NAC (NAM-ATAF1, 2-CUC2) family members play important roles in various environmental responses. Here, we cloned a full-length NAC gene (954 bp) from Solanum lycopersicum (SlNAC1). This gene belonged to ATAF subfamily which included ATAF1 and ATAF2 of Arabidopsis thaliana. SlNAC1 expression was induced by chilling stress (4°C), heat stress (40°C), high salinity, osmotic stress and mechanical wounding. SlNAC1 transcripts were enhanced after application of abscisic acid, methyl jasmonate, salicylic acid, gibberellin, ethylene, methyl viologen and hydrogen peroxide. The seedlings of transgenic plants overexpressing SlNAC1 grew more leaves but were shorter than wild-type (WT) plants. SlNAC1 overexpression increased the chilling tolerance of tomato plants by maintaining the higher maximal photochemical efficiency of photosystem II and oxygen-evolving activities. Compared with WT plants, transgenic plants showed higher superoxide dismutase (EC 1.15.1.1) and catalase (EC 1.11.1.6) activities, which reduced levels of H2 O2 and superoxide anion radicals and promoted lower ion leakage and malondialdehyde content. The expression level of SlCBF1 in transgenic plants was also higher than that in WT plants under both normal conditions and chilling stress; this increased expression may be the main factor influencing the high chilling tolerance of transgenic plants. The results suggest that SlNAC1 plays important roles in diversiform plant-stress responses and diverse signaling pathways.

Catechins are well-known to possess health-promoting functions. The interaction of the catechins with other components in tea could alter their absorption and efflux. This study investigated whether the absorption of catechins is affected by caffeine and amino acids using the Caco-2 monolayer cell model. We found that (−)-epigallocatechin gallate (EGCG), (−)-epicatechin gallate (ECG), and (−)-epicatechin (EC) were all actively effluxed. Co-transportation of EGCG, ECG, or EC with caffeine, theanine, serine, or glycine increased their apparent permeability coefficient [P app(AP−BL) ] value by 3.42−5.40-fold, 1.19−5.75-fold, and 1.55−8.01-fold, respectively. Meanwhile, their efflux ratio values were significantly decreased. Moreover, the expression of multi-drug resistance protein 2 (MRP2) after 3 h of incubation with either 50 μM EGCG or 50 μM EC was elevated by 1.58-and 2.98-fold, respectively, while 50 μM ECG had no significantly effects. In addition, the expression of Pglycoprotein (P-gp) after treatment with either 50 μM EGCG, 50 μM ECG, or 50 μM EC was enhanced by 1.53-, 1.63-, and 1.80-fold, respectively. The addition of either caffeine or any one of the three amino acids decreased the expression of both MRP2 and P-gp induced by EGCG, and the expression of P-gp induced by ECG or EC also decreased. In contrast, only glycine decreased the expression of MRP2 induced by EC. Taken together, our data indicated that caffeine and theanine, glycine, or serine in tea might increase the absorption of catechins by the selectively suppressed expression of the efflux transporters induced by catechins.

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The interaction mechanism between thyroxine-binding globulin (TBG) and three methoxylated polybrominated diphenyl ethers (MeO-PBDEs) was analyzed by steady-state fluorescence, ultraviolet-visible (UV-visible) spectroscopy, circular dichroism (CD), molecular docking and molecular dynamics simulation methods. The results of the molecular docking technique revealed that 2 0 -MeO-BDE-3, 5-MeO-BDE-47, and 3-MeO-BDE-100 combined with TBG at the active site. The steady-state fluorescence spectra displayed that MeO-PBDEs quenched the endogenous fluorescence of TBG through static quenching mechanism, and complex formation between MeO-PBDEs and TBG was further indicated by UV-vis spectroscopy. The thermodynamic quantities showed that the binding process is spontaneous, and the major forces responsible for the binding are hydrogen bonding and hydrophobic interactions, which are consistent with the results of molecular docking to a certain extent. The results of CD confirmed that the secondary structure of TBG was changed after combining with MeO-PBDEs. The dynamic simulation results illustrated that the protein structure is more compact and changes in the secondary structure of TBG after binding to MeO-PBDEs. Additionally, we also utilized the molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) method to analyze the binding free energy of TBG and MeO-PBDEs. The results suggest that van der Waals force plays an essential role in the combination.

In this study, we determined the binding characteristics of perfluoroalkyl sulfonates (PFSAs) to the adenosine A2A receptor (A2AR) using various spectroscopic methods and computer simulation technologies. UV‐absorption, fluorescence spectra, and three‐dimensional fluorescence spectra results revealed the changes in the micro‐environment of the secondary structure of A2AR. By comparing the fluorescence spectroscopy of A2AR in the absence and presence of PFSAs, we found that PFSAs induced the static fluorescence quenching of A2AR. The thermodynamic parameters ▵H and ▵S indicated that van der Waals forces and electrostatic interactions predominantly stabilized the pollutant‐protein system. A molecular dynamics (MD) simulation study of the A2AR and A2AR‐PFSAs complex shows that A2AR‐PFSAs are stable. This study describes the binding mechanism of PFSAs to A2AR, which is very helpful in improving our understanding of the effect of PFSAs on peripheral tissues and the central nervous system.