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Abstract We reported a novel and readily synthesized fluorescent "turn-on" probe L (Dansyl-Glu-Pro-Gly-Cys) based on dansyl group combine tetrapeptide. The probe L exhibited highly sensitive fluorescent recognition to Cd2+ ions in HEPES buffer solutions (10.0 mM, pH 7.4). The 2:1 binding stoichiometry of L with Cd2+ were determined based on fluorescence titration and the Job's plot investigation. The competitive experiments were found to be highly selective for the Cd2+ ions even in the existence of excess competing metal ions including Zn2+, Pb2+, Hg2+ and Cu2+ ions. The binding constant of the complex L -Cd was calculated to be 5.18 × 1010 M−2, and showed great affinity compared to other probes. In addition, the detection limit of the probe L for Cd2+ ions was calculated to be 45 nM, which presented a pronounced sensitivity toward Cd2+ ions. Most importantly, the probe L had wide range of pH and good biocompatibility, and were successfully applied to selectively detected Cd2+ ions within pH range of 7–12 and bioimaging studies in live cells. Graphical Abstract Unlabelled Image Highlights • A novel fluorescent peptide-based probe (L) was synthesized. • L exhibited exclusively selective fluorescent "turn-on" response toward Cd2+ ions. • L displayed high sensitivity for Cd(II) with a low detection limit of 45 nM. • L could serve as a potential probe to detect Cd2+ ions in living cells. [ABSTRACT FROM AUTHOR]

The zinc ions (Zn 2+ ) play extremely irreplaceable role in the organism and the environment, the design and synthesis of a biomolecule-based fluorescence chemosensor for the detection of Zn 2+ with high sensitivity is very important. Herein, a novel tetrapeptide-based dansyl fluorescent “turn-on” response chemosensor ( L ) has been designed and synthesized by solid phase peptide synthesis (SPPS). As designed, L can detect Zn 2+ ions with specifically and sensitively based on photo-induced electron transfer (PET) mechanism in 100% aqueous solutions, and other metal ions do not interfere with Zn 2+ ions recognition. The stoichiometric ratio of L with Zn 2+ ions was 2:1, which matches with fluorescence titration and Job-plot assay. In addition, the reversibility and circularly process of the detection of L was confirmed by adding bonding agent Na 2 EDTA. Moreover, L exhibits excellent biocompatibility and low biotoxicity with the limit of detection (LOD) for Zn 2+ about 18 nM, and has been successfully utilized for fluorescence imaging of Zn 2+ ions in living HeLa cells under physiological conditions. [ABSTRACT FROM AUTHOR]

Theophylline, one of the most commonly used bronchodilators and respiratory stimulators for the treatment of acute and chronic asthmatic conditions, can cause permanent neurological damage through chronic or excessive ingestion. In this work, DFT calculation was performed to identify the metabolic mechanisms of theophylline by cytochrome P450 (CYP450) monooxygenase. Two main metabolic pathways were investigated, namely, N 1 - (path A) and N 3 - (path B) demethylations, which proceeded through N-methyl hydroxylation followed by the decomposition of the generated carbinolamine species. N-methyl hydroxylation involved a hydrogen atom transfer (HAT) mechanism, which can be generalized as the N-demethylation mechanism of xanthine derivatives. The energy gap between the low-spin double state (LS) and the high-spin quartet state (HS) was low (<1 kcal mol −1 ), indicating a two-state reactivity (TSR) mechanism. The generated carbinolamine species preferred to decompose through the adjacent heteroatom (O 6 for path A and O 2 for path B) mediated mechanism. Path B was kinetically more feasible than path A attributed to its relatively lower activation energy. 1-Methylxanthine therefore was the energetically favorable metabolite of theophylline. The observations obtained in the work were in agreement with the experimental observation, which can offer important implications for further pharmacological and clinic studies. [ABSTRACT FROM AUTHOR]

Mechanisms of photo‐catalytic decarboxylative reaction between 2‐phenylbutanoic acid and 1,4‐dicyanobenzene (1,4‐DCB) have been investigated with the method of M06‐L/ma‐def2‐TZVP in the domain‐decomposition COnductor‐like Screening MOdel (ddCOSMO) of CH3CN. The TDDFT calculations of 1,4‐DCB and 2‐phenylbutanoic acid model have revealed the photo‐excitation and electron transfer process, which could agree with experimental phenomena. The computational results of Gibbs free energy profiles show that the R1+1,4‐DCB model could achieve the decarboxylative reaction under the 300 nm UV light in path c. And paths a and b indicate that HPO42− and K2HPO4 could assist the whole reaction process with lower energy barrier successfully. Results would provide valuable insights into these types of interactions and related ones. [ABSTRACT FROM AUTHOR]

• A new peptide-based fluorescent probe DCH was synthesized. • DCH exhibited high sensitivity to Zn2+, with detection limits of 30.49 nM. • DCH was utilized for detecting Zn2+ in two real samples with high reliability. • DCH was low toxicity and could be used to monitor Zn2+ in two living cells. Zinc (Zn2+) ions play a very important role in the environment and organisms, and it is of great significance to realize the high sensitivity and selectivity detection of Zn2+ ions. Herein, a new peptide-based fluorescent probe named DCH was rationally designed and synthesized by solid phase peptide synthesis with Fmoc chemistry. DCH exhibited excellent fluorescent "turn-on" responding to Zn2+ with highly selective and exhilaratingly sensitive in aqueous media, with detection limits (LOD) as low as 30.49 nM. ESI-MS, Job's plot curves and fluorescence titration results indicated that the stoichiometric ratio between DCH and Zn2+ was 2:1. DCH could be regenerated by adding EDTA solutions to the complex formed during interaction, and indicated that DCH was promising reversibility probe. Furthermore, DCH has excellent practical application potential through two actual water sample experiments. Importantly, DCH was successfully used in monitor cellular Zn2+ and EDTA in living HK2 cells and SV-HUC-1 cells based on good biocompatibility and exciting low toxicity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel dual-functional probe FLH was developed. • FLH has ability to fast (response time <50 s) and sensitively (LOD = 1.5 nM) detect Cu2+. • FLH -Cu2+ complex displayed colorimetric and fluorescent response toward CN−. • FLH was successfully applied to detect Cu2+ and CN− in test strips and real samples. • FLH was almost no toxicity and successfully detected Cu2+ and CN− in living cells. A novel dual-functional peptide probe FLH based on fluorescent "on–off–on" strategy and colorimetric visualization method was designed and synthesized. This new probe exhibited highly selective and rapid detection of Cu2+ with significant fluorescent "turn-off" response, with a visible colorimetric change from yellow to orange. The combination ratio of FLH to Cu2+ (1:1) was determined using ESI-HRMS spectra and Job's plot. The fluorescent emission showed a good linear response (R2 = 0.9986) with a low detection limit of 1.5 nM. In addition, the FLH -Cu2+ complex displayed colorimetric changes and a fluorescent "off–on" response toward CN− over a wide pH range from 7 to 12. This detection behavior was observed within 20 s, with a limit of detection (LOD) for CN− at 12.7 nM. Based on stability and accuracy, FLH was next developed as dual-functional test strips, and was also successfully applied to detect Cu2+ and CN− in two actual water samples. More importantly, the cytotoxicity studies indicated that FLH had good biocompatibility and low toxicity, and was successfully utilized for monitoring Cu2+ and CN− in living cells through fluorescence imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fluorescent probe DSD based on the dipeptide receptor was synthesized. • DSD exhibited fluorescent quenching for Cu2+ and recovered rapidly by adding CN−. • The detection limit of 2.4 nM for Cu2+ and 41.9 nM for CN−. • DSD was successfully applied for detecting and imaging Cu2+ and CN− in live cells. A novel fluorescent probe (DSD) was reasonably designed and synthesized with dansyl-labeled dipeptide (Dan-Ser-Asp-NH 2). DSD featured remarkably large Stokes shift (230 nm) and perfect water solubility, and exhibited high selectivity and rapid recognition toward Cu2+ via fluorescence quenching. The detection limit of DSD for Cu2+ was 2.4 nM, indicated that DSD has excellent sensitivity. In addition, the stoichiometry between DSD and Cu2+ were detected as 1:1 by fluorescence titration, Job's plot and ESI-HRMS data. As designed, DSD -Cu2+ system was able to sequentially detect CN− according to the displacement approach with fluorescence "off–on" response, and the detection limit for CN− was calculated to be 41.9 nM. Specifically, the response time of DSD with Cu2+ and CN− was less than 40 s, which rendered it suitable for real time detection in actual water samples. In addition, with the alternate addition of Cu2+ and CN−, the reversible cycles could be repeated for at least 10 times, indicated that DSD was a promising reversibility probe. DSD showed low toxicity and good biocompatibility, and was successfully applied to detect Cu2+ and CN− in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel peptide fluorescent probe DGGH was synthesized. • DGGH -Cu2+ system showed highly selective and "turn-on" response to S2−. • The detection limit of DGGH -Cu2+ for sensing S2− was calculated to be 13.7 nM. • DGGH -Cu2+ was successfully applied to monitor Cu2+ and S2− in real samples and living cells. We report a new fluorescent probe named DGGH with dansyl-labeled tripeptide (Dan-Gly-Gly-His-NH 2). DGGH showed obvious fluorescence quenching after the addition of Cu2+ ions and a 1:1 ensemble system (DGGH -Cu2+) was formed, the limit of detection was 37.9 nM. As expected, DGGH -Cu2+ ensemble system exhibited high selectivity and rapid response for S2− in 100% aqueous solutions, as a result of the addition of S2− immediately replaced Cu2+ from the DGGH -Cu2+ ensemble system. The limit of detection of the DGGH -Cu2+ ensemble for S2− was determined to be 13.7 nM. In addition, DGGH -Cu2+ has excellent detection performance within a wide pH range of 6 to 12, and its outstanding response time of less than 50s. Furthermore, we demonstrated the usability of the present approach for detecting Cu2+ and S2− in two water samples. What's more, DGGH was successfully applied to monitor Cu2+ and S2− in living LNcap cells based on good cells permeability and low toxicity. [ABSTRACT FROM AUTHOR]

A new, structurally random perylene diimide (PDI) copolymer acceptor, PPDI , has been readily synthesized from Stille cross-coupling polycondensation of two pairs of regioisomeric dibromo-PDIs with 2,5-bis(trimethylstannyl)thiophene. PPDI possesses a complex structural configuration with a greatly twisted conformation, and thus exhibits weak intermolecular interactions. A solution of PPDI and a polymer donor such as PBT7-Th affords a smooth homogenous film without large crystalline domain formation. This composite film absorbs strongly throughout the visible spectrum, and when used as an active layer in all-polymer solar cells, provides a power conversion efficiency of over 5%. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fluorescent probe DAHK was synthesized based on copper peptide backbone. • DAHK could detect Cu2+ in 100 % aqueous medium with obvious fluorescence quenching. • DAHK-Cu2+ ensemble exhibited fluorescent "off–on" response with H 2 S. • DAHK was successfully used to selectively detect Cu2+ and H 2 S in living cells. • DAHK was successfully applied to sensitively detect Cu2+ and H 2 S in test strips. Copper ions (Cu2+) and hydrogen sulfide (H 2 S) detection is of great significance in environmental monitoring and disease screening. Herein, a novel fluorescent probe (DAHK) was rationally designed and easily synthesized based on a copper peptide backbone labelled a dansyl fluorophore. DAHK exhibited large Stokes shift (210 nm), high sensitivity (38.9 nM) and high selectivity response to Cu2+ ions based on obvious fluorescence quenching in HEPES buffer (10.0 mM, pH 7.4) solutions. In addition, the in situ formed DAHK -Cu2+ ensemble was successfully used as a secondary probe for rapidly and sequentially detected H 2 S via fluorescence "off–on" response, and without interference by a range of other anions. The limit of detection (LOD) for 47.3 nM was determined, which was a much lower value than WHO and EPA guidelines (H 2 S) for drinking water. The reversibility of interaction of DAHK with Cu2+ and H 2 S was monitored using fluorescence emission spectra. Cells imaging experiments exhibited that DAHK had good membrane permeability and excellent low toxicity. Moreover, DAHK was successfully made into fluorescent test strips for visual detection and rapid analysis based on the exciting stability and excellent water solubility. [ABSTRACT FROM AUTHOR]

The imidazo[2,1-b][1,3,4]thiadiazoles are converted to 2-(arylthio)-1H-imidazoles using aryl halides under Cu(acac)2-catalysis and microwave irradiation. [ABSTRACT FROM AUTHOR]