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Microbial cell-based biosensors, which mostly rely on stress-responsive operons, have been widely developed to monitor environmental pollutants. Biosensors are usually more convenient and inexpensive than traditional instrumental analyses of environmental pollutants. However, the targets of biosensors are restricted by the limited number of genetic operon systems available. In this study, we demonstrated a novel strategy to overcome this limitation by engineering an enhanced green fluorescent protein (eGFP). It has been reported that combining two fragments of split-eGFP can form a native structure. Thus, we engineered new biosensors by inserting metal-binding loops (MBLs) between β-strands 9 and 10 of the eGFP, which then undergoes conformational changes upon interaction between the MBLs and targets, thereby emitting fluorescence. The two designed MLBs based on our previous study were employed as linkers between two fragments of eGFP. As a result, an Escherichia coli biosensor exhibited a fluorescent signal only when interacting with cadmium ions, revealing the prospect of a new biosensor for cadmium detection. Although this study is a starting stage for further developing biosensors, we believe that the proposed strategy can serve as basis to develop new biosensors to target various environmental pollutants.

Thymic stromal lymphopoietin (TSLP) is a cytokine derived from epithelial cells and plays an essential role in the onset and activation of Th2-derived allergic inflammatory conditions, including atopic dermatitis. Despite their potential as drug targets, well-defined small molecules that effectively block TSLP expression are still lacking. A plant-derived secondary metabolite, aurone, was derivatized based on bioisosteric replacement to identify compounds that inhibit the promoter activity of TSLP. Thirteen (E)-2-benzylidene-1-indanones were designed and synthesized, and their structures were identified using NMR spectroscopy and mass spectrometry. Inhibition of the expression of TSLP triggered by interleukin-4 (IL-4) caused by (E)-2-benzylidene-1-indanones was measured using a TSLP gene promoter-reporter activity assay. Because compound 12, (E)-5-methoxy-2-(3-methoxybenzylidene)-2,3-dihydro-1H-inden-1-one, showed the best activity, further biological experiments, including RT-PCR analysis, quantitative real-time PCR, and inhibitory effects on IL-4-induced early growth response-1 (EGR-1) expression, EGR-1 DNA-binding activity, and IL-4-induced phosphorylation of the mitogen-activated protein kinase (MAPK) signaling cascade were performed. This study demonstrated that compound 12 acts on MAPK to block IL-4-triggered mRNA expression of TSLP via the MAPK-EGR-1 signaling pathway in HaCaT keratinocytes.

It is important to have tools to measure the bioavailability to assess the risks of pollutants because the bioavailability is defined as the portions of pollutants showing the biological effects on living organisms. This study described the construction of tunable Escherichia coli whole-cell bioreporter (WCB) using the promoter region of zinc-inducible operon and its application on contaminated soils. It was verified that this WCB system showed specific and sensitive responses to cadmium rather than zinc in the experimental conditions. It was inferred that Cd(II) associates stronger with ZntR, a regulatory protein of zinc-inducible operon, than other metal ions. Moreover, the expression of reporter genes, egfp and mcherry, were proportional to the concentration of cadmium, thereby being a quantitative sensor to monitor bioavailable cadmium. The capability to determine bioavailable cadmium was verified with Cd(II) amended LUFA soils, and then the applicability on environmental systems was investigated with field soils collected from smelter area in Korea before and after soil-washing. The total amount of cadmium was decreased after soil washing, while the bioavailability was increased. Consequently, it would be valuable to have tools to assess bioavailability and the effectiveness of soil remediation should be evaluated in the aspect of bioavailability as well as removal efficiency.

The spiro compound, 5,5′-dimethoxy-1,3-bis(3-(trifluoromethyl)phenyl)-3,3a-dihydro-1H-spiro[cyclopenta[a]indene-2,2′-indene]-1′,8(3′H,8aH)-dione (4), was synthesized and identified by NMR spectroscopy, mass spectrometry, and X-ray crystallography. Compound 4, C36H26F6O4, was crystallized in the triclinic space group P-1with the cell parameters a = 8.8669(5) Å, b = 10.5298(8) Å, c = 17.0135(11) Å, α = 91.396(2)°, β = 90.490(2)°, γ = 109.235°, V = 1499.14(17) Å3, Z = 2. In an asymmetric unit, two molecules are packed by short contacts to form an inversion dimer. The molecules are linked into chains along the a- and b-axis directions by additional short contacts in the crystal. Compound 4 was synthesized by the dimerization of (E)-5-methoxy-2-(3-(trifluoromethyl)benzylidene)-2,3-dihydro-1H-inden-1-one (3). (E)-5-Methoxy-2-(3-methoxybenzylidene)-2,3-dihydro-1H-inden-1-one (5), one of the analogs of compound 3, was compared with compound 4 based on in vitro experiments, DFT calculations, and an in silico docking study. The HOMO/LUMO energy difference and binding energy difference between the two compounds are consistent with the results obtained from an in vitro assay where 4 showed a better effect than 5. To evaluate the biological activity of 4, we examined its inhibitory effects on Early Growth Respone-1 (EGR-1)-regulated gene expression in HaCaT keratinocytes. Treatment of cells with 4 reduced interleukin-4 (IL-4)-induced thymic stromal lymphopoietin (TSLP) mRNA levels, as revealed by reverse transcription-polymerase chain reaction and quantitative real-time PCR. Furthermore, the electrophoretic mobility shift assay demonstrated that 4 inhibited IL-4-induced DNA binding of EGR-1 to the promoter region of the TSLP gene.

Resveratrol is a typical plant phenolic compound whose derivatives are synthesized through hydroxylation, O -methylation, prenylation, and oligomerization. Resveratrol and its derivatives exhibit anti-neurodegenerative, anti-rheumatoid, and anti-inflammatory effects. Owing to the diverse biological activities of these compounds and their importance in human health, this study attempted to synthesize five resveratrol derivatives (isorhapontigenin, pterostilbene, 4-methoxyresveratrol, piceatannol, and rhapontigenin) using Escherichia coli . Two-culture system was used to improve the final yield of resveratrol derivatives. Resveratrol was synthesized in the first E. coli cell that harbored genes for resveratrol biosynthesis including TAL (tyrosine ammonia lyase), 4CL (4-coumaroyl CoA ligase), STS (stilbene synthase) and genes for tyrosine biosynthesis such as aroG (deoxyphosphoheptonate aldolase) and tyrA (prephenate dehydrogenase). Thereafter, culture filtrate from the first cell was used for the modification reaction carried out using the second E. coli harboring hydroxylase and/or O -methyltransferase. Approximately, 89.8 mg/L of resveratrol was synthesized and using the same, five derivatives were prepared with a conversion rate of 88.2% to 22.9%. Using these synthesized resveratrol derivatives, we evaluated their anti-inflammatory activity. 4-Methoxyresveratrol, pterostilbene and isorhapontigenin showed the anti-inflammatory effects without any toxicity. In addition, pterostilbene exhibited the enhanced anti-inflammatory effects for macrophages compared to resveratrol.

Plant-derived phenolic compounds, such as hydroxytyrosol and hydroxysalidroside, have a beneficial impact on human health owing to their antioxidant activity. In this study, we used Escherichia coli to synthesize hydroxytyrosol. Tyrosine decarboxylase from Papaver somniferum , tyrosine oxidase from Micrococcus luteus , and 4-hydroxyphenylacetate 3-monooxygenase from E. coli were transformed into the bacterial cell. The resulting transformant successfully synthesized hydroxytyrosol. Furthermore, we used the engineered E. coli strains to synthesize ~ 268.3 mg/L hydroxytyrosol. Three uridine diphosphate-dependent glycosyltransferases (UGTs), which were previously shown to convert tyrosol into salidroside, were tested to synthesize hydroxysalidroside, and one of UGTs was used to synthesize hydroxysalidroside from hydroxytyrosol. Finally, E. coli harboring this UGT converted approximately 50% of hydroxytyrosol into hydroxysalidroside.

Significant efforts have been devoted to the development of nanoparticular delivering systems targeting tumors. However, clinical application of nanoparticles is hampered by insufficient size homogeneity, difficulties in reproducible synthesis and manufacturing, frequent high uptake in the liver, systemic toxicity of the carriers (particularly for inorganic nanoparticles), and insufficient selectivity for tumor cells. We have found that properly modified synthetic analogs of transmembrane domains of membrane proteins can self-assemble into remarkably uniform spherical nanoparticles with innate biological activity. Self-assembly is driven by a structural transition of the peptide that adopts predominantly a beta-hairpin conformation in aqueous solutions, but folds into an alpha-helix upon spontaneous fusion of the nanoparticles with cell membrane. A 24-amino acid peptide corresponding to the second transmembrane helix of the CXCR4 forms self-assembled particles that inhibit CXCR4 function in vitro and hamper CXCR4-dependent tumor metastasis in vivo. Furthermore, such nanoparticles can encapsulate hydrophobic drugs, thus providing a delivery system with the potential for dual biological activity.

Various flavonoid O -diglycosides are found in nature but the biological activities of only a few compounds have been explored due to difficulty in obtaining samples. In order to circumvent the need for extraction and purification of the natural compounds from plants, we used engineered Escherichia coli strain that harbors two uridine diphosphate-dependent glycosyltransferases (UGTs; BcGT1 and CaUGT ) and two nucleotide sugar biosynthetic genes ( pgm and galU ). Using this strain, we synthesized quercetin 3- O -gentiobioside. After optimization of induction temperature, cell density, and reaction temperature, approximately 46.2 mg/L quercetin 3- O -gentiobioside was synthesized from quercetin with 49 % conversion efficiency.

Members of the aurora kinase family are Ser/Thr kinases involved in regulating mitosis. Multiple promising clinical trials to target aurora kinases are in development. To discover flavones showing growth inhibitory effects on cancer cells, 36 flavone derivatives were prepared, and their cytotoxicity was measured using a long-term clonogenic survival assay. Their half-maximal growth inhibitory effects against HCT116 human colon cancer cells were observed at the sub-micromolar level. Pharmacophores were derived based on three-dimensional quantitative structure–activity calculations. Because plant-derived flavones inhibit aurora kinase B, we selected 5-methoxy-2-(2-methoxynaphthalen-1-yl)-4H-chromen-4-one (derivative 31), which showed the best half-maximal cell growth inhibitory effect, and tested whether it can inhibit aurora kinases in HCT116 colon cancer cells. We found that derivative 31 inhibited the phosphorylation of aurora kinases A, aurora kinases B and aurora kinases C, suggesting that derivative 31 is a potential pan-aurora kinase inhibitor. The results of our analysis of the binding modes between derivative 31 and aurora A and aurora B kinases using in-silico docking were consistent with the pharmacophores proposed in this study.