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Monocarboxylate transporter 8 (MCT8) is a trans-membrane transporter, which mediates the cellular delivery of thyroid hormones, L-thyroxine (T4) and 3,5,3'-triiodo-L-thyronine (T3). In humans, the MCT8 protein is encoded by the SLC16A2 gene and mutations in the transporter cause a genetic neurological disorder known as Allan-Herndon-Dudley Syndrome (AHDS). MCT8 deficiency leads to impaired transport of thyroid hormones in the brain. Radiolabelled T4 and T3 or LC/MS-MS methods have been used to monitor the thyroid hormone uptake through MCT8. Herein, we developed a fluorescent based assay to monitor the thyroid hormone uptake through MCT8. A dansyl-based fluorescent probe having L-thyroxine moiety is found to be highly selective towards MCT8 in living cells. The high selectivity of the probe towards MCT8 can be attributed to the halogen bond-mediated recognition by the transporter protein. The presence of a free carboxylic acid group is essential for the specificity of the probe towards MCT8. Additionally, the selectivity of the probe for MCT8 is abolished upon esterification of the carboxylic group. Similarly, MCT8 does not recognize the probe when it contains a free amine group., (© 2024 Wiley-VCH GmbH.)

A polarity-sensitive probe was developed to simultaneously label lysosomes and endoplasmic reticulum (ER) via its dansylamide and rhodamine fluorescence, respectively, enabling ratiometric polarity detection and stable dual-labeling. The fragmented ER network and increased lysosomal polarity during ferroptosis were revealed, which facilitates the understanding of ferroptotic mechanisms.

Developing multifunctional nanomaterials with distinct photochemical properties, such as high quantum yield, improved photostability, and good biocompatibility is critical for a wide range of biomedical applications. Motivated by this, we designed and synthesized a dansyl-tagged xanthate-based capping agent (DX) for the synthesis of fluorescent silver nanoparticles (AgNPs). The capping agent DX was characterized by 1 H and 13 C-NMR, LC-MS, and FT-IR. The synthesized DX-capped fluorescent AgNPs were thoroughly characterized by UV-visible spectroscopy, fluorescence spectroscopy, field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), dynamic light scattering (DLS), and zeta potential. The fluorescent AgNPs showed distinct surface plasmon resonance absorption at λ max  = 414 nm, fluorescence at λ max  = 498 nm, quantum yield = 0.24, zeta potential = +18.6 mV, average size = 18.2 nm. Furthermore, the biological activity of the fluorescent AgNPs was validated by its interaction with the most abundant protein in the blood, that is, BSA (Bovine serum albumin) and HSA (Human serum albumin) with binding constant of 2.34 × 10 4  M -1 and 2.14 × 10 4  M -1 respectively. Interestingly, fluorescence resonance energy transfer (FRET) was observed between the fluorescent AgNPs and BSA/HSA with a FRET efficiency of 77.23% and 56.36%, respectively, indicating strong interaction between fluorescent AgNPs and BSA/HSA., (© 2024 American Society for Photobiology.)

Xylazine represents an increased threat to the recreational drug market. In this study, we present a rapid strategy for identifying xylazine and differentiating its common isomeric metabolites using Structures for Lossless Ion Manipulations (SLIM) ion mobility coupled to high-resolution/tandem mass spectrometry (IM-HRMS/MS). Chemical derivatization using dansyl chloride also assisted with separations and led to identification of resolvable reaction product atropisomers.

In this paper, the development and application of a multiple heart-cutting achiral-chiral LC-LC method (mLC-LC) for the analysis of dansylated (Dns) branched-chain amino acids in commercial tablets are described. In the first dimension, a Waters Xbridge RP C18 achiral column was used under gradient conditions with buffered aqueous solution and acetonitrile. The elution order Dns-valine (Dns-Val) < Dns-isoleucine (Dns-Ile) < Dns-leucine (Dns-Leu) turned out with full resolution between adjacent peaks: 7.25 and 1.50 for the Val/Ile and the Ile/Leu pairs, respectively. A "research" validation study was performed, revealing high accuracy (Recovery%) and precision (RSD%) using two external set solutions, respectively, in the range 93.7%-104.1% and 0.4%-3.2%. The C18 column was connected via a two-position six-port switching valve to the quinidine-based Chiralpak quinidine-anion-exchange chiral column. A water/acetonitrile, 30/70 (v/v) with 50 mM ammonium acetate (apparent pH of 5.5) eluent allowed getting the three enantiomers' pairs resolved: R S equal to 4.3 for Dns-Val and Dns-Ile, and 1.7 for Dns-Leu. The application of the mLC-LC method confirmed that the content of Val, Ile, and Leu in the tablets was compliant with that labeled by the producer. Only l-enantiomers were found in the food supplement, as confirmed by LC-MS/MS analysis., (© 2024 Wiley‐VCH GmbH.)

The accurate detection of biogenic amines (BAs) is an important means of ensuring the quality and safety of cephalopod seafood products. In this study, the pre-column derivatization of high-performance liquid chromatography (HPLC) was optimized using dansyl chloride (Dns-Cl) to detect BAs in octopus, cuttlefish, and squid. The reasons for the formation of BAs were investigated by assessing their decarboxylase activity and the rates of decomposition. The findings demonstrated that using Dns-Cl to optimize pre-column derivatization enabled the separation of nine different BAs. The detection limits ranged from 0.07 to 0.25 mg/L, and the results exhibited a high level of linearity (R 2  ≥ 0.997). The decarboxylase activity and biodegradation rate positively correlated with the formation of BAs at temperatures below 0°C. Notably, the decarboxylase activity of octopus, cuttlefish, and squid exhibited a significant increase with prolonged storage time, and formyltransferase and carbamate kinase may be the key decarboxylase in cephalopod products. These findings serve as a valuable reference for further investigations into the mechanisms behind BAs production and the development of control technologies for BAs in cephalopod products. This study has successfully demonstrated the effectiveness of the Dns-Cl pre-column derivatization-HPLC method in accurately and efficiently detecting BAs in octopus, cuttlefish, and squid. Moreover, it highlights the influence of decarboxylase content and biodegradation rate on the formation of BAs. Importantly, this method can serve as a reference for detecting BAs in various seafood products., (© 2024 Institute of Food Technologists.)

Glycosaminoglycans (GAGs), such as heparan sulfate (HS), play essential roles in living organisms. Understanding the functionality of HS and its involvement in disease progression necessitates the sensitive and quantitative detection of HS-derived unsaturated disaccharides. Conventionally, fluorescence derivatization precedes the HPLC analysis of these disaccharides. However, the presence of excess unreacted derivatization reagents can inhibit rapid and sensitive analysis in chromatographic determinations. In this study, we describe analytical methods that use dansylhydrazine as a derivatization agent for the detection and determination of HS-derived unsaturated disaccharides using HPLC. In addition, we have developed a straightforward method for removing excess unreacted reagent using a MonoSpin NH 2 column. This method may be employed to remove excess pre-labeling reagents, thereby facilitating the analysis of HS-derived unsaturated disaccharides with satisfactory reproducibility.

Liquid chromatography mass spectrometry (LC-MS) has been increasingly used for metabolome analysis. One of the critical steps in the LC-MS metabolome analysis workflow is related to metabolite identification. Among the measured parameters, peak mass is commonly used to search against a database for potential metabolite matches. Higher accuracy mass measurement allows the use of a narrower mass tolerance window for mass search. While various types of mass analyzers can routinely measure a peak mass with an error of less than a few ppm, mass measurement accuracy is not uniform for peaks with different intensities, particularly for quadrupole time-of-flight (QTOF) MS. Herein we present a simple and convenient method to determine the relation between peak intensity and mass error in LC-QTOF-MS-based metabolome analysis, followed by intensity-dependent mass search (IDMS) of a database for metabolite matches. This method is based on running a series of sodium formate mass calibrants, as part of the standard operating procedure (SOP) in LC-MS data acquisition, and then curve-fitting the measured mass errors and peak intensities. We show that, in two different quadrupole time-of-flight (QTOF) mass analyzers, mass accuracy is generally reduced as peak intensity decreases, which is independent of m/z values in the range commonly used for metabolite detection (e.g., m/z < 1000). We demonstrate the improvement in metabolite matches using IDMS in the analyses of dansyl labeled standards and human urine samples. We have implemented the IDMS method in the freely available MCID database at www.mycompoundid.org, which is composed of 8021 known human endogenous metabolites and their predicted metabolic products (375,809 compounds from one metabolic reaction and 10,583,901 compounds from two reactions)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Background & Aims: Transport functions of albumin are of clinical and pharmacological interest and are determined by albumin's properties like posttranslational modifications or bound ligands. Both are affected in pathological conditions and in therapeutic grade albumin solutions. The term effective albumin concentration was introduced as a measure of functionally intact albumin. Our aim was to evaluate the impact of ligands and modifications with different approaches as a measure of effective albumin., Approach & Results: We used a spin labelled fatty acid and dansylsarcosine to characterize binding properties of albumin i) prepared from plasma of patients and healthy control donors, ii) measured directly out of plasma, iii) research grade albumin, iv) in vitro modified albumin, and v) therapeutic infusion solutions before and after removal of stabilizers. Bilirubin is the main determinant for binding function in patients' albumin. In in vitro prepared albumin bound fatty acids correlated with impaired binding. Human nonmercaptalbumin1, not human nonmercaptalbumin2, showed reduced binding properties. Binding and transport function of therapeutic albumin was severely impaired and restored by filtration. Glycation of research grade albumin had no effect on the binding of dansylsarcosine and only a minor effect on fatty acid binding., Conclusions: Our results suggest that effective albumin -in terms of binding properties- is primarily determined by bound ligands and only to a minor extent by posttranslational modifications. Characterizing albumin directly from plasma better reflects the physiological situation whereas in the case of therapeutic grade albumin stabilizers should be removed to make its binding properties accessible., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Karl Oettl is a consultant of Takeda Pharmaceuticals International AG., (Copyright © 2023. Published by Elsevier B.V.)

Herein, a standalone software equipped with a graphic user interface (GUI) is developed to predict liquid chromatography mass spectrometry (LC-MS) retention times (RTs) of dansylated metabolites. Dansylation metabolomics strategy developed by Li et al. narrows down a vast chemical space of metabolites into the metabolites containing amines and phenolic hydroxyls. Combined with differential isotope labeling, e.g., 12 C-reagent labeled individual samples spiked with a 13 C-reagent labeled reference or pooled sample, LC-MS analysis of the dansylated samples enables accurate relative quantification of all labeled metabolites. Herein, the LC-RTs for dansylated metabolites are predicted using an artificial neural network (ANN) machine-learning model. For the ANN modeling, 315 dansylated urine metabolites obtained from the DnsID database are used. The ANN LC-RT prediction model was reliable, with a mean absolute deviation of 0.74 min for the 30 min LC run. In the RT model, a deviation of more than 2 min was observed in only 3.2% of the total 315 metabolites, while a deviation of 1.5 min or more was observed in 11% of the metabolites. Furthermore, it was found that the LC-RT prediction was also reliable even for metabolites containing both amine and phenolic functional groups that can undergo dansylation on either one of the two functional groups, resulting in the generation of two isomeric forms. This RT-prediction model is embedded into a user-friendly GUI and can be used for identifying nontargeted dansylated metabolites with unknown RTs, along with accurate mass measurements. Furthermore, it is demonstrated that the developed software can help identify metabolites from a urine sample of an anonymous healthy pregnant woman., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest. The funder had no role in the design of the study; in the collection, analyzes, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Dipeptides have recently attracted considerable attention due to their newly found biological functions and potential biomarkers of diseases. Global analysis of dipeptides (400 common dipeptides in total number) in samples of complex matrices would enable functional studies of dipeptides and biomarker discovery. In this work, we report a method for high-coverage detection and accurate relative quantification of dipeptides. This method is based on differential chemical isotope labeling (CIL) of dipeptides with dansylation and liquid chromatography Orbitrap tandem mass spectrometry (LC-Orbitrap-MS). An optimized LC gradient ensured the separation of dansyl-dipeptides, including positional isomers (e.g., leucine- and isoleucine-containing dipeptides). MS/MS collision energy in Orbitrap MS was optimized to provide characteristic fragment ion information to sequence dansyl-dipeptides. Using the optimized conditions, a CIL standard library consisting of retention time, MS, and MS/MS information of a whole set of 400 dansyl-dipeptides was constructed to facilitate rapid dipeptide identification. For qualitative analysis of dipeptides in real samples, IsoMS data processing software's parameters were tuned to improve the coverage of dipeptide annotation. Data-dependent acquisition was also carried out to improve the reliability of dipeptide identification. As examples of applications, we successfully identified a total of 321 dipeptides in rice wines and 105 dipeptides in human serum samples. For quantitative analysis, we demonstrated that the intensity ratios of the peak pairs from 96% of the dansyl-dipeptides detectable in a 1:1 mixture of 12 C- and 13 C-labeled rice wine samples were within ±20% of an expected value of 1.0. More than 90% of dipeptides were detected with a relative standard deviation of less than 10%, showing good performance of relative quantification.

Although chemoselective labeling strategies show great potential in in-depth description of metabolomics, the associated time and expense limit applications in high-throughput and routine analysis. We report a fast and effective chemoselective labeling strategy based on multifunctionalized monolithic probes. A rapid pH-responsive boronate ester reaction was employed to immobilize and release probe molecules from substrate in 5 min. The mesoporous surface and hierarchically porous channels of the substrate allowed for accelerated labeling reactions. Moreover, the discernible boron beacons allowed for recognition of labeled metabolites with no need for expensive isotopic encoding. This new strategy has been successfully used for submetabolome analysis of yeast cells, serum, and faeces samples, with improved sensitivity for short chain fatty acids up to 1 600 times compared with non-labeled liquid chromatography-mass spectrometry (LC-MS) methods., (© 2022 Wiley-VCH GmbH.)

Chemical isotope labeling (CIL) LC-MS is a powerful tool for metabolome analysis with markedly improved metabolomic coverage and quantification accuracy over the conventional LC-MS technique. In addition, with differential isotope labeling, each labeled metabolite is detected as a peak pair in the mass spectra, offering the possibility of differentiating true metabolite peaks from the singlet noise or background peaks. In this study, we examined the effects of instrument type on the detectability of true metabolites with a focus on the comparison of quadrupole time-of-flight (QTOF) and Orbitrap mass spectrometers. Using the same ultra-high-performance liquid chromatography setup and optimized running conditions for QTOF and Orbitrap, we compared the total number of peak pairs detected and identified from the two instruments using human urine and serum as the test samples. Many common peak pairs were detected from the two instruments; however, there were a significant number of unique peak pairs detected in each type of instrument. By combining the datasets obtained using QTOF and Orbitrap, the total number of peak pairs detected could be significantly increased. We also examined the effect of mass resolving power on peak pair detection in Orbitrap (60,000 vs. 120,000 resolution). The observed differences in peak pair detectability were much less than those of QTOF vs. Orbitrap. However, the type of peak pairs detected using different resolutions could be somewhat different, offering the possibility of increasing the overall number of peak pairs by combining the two datasets obtained at two different resolutions. The results from this study clearly indicate that instrument type can have a profound effect on metabolite detection in CIL LC-MS. Therefore, comparison of metabolome data generated using different instruments needs to be carefully done. Moreover, future research (e.g., hardware modifications) is warranted to minimize the differences in order to generate more reproducible metabolome data from different types of instruments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

We report a segmented spectrum scan method using Orbitrap MS in chemical isotope labeling (CIL) liquid chromatography-mass spectrometry (LC-MS) for improving the metabolite detection efficiency. In this method, the full m / z range is divided into multiple segments with the scanning of each segment to produce multiple narrow-range spectra during the LC data acquisition. These segmented spectra are separately processed to extract the peak pair information with each peak pair arising from a differentially labeled metabolite in the analysis of a mixture of 13 C and 12 C reagent-labeled samples. The sublists of peak pairs are merged to form the final peak pair list from the LC-MS run. Various experimental conditions, including automatic gain control (AGC) values, mass resolutions, segment m / z widths, number of segments, and total data acquisition time in the LC run, were examined to arrive at an optimal setting in the segment scan for increasing the number of detectable metabolites while maintaining the same analysis time as in the full scan. The optimal method used a segment width of 120 m / z with 60k resolution for a 16 min CIL LC-MS run. Using dansyl-labeled human urine samples as an example, we demonstrated that this method could detect 5867 peak pairs or metabolites (not features), compared to 3765 peak pairs detectable in a full scan, representing a 56% gain. Out of 5867 peak pairs, 5575 (95.0%) could be identified or mass-matched. The relative quantification accuracy was slightly reduced (81% peak pairs were within ±25% of the expected peak ratio of 1.0 in full, compared to 87% in the full scan) due to the inclusion of more low-abundance peak pairs in the segment scan. The peak ratio measurement precision was not significantly affected by the segment scan. We also showed the increase of the peak pair number detectable from 3843 in the full scan to 7273 (89% gain) using the Orbitrap operated at 120k resolution with a 60 m / z segment width when multiple repeat sample injections were used. Thus, segment scan Orbitrap MS is an enabling method for detecting coeluting metabolites in CIL LC-MS for increasing the metabolomic coverage.

A new and innovative fluorescent structure was constructed on Cyclotriveratrylene affiliated to Dansyl chloride (DNSC) and was used to detect Cr (III) and Fe (III) among the various cations by using spectrofluorimetric method. The characterization of the new compound was carried out using the 1 H-NMR, 13 C-NMR, and ESI-MS techniques. The interaction and role of DNSC-CTV with cations was reviewed. A change in the spectra of absorption directed to the conclusion that there is substantial interaction of Cr (III) and Fe (III) with DNSC-CTV. Furthermore the interaction of the ligand DNSC-CTV with the metal ions Chromium (III) and Iron (III) showed quenching in the emission spectra. Quantum yield of the complexes were calculated and the stern volmer analysis was done to deduce the quenching mechanism of fluorescence to being either static or dynamic. The molecule DNSC-CTV was further studied with the help of computational methods such as molecular docking to study the binding interactions and properties of the molecule., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

A simple pH fluorescent probe based on dansyl derivative (Bu-Dns) was synthesized via one-step reaction between dansyl chloride and 4-bromobutan-1-amine hydrobromide. The obtained probe showed good selectivity and sensitivity toward H + in acidic medium over two pH units (~4-2). At pH > 4, Bu-Dns solution emitted yellow fluorescent light, which became gradually weaker with decreasing pH value. At pH below 2, complete fluorescence quenching occurred. The pH response of Bu-Dns was ascribed to the protonation of dimethylamine group. The lack of influence of metal ion on pH response increases the prevalence of Bu-Dns in the potential detection of pH variation in acidic aqueous media. More importantly, it can sense the intracellular pH change in acidic range., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Sphingosine-1-phosphate (S1P) synthesized by sphingosine kinase (SPHK) is a signaling molecule, involved in cell proliferation, growth, differentiation, and survival. Indeed, a sharp increase of S1P is linked to a pathological outcome with inflammation, cancer metastasis, or angiogenesis, etc. In this regard, SPHK/S1P axis regulation has been a specific issue in the anticancer strategy to turn accumulated sphingosine (SPN) into cytotoxic ceramides (Cers). For these purposes, there have been numerous chemicals synthesized for SPHK inhibition. In this study, we investigated the comparative efficiency of dansylated PF-543 (DPF-543) on the Cers synthesis along with PF-543. DPF-543 deserved attention in strong cytotoxicity, due to the cytotoxic Cers accumulation by ceramide synthase (CerSs). DPF-543 exhibited dual actions on Cers synthesis by enhancing serine palmitoyltransferase (SPT) activity, and by inhibiting SPHKs, which eventually induced an unusual environment with a high amount of 3-ketosphinganine and sphinganine (SPA). SPA in turn was consumed to synthesize Cers via de novo pathway. Interestingly, PF-543 increased only the SPN level, but not for SPA. In addition, DPF-543 mildly activates acid sphingomyelinase (aSMase), which contributes a partial increase in Cers. Collectively, a dansyl-modified DPF-543 relatively enhanced Cers accumulation via de novo pathway which was not observed in PF-543. Our results demonstrated that the structural modification on SPHK inhibitors is still an attractive anticancer strategy by regulating sphingolipid metabolism.

Catecholamines and steroids are well-known neurotransmitters and hormones that rapidly change the excitability of neurons. Alopecia areata is a disease for which the exact cause is unknown, but it is considered to be associated with stress, and so the simultaneous analysis of catecholamines and steroids is required for the diagnosis of alopecia areata. Thus, we herein report the simultaneous analysis of catecholamines and steroids bearing different functional groups for the first time, during which it was necessary to carry out a serial hydrolysis procedure. Following hydrolysis of the urine samples to produce the free forms from the urinary conjugates, ethyl acetate extractions were carried out, and chemical derivatization was performed using dansyl chloride to increase the sensitivity of the liquid chromatography-tandem mass spectrometry method. The matrix effects and recoveries of this analytical method were validated, giving values of 85.4-122.9% and 88.8-123.0%, respectively. In addition, the method accuracy and precision were assessed, giving values of 0.4-21.5% and 2.0-21.6% for the intra-day and inter-day precisions, respectively. This validated method was then applied to identify differences between patients with and without alopecia areata, wherein the metanephrine content was found to be significantly higher in the alopecia areata patient group. This quantitative profiling method can also be applied to steroid-dependent diseases, as well as catecholamine-related diseases.

Herein, the fabrication of a fascinating multifunctional cyclodextrin (CD) chiral stationary phase and its chiral separation performance in capillary electrochromatography are proposed. A facile interfacial polymerization was used to anchor ethanediamine-β-cyclodextrin (EDA-β-CD) polymerized with trimesoyl chloride (TMC) and to form the chiral stationary phase (CSP) composite onto the surface wall of the capillary. The characters of prepared columns were confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray Photoelectron Spectrometer (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). This novel CSP offers multi-typical interactions including hydrogen bonding, π-interaction, hydrophobic and electrostatic interaction as well as steric effects which contribute to prominent chiral recognition for Dansyl-DL-amino acids in CEC modes. The EDA-β-CD modified column showed eminent enantioseparation performance towards five Dansyl-DL-amino acids (the DL-forms of valine, threonine, leucine, phenylalanine, serine). Besides, the prepared columns were perfectly reproducible and stable. The relative standard deviations of the enantiomer retention times for intra-day (n = 5), inter-day (n = 3) runs and column-to-columns (n = 3) are below 0.54%, 1.35% and 4.89%, individually. This innovative chiral stationary phase shows a broader application view and scope in chiral recognition domain., Competing Interests: Declaration of Competing Interest Authors declare no conflict of interest., (Copyright © 2021. Published by Elsevier B.V.)

Here we present a novel peptide-based fluorescent "turn-on" molecule P1 for detecting RNA, in a double or single strand, AU-rich or CG-rich. Both computational and experimental studies indicate that the detection efficiency depends on the binding affinity of P1 and conformational changes. P1 could be applied for cell imaging without any additional transfection vectors. Selective detection of RNA in cells was determined by RNase digestion. Successful application of P1 for RNA imaging in cell mitosis reveals that it may have broad applications in research, biotechnology and medical science.

The aim of this work was to characterize biogenic amines (BAs) in different parts of Lycium barbarum L. using HPLC with dansyl chloride derivatization, and jointly, to provide referential data for further exploration and utilization of Lycium barbarum L. The linear correlation coefficients for all BAs were above 0.9989. The limits of detection and quantification were 0.015-0.075 and 0.05-0.25 μg/mL, respectively. The relative standard deviations for the intra-day and inter-day precision were 0.66-2.69% and 0.91-4.38%. The described method has good repeatability and intermediate precision for the quantitative determination of BAs in different parts of Lycium barbarum L. Satisfactory recovery for all amines was obtained (79.3-110.3%). The result showed that there were four kinds of BAs. The highest putrescine content (20.9 ± 3.2 mg/kg) was found in the flower. The highest histamine content (102.7 ± 5.8 mg/kg) was detected in the bark, and the highest spermidine (13.3 ± 1.6 mg/kg) and spermine (23.7 ± 2.0 mg/kg) contents were detected in the young leaves. The high histamine (HIS) content in the bark may be one of the reasons why all of the parts of Lycium barbarum L., except the bark, are used for medicine or food in China. Meanwhile, the issue of the high concentration of HIS should be considered when exploiting or utilizing the bark of Lycium barbarum L.

A sensitive liquid chromatography-tandem mass spectrometry (LC-MS) method was developed for the screening of five β-blockers (BBs), including atenolol, metoprolol, bisoprolol, propranolol, and betaxolol, in rabbit plasma. An inhouse prepared hydrazonoyl chloride compound (UOSA54) and dansyl chloride (DNS) were successfully coupled with BBs via the amino functional group and analyzed by LC-MS/MS. The excess hydrazonoyl chloride was characterized by a negligible ionization suppression at the electrospray-ionization (ESI) source, which enables the analysis of BBs at a low concentration level. The relative ESI-MS response of derivatized to underivatized BBs was enhanced 2.3 to 3.7-fold. The developed method could be applied for screening of BBs in samples by searching the most abundant MS product ions, including m/z 169 and 211, in addition to the precursor ion and the cleavage of ether moiety. The method could be applied for trace analysis and screening of BBs abuse. The use of UOSA54 was adventitious over dansylated derivatives because of minimal reaction by-products and the negligible ionization suppression effect. The extraction efficiency of BBs from rabbit plasma was improved to reach 77.5-93.9% using tert-butylamine and Chromabond® C18ec-100 mg column. The optimal reaction conditions were optimized and validated. The linear range of analyzed BBs in rabbit plasma was within the range of 0.1 to 25.0 ng/mL, while the limit of quantification (LO Q) was ranged from 0.10 to 0.25 ng/mL., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A reversible fluorescent probe DRhFe is devised by linking spirolactam rhodamine and dansylamide through an Fe 3+ ionophore N 2 -hydroxyethyldiethylenetriamine, where Fe 3+ chelation generating rhodamine B can switch intramolecular fluorescence resonance energy transfer for ratiometric Fe 3+ sensing. Probe DRhFe exhibits an Fe 3+ -specific emission shift from 483 to 576 nm, and this ratiometric response has been successfully applied to monitor labile Fe 3+ fluctuations in cells undergoing ferroptosis.

Labile ferrous iron (Fe 2+ ) plays important biochemical functions in many physiologically essential processes. It is very important to find an effective method to detect Fe 2+ . Herein, a simple and effective Fe 2+ fluorescent probe (FeP1) has been constructed via a unique strategy of Fe 2+ -induced reducing reaction. As expected, FeP1 exhibited a 'turn-on' fluorescence response toward Fe 2+ over various small analytes, with high selectivity and excellent sensitivity (DL = 18 nM) for the detection of Fe 2+ in Tris-DMSO (4:1, pH = 7.4, v/v) solution. Moreover, the probe can act in different real samples, such as physiological saline and living cells., Competing Interests: Declaration of competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, “A simple and effective dansyl acid based “turn-on” fluorescent probe for detecting labile ferrous iron in physiological saline and live cells”., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Blood metabolomics has been widely used for discovering potential metabolite biomarkers of various diseases. In this study, we report our investigation of the effects of freeze-thaw cycles (FTCs) of human serum samples on quantitative metabolomics using a differential chemical isotope labeling (CIL) LC-MS method. A total of 99 serum samples collected from healthy individuals (47 females and 52 males) were subjected to five FTCs, followed by 12 C-/ 13 C-dansylation labeling LC-MS analysis. A total of 2790 peak pairs or metabolites were relatively quantified among the 495 comparative samples, including 150 positively identified metabolites, 235 high-confident putatively identified metabolites and 1949 mass-matched metabolites from database searches. Multivariate analysis of the metabolome data showed a clustering of the third to fifth FTC samples in contrast to the separation of the first and second FTC samples, indicating that the extent of FTC-induced metabolome changes became smaller after the third cycle. The changing patterns among the FTC-effected metabolites were found to be complex. Using sex as a biological factor for grouping, we observed a clear separation of males and females when the samples were subjected to the same number of FTCs. However, when the male- and female-samples with different numbers of FTCs were compared, the number of significant metabolites found in male-female comparison increased dramatically, indicating that FTC effects could lead to a large number of false positives in biomarker discovery. Finally, we proposed a method of detecting the FTC effects by reanalyzing the original samples after subjecting them to an additional FTC.

A new derivatization reagent, N-(naphthalen-1-yl)-2-oxopropanehydrazonoyl chloride (UOSA54), was prepared and coupled with four drugs, bearing primary amino, secondary amino or mercapto functional groups. Glucosamine sulfate (GLU), cysteine (CYS), captopril (CAP), and vildagliptin (VIL), were used as representative reactive analytes. The prepared reagent was successfully coupled with the targeted analytes in the presence of triethylamine (TEA) as hydrochloride acceptor and acetonitrile as solvent. The resulting reaction products were separated by high-performance liquid chromatography and monitored simultaneously by diode array and triple quad mass spectrometry detectors. Enhanced DAD and electrospray ionization-MS (ESI-MS) responses were observed for the derivatized products. Complete derivatization of VIL was achieved after heating at 65 ± 3 °C for 4 min, while other analytes were derivatized instantaneously at room temperature. Both, the ESI-ionization suppression, due to the excess reagent, and matrix effect, due to co-eluted biogenic plasma constituents, were negligible. The derivatized GLU, CYS, CAP, and VIL showed a maximum absorption wavelength at 376, 417, 340, and 376 nm, with MS-limit of quantification value of 250.0, 2.0, 2.5, and 3.0 pg/μL, respectively. The relative ESI-MS response of UOSA54 derivatization products was within the range of 0.6-4.1 compared with dansylated products. The method was optimized and validated for optimal reaction product stability, sensitivity, linearity, range, precision, and accuracy. The percentage recovery was exceeding 97.2%, with an RSD value of less than 4.0%. The limit of quantification of targeted analytes was ranged from 80.0 to 0.7 pg/μL., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Yeast-derived β-glucan particles (GPs) are a class of microcarriers under development for the delivery of drugs and imaging agents to immune-system cells for theranostic approaches. However, the encapsulation of hydrophilic imaging agents in the porous GPs is challenging. Here, we show that the unique coordination chemistry of Fe III -based macrocyclic T 1 MRI contrast agents permits facile encapsulation in GPs. Remarkably, GPs labeled with the simple Fe III complexes are stable under physiologically relevant conditions, despite the absence of amphiphilic groups. In contrast to the free Fe III coordination complex, the labeled Fe III -GPs have lowered T 1 relaxivity and act as a silenced form of the contrast agent. Addition of a fluorescent tag to the Fe III complex produces a bimodal agent to further enable tracking of the nanoparticles and to monitor release. Treatment of the iron-labeled GPs with a maltol chelator or with mildly acidic conditions releases the intact iron complex and restores enhanced T 1 relaxation of the water protons., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bacterial transglutaminase was used to label human plasma proteins with fluorescent tags. Protein lysines were modified with dansyl-epsilon-aminohexyl-Gln-Gln-Ile-Val-OH (dansylQQIV), while protein glutamines were modified with dansyl cadaverine. Labeled proteins included human butyrylcholinesterase, apolipoprotein A-1, haptoglobin, haptoglobin-related protein, immunoglobulin heavy chain, and hemopexin. Tryptic peptides were analyzed by LC-MS/MS on an Orbitrap Fusion Lumos mass spectrometer. Modified residues were identified in Protein Prospector and Proteome Discoverer searches of mass spectrometry data. The MS/MS fragmentation spectra from dansylQQIV-modified peptides gave intense peaks at 475.2015, 364.1691, 347.1426, 234.0585, and 170.0965 m / z . These signature ions are useful markers for identifying modified peptides. Human butyrylcholinesterase retained full activity following modification by dansylQQIV or dansyl cadaverine.

Ibotenic acid (IBA) is an amino acid and muscimol (MUS) is the decarboxyl derivative of IBA. They are mushroom neurotoxins with high polarity and low molecular weight. Only one transition (159->113 for IBA and 115->98 for MUS) can be found when directly measured by high performance liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). Therefore, the identification and quantification of trace amount of the toxins in biomaterial are difficult. A highly sensitive and accurate analytical method for IBA and MUS in plasma was developed by LC-MS/MS with the application of bimolecular dansylation and internal standard calibration. Acetonitrile was used for protein precipitation and for toxin extraction from plasma. The toxins and internal standards (L-tyrosine- 13 C 9 , 15 N for IBA and tyramine-d 4 for MUS) were derivatized with dansyl chloride (DNSCl). The reaction conditions of the bimolecular dansylation were optimized and the fragmentation pathways of the derivatives in MS/MS were studied. Method validation was carried out according to the Bioanalytical Method Validation Guidance for Industry (FDA, USA, 2018). The limits of detection for IBA and MUS in plasma were 0.3 ng mL -1 and 0.1 ng mL -1 , respectively. The linear ranges in plasma were 1-500 ng mL -1 and 1-200 ng mL -1 with the correlation coefficients of 0.998 and 0.999 for IBA and MUS, respectively. The recoveries at three spiked levels were 90.7-111.4% with relative standard deviations (RSDs) of 6.4-10.3% for IBA and the results were 85.1-94.2% with RSDs of 5.0-8.9% for MUS. The toxin levels in patients' plasma samples under different poisoning degree were presented., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Starting from dansyl-chloride, in reaction with 1,1-diphenylhydrazine and methoxyamine, two new fluorescent derivatives 1 and 2 were obtained and characterized by NMR, IR, UV-Vis, HR-MS, and fluorescence spectroscopy. The single-crystal X-ray structure was obtained for compound 2 . Both compounds generate free radicals by oxidation, as demonstrated by ESR spectroscopy. Compound 1 generates the corresponding hydrazyl-persistent free radical, evidenced directly by ESR spectroscopy, while compound 2 generates in the first instance the methoxyaminyl short-lived free radical, which decomposes rapidly with the formation of the methoxy radical, evidenced by the ESR spin-trapping technique. By oxidation of compounds 1 and 2 , their fluorescence is quenched.

Free fatty acid (FFA) and acylcarnitine (AcCar) are key elements of energy metabolism. Dysregulated levels of FFA and AcCar are associated with genetic defects and other metabolic disorders. Due to differences in the physicochemical properties of these two classes of compounds, it is challenging to quantify FFA and AcCar in human plasma using a single method. In this work, we developed a chemical isotope labeling (CIL)-based liquid chromatography-multiple reaction monitoring (LC-MRM) method to simultaneously quantify FFA and AcCar. Dansylhydrazine (DnsHz) was used to label the carboxylic acid moiety on FFA and AcCar. This resulted in the formation of a permanently charged ammonium ion for facile ionization in positive ionization mode and higher hydrophobicity for enhanced retention of short-chain analogs on reversed-phase LC columns and enabled absolute quantification by using heavy labeled DnsHz analogs as internal standards. Labeling conditions including the concentration and freshness of cross-linker, reaction time, and temperature were optimized. This method can successfully quantify all short-, medium- and long-chain FFAs and AcCars with greatly enhanced sensitivity. Using this method, 25 FFAs and 13 AcCars can be absolutely quantified and validated in human plasma samples within 12 min. Simultaneous quantification of FFA and AcCar enabled by this CIL-based LC-MRM method facilitates the investigation of fatty acid metabolism and has potential in clinical applications.

pH fluorescent probes possess many advantages, including intracellular detection, rapid response time and nondestructive testing. In this paper, a highly selective and sensitive fluorescent pH probe based on triethylenetetramine bearing double dansyl groups (1) was synthesized. This probe offers fluorescent measurement of pH value in the range of 5.81-7.21 in aqueous solution, with an 8.64-fold enhancement of fluorescent emission intensity over the unmodified probe. Probe 1 shows a fluorescent color change from a pale yellow to bright green when the pH is increased from 5.81 to 7.21. In addition, probe 1 shows good potential as a fluorescent visualizing sensor for pH values in living GS cells of epinepheluscoioides. The mechanism of the fluorescent response of probe 1 to solution pHs was further clarified by NMR, fluorescent spectra, and UV-vis absorption spectra. The results indicate that the fluorescent emission will shift with an increase in solution pHs, due to increasing deprotonation of the nitrogen atom on the sulfonamides. Deprotonation of the sulfonamide group will inhibits the intramolecular charge transfer process between the imino group and the naphthalene ring, resulting in the recognition phenomenon of blue shift and enhancement of fluorescent emission intensity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Steroid hormones are a type of crucial substances that mediate numerous vital physiological functions. The comprehensive detection of steroid hormones can help understand the physiopathologic mechanism of steroid hormone-related diseases. It is very difficult to determine steroid hormones in biological samples due to their low endogenous concentrations and poor ionization efficiency. In this study, an efficient and sensitive approach was developed for profiling steroid hormones by combining liquid-liquid extraction and parallel derivatization with liquid chromatography-tandem mass spectrometry. Methoxyamine and dansyl chloride were used to derivatize steroid hormones containing carbonyl and phenolic hydroxyl groups, respectively. Our established method achieved simultaneous analysis of carbonyl and phenolic hydroxyl-containing steroid hormones and could cover estrogens, androgens, corticoids and progestogens. Twenty-nine steroid hormones were detected at pg/mL levels with the sensitivity enhanced by three orders of magnitude after derivatization. The linearity (with linear range of 2-4 orders of magnitude), precision (less than 15%) and recovery (71.1-128.7%) were satisfactory for quantitative analysis of steroid hormones. Finally, the established method was successfully employed to the determination of steroid hormones in serum samples of healthy males and females as well as ovarian cancer patients. The results showed that this approach was suitable and reliable for routine test of steroid hormones containing carbonyl and phenolic hydroxyl groups., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019. Published by Elsevier B.V.)

Calix[4]pyrrole phosphonate-cavitands were used as receptors for the design of supramolecular sensors for creatinine and its lipophilic derivative hexylcreatinine. The sensing principle is based on indicator displacement assays of an inherently fluorescent guest dye or a black-hole quencher from the receptor's cavity by means of competition with the creatinine analytes. The systems were thermodynamically and kinetically characterized regarding their 1:1 binding properties by means of nuclear magnetic resonance spectroscopy ( 1 H and 31 P NMR), isothermal titration calorimetry, and optical spectroscopies (UV/vis absorption and fluorescence). For the use of the black-hole indicator dye, the calix[4]pyrrole was modified with a dansyl chromophore as a signaling unit that engages in Förster resonance energy transfer with the indicator dye. The 1:1 binding constants of the indicator dyes are in the range of 10 7 M -1 , while hexylcreatinine showed values around (2-4) × 10 5 M -1 . The competitive displacement of the indicators by hexylcreatinine produced supramolecular fluorescence turn-on sensors that work at micromolar analyte concentrations that are compatible with those observed for healthy as well as sick patients. The limit of detection for one of the systems reached submicromolar ranges (110 nM).

Mercury is one of the most hazardous pollutants, and mercury pollution is a serious hazard to our environment. Herein, we designed and synthesized a new peptide-based fluorescent chemosensor (L) based on a Fmoc-Lys (Fmoc)-OH backbone conjugated with two Serines and dansyl groups using solid phase peptide synthesis (SPPS) technology. L exhibited highly selective and excellent sensitive detection of Hg 2+ ions in 100% aqueous solutions through fluorescence quenching. The chemosensor L forms a 2:1 stoichiometry with high binding constants (4.89×10 6 M -1 ) and the detection limit for Hg 2+ ions of the proposed assay was 7.59nM. In addition, the recovery test results of Hg 2+ concentration in actual water samples showed that the quantitative detection of Hg 2+ ions can be realized in two water samples. Moreover, L showed low cytotoxicity and excellent membrane permeability in HK2 cells, which has been successfully applied for monitoring Hg 2+ ions in living LNCaP cells., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A new ratiometric probe composed of a dansyl-rhodamine dyad for the detection of Hg 2+ via fluorescence resonance energy transfer was designed and synthesized. Rhodamine, dansyl chloride, and hydrazide were selected as the acceptor, donor, and reaction site, respectively. It displayed high selectivity and sensitivity to Hg 2+ with obvious colour change and fluorescence change due to Hg 2+ -assisted hydrolysis of rhodamine hydrazide. A good linear relationship ranging from 0 to 16 μM and 0-28 μM for the Hg 2+ concentration was found based on absorbance and fluorescence assay, respectively. Detection limits of absorbance and fluorescence for Hg 2+ were calculated to be 1.22 μM and 9.10 μM, respectively., (© 2019 John Wiley & Sons, Ltd.)

Polyamines are involved in the regulation of many cellular functions and are promising biomarkers of numerous physiological conditions. Since the concentrations of these compounds in biological fluids are low, sample extraction is one of the most critical steps of their analysis. Here, we developed a comprehensive, sensitive, robust, and high-throughput LC-MS/MS stable-isotope dilution method for the simultaneous determination of 19 metabolites related to polyamine metabolism, including polyamines, acetylated and diacetylated polyamines, precursors, and catabolites from liquid biopsies. The sample extraction was optimized to remove interfering compounds and to reduce matrix effects, thus being useful for large clinical studies. The method consists of two-step liquid-liquid extraction with a Folch extraction and ethyl acetate partitioning combined with dansyl chloride derivatization. The developed method was applied to a small gender-related trial concerning human serum and urine samples from 40 obese subjects. Sex differences were found for cadaverine, putrescine, 1,3-diaminopropane, γ-aminobutyric acid, N8-acetylspermidine, and N-acetylcadaverine in urine; N1-acetylspermine in serum; and spermine in both serum and urine. The results demonstrate that the developed method can be used to analyze biological samples for the study of polyamine metabolism and its association with human diseases.

The abnormal location or generation of superoxide radical anion (O 2 •- ) are implicated in many diseases, including cancers; thus, development of an efficient method to detect O 2 •- is of great importance. Inspired by the fluorophore-governed selective manner to O 2 •- and peroxynitrite (ONOO - ) of previously reported phosphinate-based fluorescence probes, in this contribution, a phosphinothioate-containing probe, TPP , was designed. The probe exhibited easy accessibility through a one-step sequence and good photostability and biocompatibility. Interestingly, TPP showed high specificity and sensitivity to O 2 •- over other reactive oxygen species/nitrogen species including ONOO - . Furthermore, with the assistance of two-photon microscopy, TPP was successfully applied for imaging endogenous O 2 •- in live cells and tissues.

Human zinc-α2-glycoprotein (ZAG) is a 42 kDa adipokine which regulates body fat mass and is associated with cachexia and obesity. ZAG belongs to the major histocompatibility complex class I protein family and binds long-chain polyunsaturated fatty acids in its groove formed from the α1 and α2 domains. To identify the molecular basis of its lipid-binding function, we determined the first crystal structure at 2.49 Å resolution for fatty acid-bound ZAG, where the ligand was the fluorescent 11-(dansylamino)undecanoic acid (DAUDA). The 192 kDa crystallographic asymmetric unit contained six ZAG and eight fatty acid molecules in unique conformations. Six fatty acid molecules were localised to the ZAG grooves, where their tails were bound in two distinct conformations. The carboxylate groups of three fatty acids projected out of the groove, while the fourth was hydrogen bonded with R73 inside the groove. Other ligand-residue contacts were primarily hydrophobic. A new fatty acid site was revealed for two further DAUDA molecules at the ZAG α3 domains. Following conformational changes from unbound ZAG, the α3 domains formed tetrameric β-barrel structures lined by fatty acid molecules that doubled the binding capacity of ZAG. Analytical ultracentrifugation revealed that ZAG in solution was a monomer in the absence of DAUDA, but formed small amounts of tetramers with DAUDA. By showing that ZAG binds fatty acids in different locations, we demonstrate an augmented mechanism for fatty acid binding in ZAG that is distinct from other known fatty acid binding proteins, and may be relevant to cachexia., (© 2019 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.)

This paper describes a new fluorescent chemosensor (DSH) based on dipeptide conjugated with dansyl group, which was synthesized by solid phase peptide synthesis (SPPS) technology. DSH exhibited a highly selective and sensitive toward Zn 2+ ions by "turn-on" response based on generation of monomer-excimer mechanism in aqueous solutions, and the detection limit was calculated at 11.2 nM. In addition, the reversible of DSH-Zn with Na 2 EDTA establishes the reuse of DSH, and the circulation effect was very good. Moreover, DSH had good water solubility, and was successfully applied to bioimage intracellular Zn 2+ ions and Na 2 EDTA in two different living cells with exciting cellular permeability and low cytotoxicity, which indicated that DSH had great potential in the application of biological imaging., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Chemical isotope labeling (CIL) LC-MS is a highly sensitive and quantitative method for metabolome analysis. Because of a large number of peaks detectable in a sample and the need of running many samples in a metabolomics project, any significant change in mass measurement accuracy during the whole period of running samples can adversely affect the downstream peak alignment and quantitative analysis. Herein, we report a rapid method to check the mass accuracy of individual spectra in each CIL LC-MS run in order to flag up any run containing spectra with accuracy drift that falls outside the expected error. The flagged run may be re-run or discarded before merging with other runs for peak alignment and analysis. This method is based on the observation that some background signals are commonly detected in almost all spectra collected in CIL LC-MS runs. A mass accuracy check (MAC) software program has been developed to first find the common background mass peaks and then use them as mass references to calculate any mass shifts over the course of multiple sample runs. Using a metabolome dataset of 324 human cerebrospinal fluid (CSF) samples and 35 quality control (QC) samples produced by CIL LC-MS, we show that this accuracy check method can streamline the initial raw data processing for downstream analysis in metabolomics.

The present study investigated the separation of bicyclic β-amino acids with bicyclo[2.2.2]octane, bicyclo[3.1.1]heptane and cyclopenta[d][1,2]oxazole core structures by capillary electrophoresis using native cyclodextrins as well as neutral and charged derivatives as chiral selectors. The amino acids were derivatized with dansyl chloride to provide a UV chromophore. Separations were carried out at 20°C in a 48.5/40 cm, 50 µm fused-silica capillary at an applied voltage of 20 kV. Fifty millimolar sodium phosphate background electrolytes pH 2.5 and 7.2 containing either 5 or 30 mg/mL of the CDs were used. For the majority of the investigated CDs, enantioseparations could only be achieved at pH 2.5 when the analytes are positively charged. Successful enantioseparations as negatively charged analytes at pH 7.2 were only observed for few compounds. In the case of methyl-γ-cyclodextrin, opposite enantiomer migration order was observed in pH 2.5 or 7.2 background electrolytes. Dependence of the enantiomer migration order on the size of the cavity of the cyclodextrins was also found. Furthermore, the degree of methylation of β-cyclodextrin derivatives affected the migration order of several analyte enantiomers., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hydrogen sulfide (H2S) has been reported as a gaseous signaling molecule in cells. H2S modulation is dependent on the partial pressure of oxygen in cells, which means hypoxia can induce H2S production under various pathophysiological conditions. Hypoxia is a common condition in solid tumors and can lead to malignant tumors that may become aggressive and result in worse prognosis. We designed and synthesized probe Cu-CD for H2S detection under hypoxia conditions. It is selective and sensitive toward various biological thiols, reactive nitrogen species (RNS), and reactive oxygen species (ROS). The fluorescence intensity of Cu-CD in the cytoplasms of HeLa and EMT6 cells was enhanced in proportion to the concentration of exogenous/endogenous H2S. Moreover, Cu-CD can be able to detect endogenous H2S production accompanied by expression of HIF-1α. Therefore, Cu-CD can be a key tool to explore how H2S contributes to neovascularization and growth of solid tumor tissues in pathophysiological or hypoxic conditions.

The presence of potential carcinogen 4(5)-Methylimidazole (4-MeI) in foods causes much concern, stressing the need of a sensitive determination means. Here, we proposed a high-sensitivity method to determine 4-MeI in biscuits using dansyl chloride derivatization and disperse liquid-liquid micro-extraction (DLLME) followed by a liquid chromatography-ion trap mass spectrometry (LC-IT-MS) analysis. This developed method was subsequently compared to the solid phase extraction combining with liquid chromatography-triple quadrupole mass spectrometry (SPE-LC-QqQ-MS) method. The optimized derivatization conditions were 30 °C and 10 min. Results suggested that the column retention time (RT) was significantly extended, and the MS signal response of 4-MeI-dansyl derivative was also amplified. The developed DLLME-LC-IT-MS method in 4-MeI determination provided satisfactory linearity in a range of 0.5-300 ng/mL (R 2 > 0.9991), inter-day accuracy (87-102%) and precision (%RSD ≤ 13.6%) with the quantification limit of 0.2 ng/mL, which obtained similar results comparing to the conventional SPE-LC-QqQ-MS method., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The development of a simple, rapid and sensitive sensor to detect copper ion is very important for environmental detection. Here, we constructed a fluorescence biosensor based on fluorescence resonance energy transfer (FRET) between copper resistance operon coded protein C (CopC), a copper binding protein, and dansyl chloride (DNS-Cl) to selectively detect copper ion. At alkaline conditions, DNS-Cl was contently attached to CopC forming biosensor of DNS-Cl/CopC, in which fluorescence emission of CopC at 320nm was absorbed by DNS-Cl. After binding with copper ion, the fluorescence of DNS-Cl was quenched significantly to 47%. Within the range of 0.04-11μM (R=0.989), the good linearity was obtained and the detection limit reached to 7nM. More importantly, the biosensor of DNS-Cl/CopC has been successfully used to detecting of copper ion level in purified water, tap water and waste water drained from steel mill. And the results were consistent well with those obtained from the inductively coupled plasma mass spectrometry. Therefore, the established biosensor DNS-Cl/CopC is a creditable method to detect copper ion with high sensitivity and selectivity, which can be utilized as a powerful tool to monitor copper pollution in the environments., (Copyright © 2019. Published by Elsevier B.V.)

In this study, we report a sequential and reversibility fluorescent probe (DP5) based on pentapeptide conjugated with dansyl groups using the solid phase peptide synthesis (SPPS) technology. DP5 showed immediate "turn off" response toward Cu 2+ ions at an excitation wavelength of 330 nm with detection limits of 23.5 nM. The 2:1 binding ratio between DP5 and Cu 2+ were confirmed using Job's plot method and fluorescence titration study, and DP5-Cu complex was observed with an association constant of 6.76 × 10 8  M -2 . As designed, DP5-Cu complex as a promising analytical probe exhibited highly selective for H 2 S detection in aqueous solutions. The detection limit for H 2 S was obtained to be 17.2 nM, and lower than EPA and WHO guidelines. In addition, the reversibility and cyclicity were imparted to the DP5 during the detection of Cu 2+ and H 2 S, and cycle effect is very good. Furthermore, DP5 displayed better biocompatibility and low biotoxicity, and sequential fluorescence "on-off-on" responses of DP5 to Cu 2+ and H 2 S were successfully applied in two different living cells., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Nowadays, it is of great significance to develop a novel fluorescent chemosensor for Cd(II) ions detection with cost-effective, rapid, facile and applicable to environment and biological milieus. Herein, we report a new peptide-based fluorescent chemosensor DSC (Dan-Ser-Cys-NH 2 ) based on dipeptide (Ser-Cys-NH 2 ) conjugated with dansyl group, which was synthesized using solid phase peptide synthesis (SPPS) technology. As designed, DSC exhibited fluorescent "turn-on" response for Cd 2+ in 100% aqueous solution over a wide range of pH values based on photoinduced electron transfer (PET). The stoichiometry binding of DSC and Cd 2+ was determined to be 2:1 by Job's plot and ESI-MS analysis. Furthermore, DSC showed highly sensitive for Cd 2+ and a low detection limit of 13.8 nM. What's more, DSC has cell permeability and low cytotoxicity, and fluorescence imaging experiments demonstrated that DSC was capable of monitoring Cd 2+ in living HK2 cells by confocal microscopy., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Many indomethacin amides and esters are cyclooxygenase-2 (COX-2)-selective inhibitors, providing a framework for the design of COX-2-targeted imaging and cancer chemotherapeutic agents. Although previous studies have suggested that the amide or ester moiety of these inhibitors binds in the lobby region, a spacious alcove within the enzyme's membrane-binding domain, structural details have been lacking. Here, we present observations on the crystal complexes of COX-2 with two indomethacin-dansyl conjugates (compounds 1 and 2) at 2.22-Å resolution. Both compounds are COX-2-selective inhibitors with IC 50 values of 0.76 and 0.17 μm, respectively. Our results confirmed that the dansyl moiety is localized in and establishes hydrophobic interactions and several hydrogen bonds with the lobby of the membrane-binding domain. We noted that in both crystal structures, the linker tethering indomethacin to the dansyl moiety passes through the constriction at the mouth of the COX-2 active site, resulting in displacement and disorder of Arg-120, located at the opening to the active site. Both compounds exhibited higher inhibitory potency against a COX-2 R120A variant than against the WT enzyme. Inhibition kinetics of compound 2 were similar to those of the indomethacin parent compound against WT COX-2, and the R120A substitution reduced the time dependence of COX inhibition. These results provide a structural basis for the further design and optimization of conjugated COX reagents for imaging of malignant or inflammatory tissues containing high COX-2 levels.

A one-component array-based sensor consisting of a dansyl-modified polylysine (PLL-Dnc) is capable of discriminating the types and compositional ratios of human cells using varying buffer conditions. The PLL-Dnc sensor array, which affords turn-on fluorescence responses against analyte cells that depend on the pH value and the ionic strength, generates differential fluorescence signatures of cells and successfully discriminates eight types of human cell lines (2.0 × 10 4 cells/mL) with 100% accuracy using multivariate analysis. The array also allows differentiation of the composition of the cell mixtures that contain cells with the same tissue origin but of different subtypes. The good discrimination ability and simple platform of our "one-component"-based array allows an easy and rapid sensing of cells without requiring any information on specific biomarkers.

Metabolomics is considered an effective approach for understanding metabolic responses in complex biological systems. Accordingly, it has attracted increasing attention for biomarker discovery, especially in cancer. In this study, we used a non-invasive method to evaluate four urine metabolite biomarker candidates-o-phosphoethanolamine, 3-amio-2-piperidone, uridine and 5-hydroxyindoleactic acid-for their potential as bladder cancer diagnostic biomarkers. To analyze these targeted amine- and phenol-containing metabolites, we used differential 12 C 2 -/ 13 C 2 -dansylation labeling coupled with liquid chromatography/tandem mass spectrometry, which has previously been demonstrated to exhibit high sensitivity and reproducibility. Specifically, we used ultra-performance liquid chromatography (UPLC) coupled with high-resolution Fourier transform ion-cyclotron resonance MS system (LC-FT/MS) and an ion trap MS with MRM function (LC-HCT/MS) for targeted quantification. The urinary metabolites of interest were well separated and quantified using this approach. To apply this approach to clinical urine specimens, we spiked samples with 13 C 2 -dansylatedsynthetic compounds, which served as standards for targeted quantification of 12 C 2 -dansylated urinary endogenous metabolites using LC-FT/MS as well as LC-HCT/MS with MRM mode. These analyses revealed significant differences in two of the four metabolites of interest-o-phosphoethanolamine and uridine-between bladder cancer and non-cancer groups. O-phosphoethanolamine was the most promising single biomarker, with an area-under-the-curve (AUC) value of 0.709 for bladder cancer diagnosis. Diagnostic performance was improved by combining uridine and o-phosphoethanolamine in a marker panel, yielding an AUC value of 0.726. This study confirmed discovery-phase features of the urine metabolome of bladder cancer patients and verified their importance for further study., (Copyright © 2019. Published by Elsevier Taiwan LLC.)