Near-infrared fluorescent probe with large Stokes shift for specific detection of lysine.

A new near-infrared (NIR) fluorescent probe CL based on coumarin- dicyanoisophorone was synthesized. Addition of Lys to probe CL solution in DMF/H2O (9:1, v/v) medium resulted in noticeable enhancement in the intensity of the fluorescence emission at 702 nm, accompanying distinct color change from yellow to pink. While addition of other amino acids and biothiols (Gly, Hcy, GSH, Glu, Val, Tyr, Arg, Trp, Lys, His, Leu, Phe, Asp and Met) did not bring about substantial changes in both fluorescence emission and color. The detection limit was calculated to be 0.51 µM. Job's plot test revealed that probe CL and Lys formed a complex of 1:1 stoichiometry. Probe CL showed high stability and could be used to recognize Lys in a wide pH range of 4.0-10.0. The sensing mechanism was proposed and verified by 1H NMR spectral measurement. The dual-modal fluorescence turn-on and colorimetric NIR probe with an extremely large Stokes shift of 280 nm may be utilized for highly specific and practical sensing of Lys.

Selective and Sensitive Detection of Hg2+ and Ag+ by a Fluorescent and Colorimetric Probe with Large Stokes Shift.

Development of fluorescent sensors with large Stokes shift for selective detection of heavy metals is of great importance. A novel fluorescent probe with extremely large Stokes shift (212 nm) was synthesized for selective and simultaneous detection of Hg2+ and Ag+ ions. The deep yellow probe turned colorless or pale yellow after addition of Hg2+ or Ag+. The new probe could be utilized for absorption spectral detection of Hg2+ and Ag+ both in ethanol and aqueous solution. Addition of Hg2+ and Ag+ ions caused significant decrease in the fluorescence intensity of the new probe and the selective recognition of Hg2+ and Ag+ was not interfered by common competitive metal ions including Li+, Na+, K+, Cu2+, Fe2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Ca2+, Mg2+, Al3+, Cr3+ and Fe3+. The detection limit for Hg2+ and Ag+ was calculated to be 4.68 µM and 4.29 µM, respectively. Application of the new probe for quantitative determination of Hg2+ and Ag+ concentrations in real water samples was accomplished.

Highly selective and sensitive detection of Hg2+ by a novel fluorescent probe with dual recognition sites.

A novel thionocarbonate-coumarin-thiourea triad-based probe with dual recognition sites for sensing mercury (Hg2+) ion was developed. The synthesized probe possessed both fluorogenic ("off-on") and chromogenic (from colorless to blackish brown) sensing performance towards Hg2+ ions. The fluorescence intensity was increased by 70 fold after the addition of Hg2+. As expected, the probe exhibited excellent selectivity and sensitivity for Hg2+ compared to other common competitive metal ions. The fluorescence intensity of the probe improved linearly with the increase of the concentration of Hg2+ (0-40 µM). Also, the minimum limit of detection (LOD) of the synthesized probe was 0.12 µM. Considering the importance of test feasibility in the harsh environment, the developed probe was applicable for detecting Hg2+ ions over a broad working pH range of 3-11. It is reliable and qualifies for the quantitative determination of Hg2+ concentrations in actual water samples. Finally, the probe achieved the bioimaging performance of Hg2+ in living cells and plants with good biocompatibility.

A New Spiropyran-Based Fluorescent Probe for Dual Sensing of Ferrous Ion and pH.

A new spiropyran-based fluorescent probe was developed for dual detection of Fe2+ ion and pH. Addition of Fe2+ and Ag+ to the probe solution enhanced the fluorescence intensity by 6 and 5 fold, respectively. Addition of Fe3+, Hg2+ and Ni2+ caused slight increase in the fluorescence intensity of the probe. While addition of other common metal ions did not bring about substantial change of the fluorescence. Thus the probe can be used for fluorescence turn-on detection of Fe2+ ion in ethanol/water (9:1) medium. The detection limit of the probe for Fe2+ is 0.77 µM. The suitable pH range for the probe to detect Fe2+ was pH 3 - 9. Other metal ions including Li+, Na+, K+, Ag+, Cu2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Hg2+, Ca2+, Mg2+, Al3+, Cr3+, and Fe3+ did not cause marked interference with Fe2+ recognition. The color of the probe solution was yellow at pH 1 - 2 and colorless at other pH values. The fluorescence intensity of the probe was low at pH 1 - 12 and increased significantly when the pH was 13 and 14, indicating that the probe can be used as a colorimetric and fluorescent probe for sensing extremely acidic or extremely alkaline conditions through different channels.

Ultrasensitive and selective fluorescent sensor for cysteine and application to drug analysis and bioimaging.

A fluorescent sensor based on coumarin-maleimide conjugate was developed for efficient discrimination of Cys from Hcy and GSH in both organic and aqueous solution. Addition of Cys to the non-fluorescent sensor solution in DMF induced bright blue fluorescence and enhanced the fluorescence intensity by 320-fold while other amino acids and biothiols (Gly, Hcy, GSH, Glu, Val, Tyr, Arg, Trp, Lys, His, Leu, Phe, Asp and Met) did not bring about remarked change. The sensor responds to Cys extremely rapidly. If Cys was added to the sensor solution, the fluorescence intensity increased by 170-fold immediately and attained the maximum value in 5 min. A linear relationship was observed between Cys concentration within 2-20 µM and the fluorescence intensity of the sensor solution. The detection limit of the sensor toward Cys is as low as 4.7 nM. The sensor is also effective for specific detection of Cys in aqueous (DMF/H2O = 9:1, v/v) solution. Practical application of the sensor to drug analysis and bioimaging of living Hela cells has been verified. Possible sensing mechanism of the sensor toward Cys has been proposed.

[Regional Air Pollution Process in Winter over the Yangtze River Delta and Its Influence on Typical Northern Cities].

In this study, we analyzed several pollution episodes that occurred in the autumn and winter of 2018-2019 using multiple methods including the hierarchical clustering analysis, backward trajectory, and potential source contribution analysis based on monitored air quality and meteorological data. Bengbu, being a representative city to the north of the Yangtze River Delta (YRD) region and located in a heavily polluted area during these two pollution processes, is the focus of this work. The results indicated that the northern part of the YRD region is affected because of unfavorable meteorological conditions such as weak ground pressure, high humidity, low temperature, low wind speeds, and regional transport. The regional pollution processes over the YRD region in the autumn and winter seasons exhibit characteristics of wide influence and long duration with mainly two types of pollution:regional transport and intra-regional accumulation. During the two selected pollution episodes, the average PM2.5 concentration in the northern YRD region reached 131.6 µg·m-3 and 115.4 µg·m-3, respectively. The former type had a shorter duration but exhibited rapid accumulation of pollutants in a short period of time with greater pollution intensity, wider pollution range, and deeper pollution intrusion. Qualitative and quantitative analysis of the potential sources of PM2.5 based on PSCF and CWT showed that the PM2.5 concentration during EP1 was due to transport from cities such as Linyi, Xuzhou, Suqian, and Lianyungang to the pollution trajectory. The CWT value generally exceeded 80 with the highest value near 200. In contrast, EP2 was affected by the neighboring cities such as Suqian, Suzhou, and Xuzhou, and the CWT value was over 60 with the highest approaching 160, indicating that the interaction among cities in the study area is significant. This study shows that cross-regional air pollution control strategies are particularly important for alleviating the pollution situation in the northern part of the YRD region.

A novel bifunctional fluorescent and colorimetric probe for detection of mercury and fluoride ions.

A fluorescent and colorimetric probe L1 based on a simple coumarin derivative for detection of Hg2+ and F- ions was developed. Upon addition of Hg2+ and F- ions, L1 underwent desulfurization and desilylation, respectively, to induce marked increase in the fluorescence intensity and sharp color change from light yellow to dark purple and light brown, respectively. Probe L1 could be used for sensing and for quantitative measurement of Hg2+ and F- ions by both UV-vis and fluorescence spectra. The bifunctional probe exhibited a high selectivity over other competitive cations and anions and could be used in both organic and aqueous media over a wide pH range.

1-[(4-Chloro-phen-yl)(phen-yl)meth-yl]piperazine-1,4-diium bis-(trichloro-acetate)-trichloro-acetic acid (1/1).

In the title salt adduct, C(17)H(21)ClN(2) (2+)·2C(2)Cl(3)O(2) (-)·C(2)HCl(3)O(2), the Cl atom of the dication is disordered over two positions in a 0.915 (3):0.085 (3) ratio. The Cl atoms in the trichloroacetate anions and trichloroacetic acid molecule are also disordered, with refined site-occupation factors of 0.59 (3):0.41 (3), 0.503 (12):0.417 (12) and 0.653 (12):0.347 (12). The piperazine ring adopts a chair conformation, with puckering parameters Q(T) = 0.587 (3) Å, θ = 2.6 (2) and Φ 334 (6)°. In the crystal, neighbouring mol-ecules are linked by N-H⋯O, O-H⋯O, N-H⋯Cl, C-H⋯O and C-H⋯Cl hydrogen bonds, forming a three-dimensional network.

4-[(4-Chloro-phen-yl)(phen-yl)-meth-yl]-piperazin-1-ium picrate monohydrate.

The asymmetric unit of the title compound, C(17)H(20)ClN(2) (+)·C(6)H(2)N(3)O(7) (-)·H(2)O, contains a piperazin-1-ium cation, a picrate anion and one solvent water mol-ecule. The piperazene ring is protonated at one N atom and adopts a highly distorted chair conformation with the chloro-pheny(phen-yl)methyl substituent on the second N atom in an equatorial position. The crystal structure is stabilized by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds.

Cinnarizinium picrate.

In the title salt {systematic name: 4-diphenyl-methyl-1-[(E)-3-phenyl-prop-2-en-1-yl]piperazin-1-ium 2,4,6-trinitro-pheno-late), C(26)H(29)N(2) (+)·C(6)H(2)N(3)O(7) (-), the cinnarizinium cation is protonated at the piperazine N atom connected to the styrenylmethyl group; the piperazine ring adopts a distorted chair conformaiton. In the crystal, bifurcated N-H⋯(O,O) hydrogen bonds link the components into two-ion aggregates.

Improved synthesis of mestranol and ethinyl estradiol (EE) related degradation products as authentic references.

Preparative chemical methods for the synthesis of 10 degradation or photodecomposition products of mestranol and ethinyl estradiol (EE) are described. The synthesized compounds are useful as reference materials and standards for pharmaceutical analysis of mestranol and EE as bulk chemical or in formulated product. New synthetic methods were presented and the known synthetic procedures were improved. Detailed structural characterization of the degradation or photodecomposition products of mestranol and EE and related compounds was reported.

17α-Ethynyl-3-methoxy-estra-1,3,5(10),9(11)-tetraen-17-ol.

In the title compound, C(21)H(24)O(2), rings B, C and D adopt half-chair, distorted half-chair and envelope conformations, respectively. In the crystal structure, there is an inter-molecular O-H⋯O hydrogen bond. The mol-ecules are arranged in a head-to-tail fashion, with the meth-oxy and hydr-oxy groups forming a two-dimensional hydrogen-bond network.

Methyl 3,4-O-isopropyl-idene-2-O-[(methyl-sulfan-yl)thio-carbon-yl]-ß-l-arabinoside.

In the title compound, C(11)H(18)O(5)S(2), the six- and five-membered rings adopt a chair and an approximately planar conformation, respectively.