ortho‐Methyl effects are exploited to tune steric hindrance between side‐chain N,N′‐diaryls and polycyclic dihydrodibenzoa,cphenazine, and in turn control the conformations of ...N,N′‐diphenyl‐dihydrodibenzoa,cphenazine (DPAC) and its ortho‐methyl derivatives Mx‐My (x=0, 1 or 2, y=1 or 2, x and y correlate with the number of methyl groups in the ortho‐positiond of N,N′‐diphenyl). The magnitude of steric hindrance increases as x and y increase, and the V‐shaped dihydrodibenzoa,cphenazine skeleton is gradually tuned from a bent (DPAC) to planar (M2‐M2) structure in the ground state. As a result, the relaxation of the excited‐state structure of DPAC and its numerous analogues could be mimicked by model structures Mx‐My, demonstrating for the first time the the conformation change from bent‐to‐planar and hence a large range of energy‐gap tuning of polycyclic conjugated structures controlled by the steric hindrance.
Six (D)PAC: ortho‐Methyl effects are exploited to tune the steric hindrance between side‐chain N,N′‐diaryls and polycyclic dihydrodibenzoa,cphenazine, and in turn control the conformation and color of N,N′‐diphenyl‐dihydrodibenzoa,cphenazine (DPAC) and its ortho‐methyl derivatives. The results show that simple insertion of a small methyl group overcomes the energy barrier to planarization in the ground state.
By using the thiazolo5,4-dthiazole (TzTz) moiety as the core of a proton acceptor, compounds 2,2′-(thiazolo5,4-dthiazole-2,5-diyl)bis(4-tert-butylphenol) ( t -HTTH) and ...4-tert-butyl-2-(5-(5-tert-butyl-2-methoxyphenyl)thiazolo5,4-dthiazol-2-yl)phenol ( t -MTTH) have been strategically designed and synthesized. Upon photoexcitation, both t -HTTH and t -MTTH undergo a reversible type excited-state intramolecular proton transfer (ESIPT), the underlying mechanism of which has been verified by femtosecond early relaxation dynamics in various solvents. The pre-equilibrium in the excited state leads to both normal (∼440 nm) and proton-transfer tautomer (∼560 nm) emissions, for which the intensity ratio is dependent on both the molecular structure and the polarity of surrounding media. As a result, the emission can be widely tuned from blue to yellow via white-light luminescence. On the basis of t -MTTH, a white organic light emitting diode (WOLED) was successfully fabricated, which achieved external quantum efficiency (ηext) of 1.70% with Commission Internationale de L’Eclairage coordinates of (0.29, 0.33). More importantly, the electroluminescent spectra show superior color stability that is independent of luminance. The result demonstrates for the first time a credible WOLED based on a unimolecular ESIPT reaction, which may have far-reaching implications for practical application.
A tailored strategy is utilized to modify 5,10-dimethylphenazine (DMP) to donor–acceptor type N,N′-disubstituted-dihydrodibenzoa,cphenazines. The representative compounds DMAC (N,N′-dimethyl), DPAC ...(N,N′-diphenyl), and FlPAC (N-phenyl-N′-fluorenyl) reveal significant nonplanar distortions (i.e., a saddle shape) and remarkably large Stokes-shifted emission independent of the solvent polarity. For DPAC and FlPAC with higher steric hindrance on the N,N′-substituents, normal Stokes-shifted emission also appears, for which the peak wavelength reveals solvent-polarity dependence. These unique photophysical behaviors are rationalized by electronic configuration coupled conformation changes en route to the geometry planarization in the excited state. This proposed mechanism is different from the symmetry rule imposed to explain the anomalously long-wavelength emission for DMP and is firmly supported by polarity-, viscosity-, and temperature-dependent steady-state and nanosecond time-resolved spectroscopy. Together with femtosecond early dynamics and computational simulation of the reaction energy surfaces, the results lead us to establish a sequential, three-step kinetics. Upon electronic excitation of N,N′-disubstituted-dihydrodibenzoa,cphenazines, intramolecular charge-transfer takes place, followed by the combination of polarization stabilization and skeletal motion toward the planarization, i.e., elongation of the π-delocalization over the benzoa,cphenazines moiety. Along the planarization, DPAC and FlPAC encounter steric hindrance raised by the N,N′-disubstitutes, resulting in a local minimum state, i.e., the intermediate. The combination of initial charge-transfer state, intermediate, and the final planarization state renders the full spectrum of interest and significance in their anomalous photophysics. Depending on rigidity, the N,N′-disubstituted-dihydrodibenzoa,cphenazines exhibit multiple emissions, which can be widely tuned from red to deep blue and even to white light generation upon optimization of the surrounding media.
Green tea and its bioactive components, especially polyphenols, possess many health-promoting and disease-preventing benefits, especially anti-inflammatory, antioxidant, anticancer, and metabolic ...modulation effects with multi-target modes of action. However, the effect of tea polyphenols on immune function has not been well studied. Moreover, the underlying cellular and molecular mechanisms mediating immunoregulation are not well understood. This review summarizes the recent studies on the immune-potentiating effects and corresponding mechanisms of tea polyphenols, especially the main components of (–)-epigallocatechin-3-gallate (EGCG) and (–)-epicatechin-3-gallate (ECG). In addition, the benefits towards immune-related diseases, such as autoimmune diseases, cutaneous-related immune diseases, and obesity-related immune diseases, have been discussed.
Probiotics have been reported to ameliorate symptoms of type 2 diabetes mellitus (T2DM) in animal models and human studies. We previously demonstrated that oral administration of Lactobacillus ...reuteri ADR-3 reduced insulin resistance in high-fructose-fed (HFD) rats. In the present study, we first identified another L. reuteri strain, ADR-1, which displayed anti-diabetes activity that reduced the levels of serum HbA1c and cholesterol and that increased antioxidant proteins in HFD rats. We further performed a randomized, double-blinded, placebo-controlled trial with a total of 68 T2DM patients to examine the beneficial effects of oral consumption of L. reuteri strains ADR-1 and ADR-3 and to investigate the associated changes in intestinal flora using a quantitative PCR method to analyze 16 S rRNA in fecal specimens. Significant reductions in HbA1c and serum cholesterol were observed in participants in the live ADR-1 consumption group (n = 22) after 3 months of intake when compared with those in the placebo group (n = 22). Although there was no significant difference in the HbA1c serum level among participants who consumed heat-killed ADR-3 (n = 24), the systolic blood pressure and mean blood pressure were significantly decreased after 6 months of intake. There was no obvious change in serum inflammatory cytokines or antioxidant proteins in participants after intaking ADR-1 or ADR-3, except for a reduction in IL-1β in the ADR-3 consumption group after 6 months of intake. With the analysis of fecal microflora, we found that L. reuteri or Bifidobacterium spp. were significantly increased in the ADR-1 and ADR-3 consumption groups, respectively, after 6 months of intake. Interestingly, a significant reduction in HbA1c was observed in the ADR-1 and ADR-3 consumption participants who displayed at least an 8-fold increase in fecal L. reuteri. We also observed that there was a significantly positive correlation between Bifidobacterium spp. and Lactobacillus spp. in participants with increased levels of fecal L. reuteri. In the ADR-1 intake group, the fecal Lactobacillus spp. level displayed a positive correlation with Bifidobacterium spp. but was negatively correlated with Bacteroidetes. The total level of fecal L. reuteri in participants in the ADR-3 consumption group was positively correlated with Firmicutes. In conclusion, L. reuteri strains ADR-1 and ADR-3 have beneficial effects on T2DM patients, and the consumption of different strains of L. reuteri may influence changes in intestinal flora, which may lead to different outcomes after probiotic intake.
For deeper understanding of the coupling of electronic processes with conformational motions, we exploit a tailored strategy to harness the excited-state planarization of N,N′-disubstituted ...dihydrodibenzoa,cphenazines by halting the structural evolution via a macrocyclization process. In this new approach, 9,14-diphenyl-9,14-dihydrodibenzoa,cphenazine (DPAC) is used as a prototype, in which the para sites of 9,14-diphenyl are systematically enclosed by a dialkoxybenzene-alkyl-ester or -ether linkage with different chain lengths, imposing various degrees of constraint to impede the structural deformation. Accordingly, a series of DPAC-n (n = 1–8) derivatives were synthesized, in which n correlates with the alkyl length, such that the strength of the spatial constraint decreases as n increases. The structures of DPAC-1, DPAC-3, DPAC-4, and DPAC-8 were identified by the X-ray crystal analysis. As a result, despite nearly identical absorption spectra (onset ∼400 nm) for DPAC-1–8, drastic chain-length dependent emission is observed, spanning from blue (n = 1, 2, ∼400 nm) and blue-green (n = 3–5, 500–550 nm) to green-orange (n = 6) and red (n = 7, 8, ∼610 nm) in various regular solvents. Comprehensive spectroscopic and dynamic studies, together with a computational approach, rationalized the associated excited-state structure responding to emission origin. Severing the linkage for DPAC-5 via lipase treatment releases the structural freedom and hence results in drastic changes of emission from blue-green (490 nm) to red (625 nm), showing the brightening prospect of these chemically locked DPAC-n in both fundamental studies and applications.
Middle East Respiratory Syndrome coronavirus (MERS-CoV) is an emerging viral pathogen that causes severe morbidity and mortality. Up to date, there is no approved or licensed vaccine or antiviral ...medicines can be used to treat MERS-CoV-infected patients. Here, we analyzed the antiviral activities of resveratrol, a natural compound found in grape seeds and skin and in red wine, against MERS-CoV infection.
We performed MTT and neutral red uptake assays to assess the survival rates of MERS-infected Vero E6 cells. In addition, quantitative PCR, western blotting, and immunofluorescent assays determined the intracellular viral RNA and protein expression. For viral productivity, we utilized plaque assays to confirm the antiviral properties of resveratrol against MERS-CoV.
Resveratrol significantly inhibited MERS-CoV infection and prolonged cellular survival after virus infection. We also found that the expression of nucleocapsid (N) protein essential for MERS-CoV replication was decreased after resveratrol treatment. Furthermore, resveratrol down-regulated the apoptosis induced by MERS-CoV in vitro. By consecutive administration of resveratrol, we were able to reduce the concentration of resveratrol while achieving inhibitory effectiveness against MERS-CoV.
In this study, we first demonstrated that resveratrol is a potent anti-MERS agent in vitro. We perceive that resveratrol can be a potential antiviral agent against MERS-CoV infection in the near future.
Nanoporous carbons with high surface area are achieved through direct carbonization of a commercially available zeolitic imidazolate framework (ZIF-8) without any additional carbon sources. The ...resultant nanoporous carbons exhibit high electrochemical capacitances in an acidic aqueous electrolyte.
We propose a new concept exploiting thermally activated delayed fluorescence (TADF) molecules as photosensitizers, storage units and signal transducers to harness solar thermal energy. Molecular ...composites based on the TADF core phenoxazine-triphenyltriazine (PXZ-TRZ) anchored with norbornadiene (NBD) were synthesized, yielding compounds PZDN and PZTN with two and four NBD units, respectively. Upon visible-light excitation, energy transfer to the triplet state of NBD occurred, followed by NBD → quadricyclane (QC) conversion, which can be monitored by changes in steady-state or time-resolved spectra. The small S
-T
energy gap was found to be advantageous in optimizing the solar excitation wavelength. Upon tuning the molecule's triplet state energy lower than that of NBD (61 kcal/mol), as achieved by another composite PZQN, the efficiency of the NBD → QC conversion decreased drastically. Upon catalysis, the reverse QC → NBD reaction occurred at room temperature, converting the stored chemical energy back to heat with excellent reversibility.
A series of new amino (NH)-type hydrogen-bonding (H-bonding) compounds comprising 2-(2′-aminophenyl)benzothiazole and its extensive derivatives were designed and synthesized. Unlike in the hydroxyl ...(OH)-type H-bonding systems, one of the amino hydrogens can be replaced with electron-donating/withdrawing groups. This, together with a versatile capability for modifying the parent moiety, makes feasible the comprehensive spectroscopy and dynamics studies of amino-type excited-state intramolecular proton transfer (ESIPT), which was previously inaccessible in the hydroxyl-type ESIPT systems. Empirical correlations were observed among the hydrogen-bonding strength (the N–H bond distances and proton acidity), ESIPT kinetics, and thermodynamics, demonstrating a trend that the stronger N–H···N hydrogen bond leads to a faster ESIPT, as experimentally observed, and a more exergonic reaction thermodynamics. Accordingly, ESIPT reaction can be harnessed for the first time from a highly endergonic type (i.e., prohibition) toward equilibrium with a measurable ESIPT rate and then to the highly exergonic, ultrafast ESIPT reaction within the same series of amino-type intramolecular H-bond system.
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