethanol used in the chromatographic mobile phase. The proposed method has been successfully validated showing good linearity, limits of detection …
Flow spectrophotometric determination of ammonium ion
1999
Abstract A flow procedure is proposed for the determination of ammonium ion. The sample in basic medium is forced through a solid-phase reactor containing immobilized AgCl on polymeric pearl beads. The released Ag + , complexed with the ammonia, gives a blue ternary complex with the aid of bromopyrogallol red and 1,10-phenanthroline which is spectrophotometrically monitored at 636 nm. The calibration graph is linear over the range 1–20 μg ml −1 ammonium ion, detection limit ( s / n = 3) 0.35 μg ml −1 and relative standard deviation (slope) 1.9 % ( n = 7). The sample throughput is 48 h −1 . The influence of foreign compounds is studied and the procedure is applied to ammonium ion determi…
Preliminary Results on the Use of Leather Chrome Shavings for Air Passive Sampling
2012
A new passive sampler based on low-density polyethylene (LDPE) layflat tube filled with chrome shavings from tannery waste residues was evaluated to determine volatile organic compounds (VOCs) in indoor and outdoor areas. VOCs were directly determined by head space-gas chromatography-mass spectrometry (HS-GC-MS) without any pretreatment of the sampler and avoiding the use of solvents. Limit of detection values ranging from 20 to 75 ng sampler−1and good repeatability values were obtained for VOCs under study with relative standard deviation values from 2.8 to 9.6% except for carbon disulfide for which it was 22.5%. The effect of the amount of chrome shavings per sampler was studied and resul…
The natural compound chrysosplenol-D is a novel, ultrasensitive optical sensor for detection of Cu(II)
2020
Abstract Herein, we introduce a novel, ultrasensitive optical sensor for determination of Cu(II) ions over the concentration range of 0 to 1 μM Cu(II). The optical sensor is based on the natural molecule chrysosplenol-D (Chp-D) extracted from the flowering plant Chiliadenus montanus (Vahl.) Brullo. Free Chp-D emits fluorescence at 566 nm when excited at 292 nm. Chp-D chelates Cu(II) ions to form a 1:1 (metal:ligand) complex, which quenches the fluorescence emission peak of the free probe at 566 nm. “Turn-off” luminescence could be easily determined and provided distinct proof of the chelation of Cu(II) ions by Chp-D. This novel optical sensor offers a considerable fluorescence mechanism (ch…
Screening and authentication of tea varieties based on microextraction-assisted voltammetry of microparticles
2015
Abstract A simple electrochemical methodology for screening and authentication of green, black and red tea varieties is proposed. It is based on the record of the voltammetric response of microparticulate films of antioxidant compounds resulting from an ethanolic micro-extraction of commercial tea herbal preparations in contact with aqueous buffers. The obtained voltammetric responses led us to differentiate between diverse tea varieties upon application of bivariant and multivariant chemometric techniques, including discrimination of mixtures of teas with sensitivity estimated of 5.0 μA mg −1 with a detection limit of 0.01 mg of tea sample. Under the proposed conditions 100% discrimination…
DETECTION LIMITS FOR NATURAL CIRCULAR-DICHROISM OF CHIRAL COMPLEXES IN THE X-RAY RANGE
1993
Whereas both Magnetic Circular Dichroism and Faraday Rotation studies have been successfully carried out at the K-, L- and M-absorption edges of metal atoms in ferromagnetic systems, Natural optical activity of chiral complexes has not yet been detected quite unambiguously in the X-ray range. We review a number of theoretical arguments which confirm that the optical asymmetry factor gσ should be very small in the X-ray range for unoriented powdered samples, especially at the K-absorption edges. This stimulating challenge prompted us to start an intensive programme of measurements aimed at detecting natural circular dichroism in both the soft and “firm” X-ray ranges. Although some of our ex…
eta1-Allypalladium complexes with tridentate PNP’ ligand for the assembly of modified Screen Printed Electrodes: an electrochemical study.
2015
Specific Pd-based organometallic complex, in particular the [Pd(η1-CH2–CH=CH2)(P–N–P’)]BF4 was used for the assembly of chemically modified Screen Printed Electrodes (SPEs) and their electrochemical reactivity was also investigated. For this purpose potassium ferricyanide, hexaammineruthenium(III) chloride, sodium hexachloroiridate-(III) hydrate, ascorbic acid (AA), uric acid (UA), acetaminophen (Ac), guanine (G) and adenine (A) were used to study the electron-transfer processes, which occurred at modified SPEs, fabricated by using the [Pd(η1-CH2–CH=CH2)(P–N–P’)]BF4, applying the drop casting procedure. Interesting results were obtained in the case of the guanine (G) quantitative detection,…
Determination of benzoylurea insecticides in food by pressurized liquid extraction and LC-MS
2010
A method based on pressurized liquid extraction and LC-MS/MS has been developed for determining nine benzoylureas (BUs) in fruit, vegetable, cereals, and animal products. Samples (5 g) were homogenized with diatomaceous earth and extracted in a 22 mL cell with 22 mL of ethyl acetate at 80 degrees C and 1500 psi. After solvent concentration and exchange to methanol, BUs were analyzed by LC-MS/MS using an IT mass analyzer, which achieved several transitions of precursor ions that increase selectivity providing identification. LOQs were between 0.002 and 0.01 mg/kg, which are equal or lower than maximum residue limits established by the Codex Alimentarius. Excellent linearity was achieved over…