Activation and Characterization of Cryptic Gene Cluster: Two Series of Aromatic Polyketides Biosynthesized by Divergent Pathways.

One biosynthetic gene cluster (BGC) usually governs the biosynthesis of a series of compounds exhibiting either the same or similar molecular scaffolds. Reported here is a multiplex activation strategy to awaken a cryptic BGC associated with tetracycline polyketides, resulting in the discovery of compounds having different core structures. By constitutively expressing a positive regulator gene in tandem mode, a single BGC directed the biosynthesis of eight aromatic polyketides with two types of frameworks, two pentacyclic isomers and six glycosylated tetracyclines. The proposed biosynthetic pathway, based on systematic gene inactivation and identification of intermediates, employs two sets of tailoring enzymes with a branching point from the same intermediate. These findings not only provide new insights into the role of tailoring enzymes in the diversification of polyketides, but also highlight a reliable strategy for genome mining of natural products.

Temperature-Dependent Separation of CO2 from Light Hydrocarbons in a Porous Self-Assembly of Vertexes Sharing Octahedra.

Design of flexible porous materials where the diffusion of guest molecules is regulated by the dynamics of contracted pore aperture is challenging. Here, a flexible porous self-assembly consisting of 1D channels with dynamic bottleneck gates is reported. The dynamic pendant naphthimidazolylmethyl moieties at the channel necks provide kinetic gate function, that enables unusual adsorption for light hydrocarbons. The adsorption for CO2 is mainly dominated by thermodynamics with the uptakes decreasing with increasing temperature, whereas the adsorptions for larger hydrocarbons are controlled by both thermodynamics and kinetics resulting in an uptake maximum at a temperature threshold. Such an unusual adsorption enables temperature-dependent separation of CO2 from the corresponding hydrocarbons.

Leptin attenuates lipopolysaccharide or oleic acid-induced acute lung injury in mice.

Leptin is reported to be involved in acute lung injury (ALI). However, the role and underlying mechanisms of leptin in ALI remain unclear. The aim of this study was to determine whether leptin deficiency promoted the development of ALI. LPS or oleic acid (OA) were administered to wild-type and leptin deficient (ob/ob) mice to induce ALI. Leptin level, survival rate, and lung injury were examined. Results showed that leptin levels were predominantly increased in the lung, but also in the heart, liver, kidney, and adipose tissue after LPS adminiatration. Compared with wild-type mice, LPS- or OA-induced lung injury was worse and the survival rate was lower in ob/ob mice. Moreover, leptin deficiency promoted the release of proinflammatory cytokines. Exogenous administration of leptin reduced lethality in ob/ob mice and ameliorated lung injury partly through inhibiting the activation of NF-κB, p38, and ERK pathways. These results indicated that leptin deficiency contributed to the development of lung injury by enhancing inflammatory response, and a high level of leptin improved survival and protected against ALI.

Fabrication of Lanthanide-Functionalized Hydrogen-Bonded Organic Framework Films for Ratiometric Temperature Sensing by Electrophoretic Deposition.

Developing a noncontact ratiometric luminescent temperature sensor with high sensitivity, widely available emission range, and reliable performance is a challenge in materials science. Herein, we demonstrated that this goal can be achieved by fabricating a lanthanide-functionalized hydrogen-bonded organic framework film (named the Eu@HOF-TCBP film). The unbonded carboxylic groups that existed in the structure not only enable lanthanide ions to bind with the framework for bringing dual emission but also allow for preparing a hydrogen-bonded organic framework (HOF) film through the facile electrophoretic deposition. The obtained film exhibits ratiometric temperature sensing performance in the range of 297-377 K with a maximum relative sensitivity of 5.787% K-1 and shows repeated use without sensitivity loss. Moreover, the material can be easily recycled and refabricated with consistent performance, demonstrating its unique merits of easy recyclability and regeneration as an HOF material. We believe that the reported strategies for preparing a dual-emitting HOF and fabricating a thin film will open a window for HOF applications.

Molecular cloning of a novel cDNA from Mus muscular BALB/c mice encoding glycosyl hydrolase family 1: a homolog of human lactase-phlorizin hydrolase.

OBJECTIVE: To study the mechanism of lactose intolerance (LI) by cloning the mouse lactase cDNA and recombining a vector. METHODS Total murine RNA was isolated from the small intestine of a 4-week-old BALB/c mouse (d). Gene-specific primers were designed and synthesized according to the cDNA sequences of lactase-phlorizin hydrolase (LPH) in human, rat, and rabbit. A coding sequence (CDS) fragment was obtained using RT-PCR, and inserted into a clone vector pNEB-193, then the cDNA was sequenced and analyzed using bioinformatics. RESULTS: The cDNA from the BALB/c mouse with 912 bp encoding 303 amino acid residues. Analysis of the deduced amino acid sequence using bioinformatics revealed that this cDNA shared extensive sequence homology with human LPH containing a conserved glycosyl hydrolase family 1 motif important for regulating lactase intolerance. CONCLUSION: BALB/c mouse LPH cDNA (GenBank accession No: AY751548) provides a necessary foundation for study of the biological function and regulatory mechanism of the lactose intolerance in mice.

[Expression of protein 4.1 family in melanoma cell lines and its effect on cell proliferation].

OBJECTIVE: To detect the expression of protein 4.1 family members in mouse melanoma cell lines and evaluate their effect on cell proliferation. METHODS: PCR and Western blot were used to detected to the expression of protein 4.1 family members (4.1R, 4.1B, 4.1G, and 4.1N) at the mRNA and protein levels in B16 and B16-F10 cell lines. The expression plasmid vector pEGFP-N1-EPB41L3 carrying 4.1B gene sequence amplified from genomic RNA of mouse embryo fibroblasts was constructed and transiently transfected into mouse melanoma cells. The change in cell proliferation was assessed using MTT assay. RESULTS: The mRNA and protein expressions of all the protein 4.1 family members, with the exception of 4.1B, were detected in both B16 and B16-F10 cells. Transfection of cells with the eukaryotic expression vector pEGFP-N1-EPB41L3 markedly inhibited cell proliferation as compared with the non-transfected cells. CONCLUSION: The eukaryotic expression vector carrying EPB41L3 sequence is capable of inhibiting the proliferation of mouse melanoma B16 and B16-F10 cells.

[A simulation study of electrical impedance scan-imaging based on a phantom].

OBJECTIVE: To testify the feasibility of electrical impedance scanning (EIS) imaging and to classify the factors influencing EIS imaging at the early stage of electrical impedance scanning breast imaging study. METHOD: Based on the EIS experiment workplace, a phantom to simulate the distribution of breast tissue was designed. Using NaCl solution and agar block with different conductance, three kinds of electric fields disturbances were simulated. RESULT: Different electric fields disturbance induced by different conductance distributions bring different imaging effects. CONCLUSION: The imaging based on the theory of EIS is feasible. Initiative factors influencing EIS imaging are confirmed.

Electrical impedance scanning in breast tumor imaging: correlation with the growth pattern of lesion.

BACKGROUND: This study researched the electric impedance properties of breast tissue and demonstrated the different characteristic of electrical impedance scanning (EIS) images. METHODS: The impedance character of 40 malignant tumors, 34 benign tumors and some normal breast tissue from 69 patients undergoing breast surgery was examined by EIS in vivo measurement and mammography screening, with a series of frequencies set between 100 Hz - 100 kHz in the ex vivo spectroscopy measurement. RESULTS: Of the 39 patients with 40 malignant tumors, 24 showed bright spots, 11 showed dark areas in EIS and 5 showed no specific image. Of the 30 patients with 34 benign tumors there were almost no specific abnormality shown in the EIS results. Primary ex vivo spectroscopy experiments showed that the resistivity of various breast tissue take the following pattern: adipose tissue > cancerous tissue > mammary gland and benign tumor tissue. CONCLUSIONS: There are significant differences in the electrical impedance properties between cancerous tissue and healthy tissue. The impedivity of benign tumor is lower, and is at the same level with that of the mammary glandular tissue. The distinct growth pattern of breast lesions determined the different electrical impedance characteristics in the EIS results.