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Urease is a metalloenzyme that catalyzes the hydrolysis of urea into ammonia and carbon dioxide, which has a negative impact on human health and agriculture. In this study, the inactivation of jack bean urease by nitidine chloride (NC) was investigated to elucidate the inhibitory effect, kinetics, and underlying mechanism of action. The results showed that NC acted as a concentration- and time-dependent inhibitor with an IC50 value of 33.2 ± 4.8 μM and exhibited a similar inhibitory effect to acetohydroxamic acid (IC50 = 31.7 ± 5.8 μM). Further kinetic analysis demonstrated that NC was a slow-binding and non-competitive inhibitor for urease. Thiol-blocking reagents (dithiothreitol, glutathione, and l-cysteine) significantly retarded urease inactivation, while Ni2+ competitive inhibitors (boric acid and sodium fluoride) synergetically suppressed urease with NC, suggesting that the active site sulfhydryl groups were possibly obligatory for NC blocking urease. Molecular docking simulation further argued its inhibition mechanism. Additionally, NC-induced deactivation of urease was verified to be reversible since the inactivated enzyme could be reactivated by glutathione. Taking together, NC was a non-competitive inhibitor targeting the thiol group at the active site of urease with characteristics of concentration dependence, reversibility, and slow binding, serving as a promising novel urease suppressant.

Urease is a metalloenzyme that catalyzes the hydrolysis of urea into ammonia and carbon dioxide, which has a negative impact on human health and agriculture. In this study, the inactivation of jack bean urease by nitidine chloride (NC) was investigated to elucidate the inhibitory effect, kinetics, and underlying mechanism of action. The results showed that NC acted as a concentration- and time-dependent inhibitor with an IC

The present study aimed to explore the neural correlates underlying the effects of idea evaluation on idea generation in creative thinking. Participants were required to generate original uses of conventional objects (alternative uses task) during EEG recording. A reflection task (mentally evaluating the generated ideas) or a distraction task (object characteristics task) was inserted into the course of idea generation. Behavioral results revealed that participants generated ideas with higher originality after evaluating the generated ideas than after performing the distraction task. The EEG results revealed that idea evaluation was accompanied with upper alpha (10-13 Hz) synchronization, most prominent at frontal cortical sites. Moreover, upper alpha activity in frontal cortices during idea generation was enhanced after idea evaluation. These findings indicate that idea evaluation may elicit a state of heightened internal attention or top-down activity that facilitates efficient retrieval and integration of internal memory representations.

Previous studies have uncovered various influencing factors of the incubation effect in creative problem solving. Often, tests of divergent thinking (DT) are used as estimates of the potential for creative problem solving. The impact of emotional state during the incubation interval on subsequent creative performance has not yet been investigated. A within-subject design was used in this study. Participants (N 44) were asked to solve the instances problems (i.e., a verbal DT task) in four conditions (positive, neutral, negative incubation conditions, and a continuous working condition). During the incubation intervals, participants watched a series of emotion-appropriate videos to induce corresponding emotions. The results showed that participants’ originality scores were higher after an incubation interval (regardless of the emotions induced) than when continuously working. Originality scores were the highest when positive emotion was induced during the incubation interval. These findings demonstrated that emotional state during the incubation interval influences the incubation effect. The findings are interpreted in the context of the unconscious work theory of incubation. Limitations and future directions are explored.

Previous studies revealed inconsistent findings about the effects of cognitively low or high demanding interpolated tasks during incubation period on post-incubation creative performance. To explain this contradiction, two intervention tasks were administered (Reflecting on the generated ideas [RF] and the Word puzzle task [WP]), which are supposed to elicit remote associative processes but with varying levels of cognitive demands, along with two verbal control tasks (phonemic fluency task and object characteristics task). A delayed-incubation paradigm was used to assess whether performance on verbal creative problem solving (Alternative Uses Task, AUT) could be stimulated by the applied intervention tasks. The results showed that only RF and WP tasks, but not the control tasks, were associated with significant incubation effects. The findings suggest that the interpolated tasks that were assumed to elicit remote associative processes can unfold beneficial effects on verbal creative problem solving, regar...

A method for determination of vitamin B1 has been developed that is based on the enhancement effect of vitamin B1 on the luminescence of water-soluble CdTe nanorods modified with thioglycolic acid and cysteine. The effect of variables including the size of the nanorods on the enhancement of luminescence have been investigated. A preliminary mechanistic study showed that the passivating action of vitamin B1 on the surface of the CdTe nanorods is likely to be responsible for the enhancement. Interferences by shortwave fluorescence are effectively eliminated because measurements are performed in the near-infrared. Due to the near-infrared measurement character, the fluorescence interference of vitamin B2 can be effectively eliminated. Under the optimum conditions, the extent of luminescence enhancement is proportional to the concentration of vitamin B1 in the range from 0.1 to 3.0 μmol L−1 and the detection limit is 0.03 μmol L−1. The relative standard deviation for 2.0 μmol L−1 vitamin B1 is 1.3% (n = 6). The method is highly sensitive and selective, avoids the sample treatment needed in other procedures, and can be applied to the determination of vitamin B1 in real samples with satisfactory results.

CdS quantum dots (QD) were capped with SiO2 via a microemulsion method for reducing the toxicity and imparting the biocompatibility of the CdS QD. The resulting CdS/SiO2 core/shell nanoparticles (NP) showed an improved water-solubility and stability even in pH 4.0 acidic medium. Their fluorescence could be effectively enhanced in the presence of bovine serum albumin (BSA), due to the passivation effect of BSA on the surface of the NP. Furthermore, the concentration dependence of the fluorescence intensity obeys the Langmuir-type binding isotherm. Thus a novel fluorescence enhancement method for the determination of BSA has been developed using the less-toxic CdS/SiO2 core/shell NP as probes. Under optimal conditions, the linear range of calibration curve is 0.6–30 µg·mL−1, and the detection limit is 0.18 µg·mL−1. Compared with the water-soluble CdS NP without SiO2 shell, the CdS/SiO2 core/shell NP exhibited slightly lower fluorescence response to BSA as well as other coexisting substances, such as heavy and transition metals, due to the inhibition of SiO2 shell. The proposed method was applied to the quantification of BSA in synthetic and serum samples with satisfactory results.

Glutathione-capped CdTe quantum dots (GSH-CdTe QDs) were synthesized in aqueous medium. Their interactions with proteins, especially three heme-containing proteins, were investigated over a broad pH range. At 6.0 8.0, only cytochrome c quenched the fluorescence of the GSH-CdTe QDs, and no significant fluorescence changes were observed for hemoglobin or other proteins. Based on the distinct fluorescence response, a novel method has been developed for the selective determination of cytochrome c using GSH-CdTe QDs as the fluorescence probe at pH 9.0. Under optimum conditions, the linear range of the calibration curve is from 3.2 × 10−8 to 2.4 × 10−6 mol L−1 and the detection limit is 3.0 × 10−9 mol L−1. The method has been applied to the determination of cytochrome c in three synthetic and real samples, and satisfactory results were obtained with QDs through selecting the proper pH value.

A novel method for the determination of berberine has been developed based on quenching of the fluorescence of thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) by berberine in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of berberine between 2.5x10(-8) and 8.0x10(-6)mol L(-1) with a detection limit of 6.0x10(-9)mol L(-1). The method has been applied to the determination of berberine in real samples, and satisfactory results were obtained. The mechanism of the proposed reaction was also discussed.