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Flavonoids have emerged to be an important molecular frame for chemical sensors, due to their capability to give dual emission and their compatibility to biological cells. Two flavonoid compounds with Me 2 N- and Et 2 N-substituents were examined by acquiring their fluorescence at different temperatures, in order to evaluate the impact of intramolecular charge transfer (ICT) on ESIPT. By freezing the sample solution in liquid N 2 , the study detected the "locally excited" state at λ em ≈ 460 nm, in which both ICT and ESIPT processes were not present. As temperature was warmed up (to about -90 °C), ICT process became gradually allowed and emission was shifted to λ em ≈ 510 nm, which was attributed to the normal form N* of flavonoid. Emission from tautomeric form T* (λ em ≈ 575 nm) could only be observed at a higher temperature, when ESIPT became allowed. With the aid of a model compound (without R 2 N-substituent) and computational study, the study led to improved understanding on the photophysical properties of flavonoid materials in general.

Near-infrared luminophores have many advantages in advanced applications, especially for structures without π-conjugation aromatic rings. However, the fabrication of red clusteroluminogens from nonconjugated polymers is still a big challenge, let alone the near-infrared clusteroluminogens. Here, we develop nonconjugated luminophores with full-spectrum from blue to near-infrared light (470 ~ 780 nm), based on color phenomenon of nonconjugated polyesters synthesized from the amine-initiated copolymerization of epoxides and cyclic anhydrides. We reveal that amines act as initiators attached to polymer chain ends. The formation of various amine-ester complexes in polyesters induces red to near-infrared light, conceptually, amine-ester complexed clusteroluminescence via intra/inter-chain charge transfer. Significantly, emission colors can be easily tuned by the contents and types of amines, microstructures of polyesters, and their concentration. This work provides a low-cost, scalable platform and strategy for the production of high-efficiency, multicolor luminescent materials. Near-infrared luminescence is useful for advance applications, but is challenging to achieve through clusteroluminescence. Here, the authors report the use of amine-initiated polyesters for amine-ester clusters with near-infrared emission. [ABSTRACT FROM AUTHOR]

Over-expression of glutathione S-transferase (GST) can promote Cisplatin resistance in hepatocellular carcinoma (HCC) treatment. Hence, inhibiting GST is an attractive strategy to improve Cisplatin sensitivity in HCC therapy. Although several synthesized GST inhibitors have been developed, the side effects and narrow spectrum for anticancer seriously limit their clinical application. Considering the abundance of natural compounds with anticancer activity, this study developed a rapid fluorescence technique to screen "green" natural GST inhibitors with high specificity. The fluorescence assay demonstrated that schisanlactone B (hereafter abbreviated as C1) isolated from Xue tong significantly down-regulated GST levels in Cisplatin-resistant HCC cells in vitro and in vivo. Importantly, C1 can selectively kill HCC cells from normal liver cells, effectively improving the therapeutic effect of Cisplatin on HCC mice by down-regulating GST expression. Considering the high GST levels in HCC patients, this compound demonstrated the high potential for sensitizing HCC therapy in clinical practice by down-regulating GST levels. [Display omitted] • Designed a visual fluorescent probe PM for the rapid screening GST natural inhibitors. • The natural and "green" GST inhibitor C1 showed high safety to normal liver cells but high toxicity to HCC cells. • The inhibitor C1 demonstrated an excellent sensitizing effect on Cisplatin-resistant and sensitive HCC. [ABSTRACT FROM AUTHOR]

Objective To evaluate the bio-safety of graphene quantum dots (GQDs), we studied its effects on the embryonic development of zebrafish. Methods In vivo , biodistribution and the developmental toxicity of GQDs were investigated in embryonic zebrafish at exposure concentrations ranging from 12.5-200 μg/mL for 4-96 h post-fertilization (hpf). The mortality, hatch rate, malformation, heart rate, GQDs uptake, spontaneous movement, and larval behavior were examined. Results The fluorescence of GQDs was mainly localized in the intestines and heart. As the exposure concentration increased, the hatch and heart rate decreased, accompanied by an increase in mortality. Exposure to a high level of GQDs (200 μg/mL) resulted in various embryonic malformations including pericardial edema, vitelline cyst, bent spine, and bent tail. The spontaneous movement significantly decreased after exposure to GQDs at concentrations of 50, 100, and 200 μg/mL. The larval behavior testing (visible light test) showed that the total swimming distance and speed decreased dose-dependently. Embryos exposed to 12.5 μg/mL showed hyperactivity while exposure to higher concentrations (25, 50, 100, and 200 μg/mL) caused remarkable hypoactivity in the light-dark test. Conclusion Low concentrations of GQDs were relatively non-toxic. However, GQDs disrupt the progression of embryonic development at concentrations exceeding 50 μg/mL. [ABSTRACT FROM AUTHOR]

Arabidopsis cryptochrome 2 (CRY2) is a blue-light receptor mediating blue-light inhibition of hypocotyl elongation and photoperiodic promotion of floral initiation. CRY2 is a constitutive nuclear protein that undergoes blue-light-dependent phosphorylation, ubiquitination, photobody formation, and degradation in the nucleus, but the relationship between these blue-light-dependent events remains unclear. It has been proposed that CRY2 phosphorylation triggers a conformational change responsible for the subsequent ubiquitination and photobody formation, leading to CRY2 function and/or degradation. We tested this hypothesis by a structure-function study, using mutant CRY2–GFP fusion proteins expressed in transgenic Arabidopsis. We show that changes of lysine residues of the NLS (Nuclear Localization Signal) sequence of CRY2 to arginine residues partially impair the nuclear importation of the CRY2K541R and CRY2K554/5R mutant proteins, resulting in reduced phosphorylation, physiological activities, and degradation in response to blue light. In contrast to the wild-type CRY2 protein that forms photobodies exclusively in the nucleus, the CRY2K541R and CRY2K554/5R mutant proteins form protein bodies in both the nucleus and cytosol in response to blue light. These results suggest that photoexcited CRY2 molecules can aggregate to form photobody-like structure without the nucleus-dependent protein modifications or the association with the nuclear CRY2-interacting proteins. Taken together, the observation that CRY2 forms photobodies markedly faster than CRY2 phosphorylation in response to blue light, we hypothesize that the photoexcited cryptochromes form oligomers, preceding other biochemical changes of CRY2, to facilitate photobody formation, signal amplification, and propagation, as well as desensitization by degradation. [ABSTRACT FROM PUBLISHER]

Abstract: Methods for real time, highly selective and sensitive polynucleotide detection are of vast scientific and economic importance. Fluorescence resonance energy transfer (FRET)-based assays which take advantage of the collective response of water-soluble conjugated polymers (CPs) and the self-assembly characteristic of aqueous polyelectrolytes have been widely used for the detection of DNA, RNA, protein and small molecules. The detection sensitivity of CP-based biosensor is dependent on the signal amplification of dye emission upon excitation of CP relative to that upon direct excitation of the dye. Using cationic polyfluorene derivatives and chromophore (fluorescein or Texas Red) labeled single-stranded DNA molecules (ssDNA-C*) as donor/acceptor pairs, we show that in addition to the spectral overlap, orientation and distance between the donor and the acceptor, the energy levels and fluorescence quenching of the donor/acceptor within the polymer/DNA-C* complexes are also important factors that affect the signal output of dye emission. [Copyright &y& Elsevier]

Brown carbon (BrC) has been proposed as an important driving factor in climate change due to its light absorption properties. However, our understanding of BrC's chemical and optical properties are inadequate, particularly at remote regions. This study conducts a comprehensive investigation of BrC aerosols in summer (Aug. 2013) and winter (Jan. 2014) at Southeast Tibetan Plateau, which is ecologically fragile and sensitive to global warming. The concentrations of methanol-soluble BrC (MeS-BrC) are approximately twice of water-soluble BrC (WS-BrC), demonstrating the environmental importance of water-insoluble BrC are previously underestimated with only WS-BrC considered. The mass absorption efficiency of WS-BrC (0.27–0.86 m2 g−1) is lower than those in heavily polluted South Asia, indicating a distinct contrast between the two sides of Himalayas. Fluorescence reveals that the absorption of BrC is mainly attributed to humic-like and protein-like substances, which broaden the current knowledge of BrC's chromophores. Combining organic tracer, satellite MODIS data and air-mass backward trajectory analysis, this study finds BrC is mainly derived from bioaerosols and secondary formation in summer, while long-range transport of biomass burning emissions in winter. Our study provides new insights into the optical and chemical properties of BrC, which may have implications for environmental effect and sources of organic aerosols. Image 1 • Methanol-soluble BrC is more abundant than water-soluble BrC. • Protein- and humic-like substances are the main chromophores in BrC. • BrC is mainly derived from bioaerosols and secondary formations in summer. • In winter, biomass burning emissions are the dominant sources of BrC. Optical properties and organic tracers demonstrate that BrC is derived from bioaerosols in summer, while biomass burning emissions in winter. [ABSTRACT FROM AUTHOR]

Mung bean nuclease is a single stranded specific DNA and RNA endonuclease purified from mung bean sprouts. It yields 5′-phosphate terminated mono- and oligonucleotides. The activity level of this nuclease can act as a marker to monitor the developmental process of mung bean sprouts. In order to facilitate the activity and physiological analysis of this nuclease, we have developed a biosensing assay system based on the mung bean nuclease-induced single-stranded DNA scission and the affinity difference of graphene oxide for single-stranded DNA containing different numbers of bases. This end-point measurement method can detect mung bean nuclease in a range of 2×10 −4 to 4×10 −2 with a detection limit of 1×10 −4 unit/mL. In addition, we demonstrate the utility of the assay for screening chemical antibiotics and metal ions, resulting in the identification of several inhibitors of this enzyme in vitro . Furthermore, we firstly report that inhibiting mung bean nuclease by gentamycin sulfate and kanamycin in vivo can suppress mung bean sprouts growth. In summary, this method provides an alternative tool for the biochemical analysis for mung bean nuclease and indicates the feasibility of high-throughput screening specific inhibitors of this nuclease in vitro and in vivo . [ABSTRACT FROM AUTHOR]

Abstract: Five new coordination polymers, {[Cd3(bpt)2(DMF)2]·(H2O)2} n (1), [Cd(Hbpt)(bipy)0.5(H2O)] n (2), [Cd2(bpt)(phen)2Cl] n (3), {[Cu2(bpt)(phen)(μ2–OH)(H2O)]·(H2O)2} n (4) and {[Mn5(Hbpt)4(phen)4(μ2–OH)2(H2O)2]·(H2O)2(CH3CN)2} n (5) have been prepared through hydro(solvo)thermal reactions of H3bpt (H3bpt=biphenyl-3,4′,5-tricarboxylic acid) with different pyridyl-containing auxiliary ligands (bipy=4,4′-bipyridine and phen=1,10-phenanthroline). Compound 1 represents a 3D ladder-like framework composed of rod-shaped infinite chains. In 2, the bridging ligand bipy links binuclear cadmium ions to generate a 2D layer. Compound 3 features a 1D ladder structure and further linked by π–π stacking interaction to form a 3D supramolecular network. Compound 4 exhibits a binodal 3-connected net which features the Schlafli symbol of (4·82). Compound 5 contains trimetallic cluster and binuclear unite which are further linked by Hbpt ligand to form a 2D layer. Moreover, photoluminescent properties of compounds 1–3 were studied in the solid state. Magnetic susceptibility measurements indicate that compound 4 exhibits ferromagnetic exchange interactions, whereas compound 5 displays antiferromagnetic exchange interactions. [Copyright &y& Elsevier]

Exosomes (Exos) of approximately 30–150 nm in diameters are the promising vehicles for therapeutic drugs. However, several challenges still exist in clinical applications, such as unsatisfied yield of exosomes, complicated labeling procedure and low drug loading efficiency. In this work, the gram-scale amount of high-purity urinary exosomes can be obtained from gastric cancer patients by non-invasive method. Passion fruit-like Exo-PMA/Au-BSA@Ce6 nanovehicles were fabricated by considerable freshly-urinary Exos loaded efficiently with multi-functionalized PMA/Au-BSA@Ce6 nanoparticles via instant electroporation strategy. In this system, prepared Exo-PMA/Au-BSA@Ce6 nanovehicles could be internalized into cancer cells effectively, and could delay the endocytosis of macrophages and prolong blood circulation time owing to its membrane structure and antigens. Under 633 nm laser irradiation and acidic condition, the structures of nanovehicles would be collapsed and tremendous PMA/Au-BSA@Ce6 nanoparticles could be released inside cancer cells, produced considerable singlet oxygen, inhibiting growth of tumor cells. In vivo experiment of MGC-803 tumor-bearing nude mice showed that prepared Exo-PMA/Au-BSA@Ce6 nanovehicles could target tumor cells with deep penetration and superior retention performance in tumors. This work reports a reliable conjugation-free labeling strategy for tracking exosomes harvested from human urine. Moreover, the integration of multifunctional nanoparticles with urinary Exos paves a versatile road for the development of cancer-targeted photodynamic therapy. [ABSTRACT FROM AUTHOR]