3-Nitroindoles Serving as N-Centered Nucleophiles for Aza-1,6-Michael Addition to para-Quinone Methides.

An unprecedented N-alkylation of 3-nitroindoles with para-quinone methides was developed for the first time. Using potassium carbonate as the base, a wide range of structurally diverse N-diarylmethylindole derivatives were obtained with moderated to good yields via the protection group migration/aza-1,6-Michael addition sequences. The reaction process was also demonstrated by control experiments. Different from the previous advances where 3-nitrodoles served as electrophiles trapping by various nucleophiles, the reaction herein is featured that 3-nitrodoles is defined with latent N-centered nucleophiles to react with ortho-hydrophenyl p-QMs for construction of various N-diarylmethylindoles.

Combined Use of Texture Features and Morphological Classification Based on Dynamic Contrast-enhanced MR Imaging: Differentiating Benign and Malignant Breast Masses with High Negative Predictive Value.

PURPOSE: We evaluated the diagnostic performance of the texture features of dynamic contrast-enhanced (DCE) MRI for breast cancer diagnosis in which the discriminator was optimized, so that the specificity was maximized via the restriction of the negative predictive value (NPV) to greater than 98%. METHODS: Histologically proven benign and malignant mass lesions of DCE MRI were enrolled retrospectively. Training and testing sets consist of 166 masses (49 benign, 117 malignant) and 50 masses (15 benign, 35 malignant), respectively. Lesions were classified via MRI review by a radiologist into 4 shape types: smooth (S-type, 34 masses in training set and 8 masses in testing set), irregular without rim-enhancement (I-type, 60 in training and 14 in testing), irregular with rim-enhancement (R-type, 56 in training and 22 in testing), and spicula (16 in training and 6 in testing). Spicula were immediately classified as malignant. For the remaining masses, 298 texture features were calculated using a parametric map of DCE MRI in 3D mass regions. Masses were classified into malignant or benign using two thresholds on a feature pair. On the training set, several feature pairs and their thresholds were selected and optimized for each mass shape type to maximize specificity with the restriction of NPV > 98%. NPV and specificity were computed using the testing set by comparison with histopathologic results and averaged on the selected feature pairs. RESULTS: In the training set, 27, 12, and 15 texture feature pairs are selected for S-type, I-type, and R-type masses, respectively, and thresholds are determined. In the testing set, average NPV and specificity using the selected texture features were 99.0% and 45.2%, respectively, compared to the NPV (85.7%) and specificity (40.0%) in visually assessed MRI category-based diagnosis. CONCLUSION: We, therefore, suggest that the NPV of our texture-based features method described performs similarly to or greater than the NPV of the MRI category-based diagnosis.

Carbon Isotope Fractionation Characteristics of Normally Pressured Shale Gas from the Southeastern Margin of the Sichuan Basin; Insights into Shale Gas Storage Mechanisms.

Since the development of shale gas in the Wufeng-Longmaxi Formation in the Sichuan Basin, China's shale gas production and reserves have increased rapidly. The southeastern margin of the Sichuan Basin is located in a normally pressured transition zone, where single well gas production varies greatly under complex geological structures. In order to reveal the shale gas enrichment mechanism and favorable shale gas regions, shale gas samples from production wells were collected from different structures, with the formation pressure coefficient ranging between 0.98 and 1.35. The gas components and carbon isotope characteristics of normally pressured shale gas were investigated. The carbon isotope characteristics of the Wufeng-Longmaxi shale gas from the basin scale was mainly controlled using thermal maturity; as the thermal maturity increased, heavier carbon isotopes were found, in addition to drier shale gas. For normally pressured shale gas, the composition of δ13C1 and δ13C2 becomes heavier, and the dryness coefficient decreases with the decreasing pressure coefficient; this is not consistent with the results from thermal evolution. By comparing possible influencing factors, it is evident that the change in geological structure destroys the original shale gas reservoir, which leads to the escape of some gases, and it may be the main factor that contributes to the gas geochemical characteristics of the normally pressured shale gas. Compared with the geological parameters of the shale samples, such as mineral composition, organic abundance, organic pore distribution, and gas content, the carbon isotope characteristics of normally pressured shale gas show a higher efficiency, thus indicating favorable sweet spot evaluations for shale gas in the studied areas.

Cloning and expression of the flavin reductase LuxG from Photobacterium leiognathi YL and its improvement for NADH detection.

In the present study, we aimed to purify and characterize LuxG obtained from Photobacterium leiognathi YL and examine its improvement for NADH detection. To this end, we cloned and expressed the putative luxG gene of P. leiognathi YL in the Escherichia coli BL21 strain. The product of luxG is a flavin reductase that consists of 206 amino acids, corresponding to a subunit molecular mass of ∼26 kDa. Phylogenetic analysis demonstrated that P. leiognathi YL LuxG has a rather distant evolutionary relationship with Frase I of Aliivibrio fischeri and Frp of Vibrio harveyi, but a close evolutionary relationship with Fre from Escherichia coli, which are all enzymes related to oxido-reductase. Further comparison shows that the changes in the functionally conserved sites may contribute to the functional divergence of LuxG and Fre. LuxG could supply reduced flavin mononucleotide (FMN) for bacterial luminescence by catalyzing the oxidation of nicotinamide adenine dinucleotide hydrogen (NADH). Based on this, a coupled pure enzyme bioluminescent system was established and used for NADH detection. The NADH samples with concentrations of 0.1-1 nM were used to validate the linear relationship, and it was found that the logarithmic deviations were less than 3%, which showed more sensitive and stable results than the NADH detection by recombinant E. coli including the exogenously expressed luciferase and intrinsic Fre. Investigation of P. leiognathi YL LuxG would provide a basic understanding of its evolution, and structural and functional properties, which might contribute to the development of a NADH detection kit in the future.

Expression of genes encoding the luciferase from Photobacterium leiognathi in Escherichia coli Rosetta (DE3) and its application in NADH detection.

Cloning of genes encoding the luciferase from Photobacterium leiognathi YL in Escherichia coli Rosetta (DE3) was performed successfully and the expressed forms of lux AB were purified to homogeneity. Experimental measurements revealed that luciferase from Photobacterium leiognathi YL has good thermal stability and a high residual activity at extreme pH values, which are extremely important for its various ecological, industrial and medical applications. Furthermore, we made a first attempt for quantitative detection of NADH by recombinant E. coli Rosetta (DE3) coupled enzyme system. A good linear relationship between luminescence intensity and NADH with low (1-12 nmol/L) and high (10-500 nmol/L) concentration was observed, whose standard curve was y = 772.97× + 4041.1, R2  = 0.9884 and y = 1710× + 4.99 × 105 , R2  = 0.9727, respectively. Our results demonstrate a high sensitivity of recombinant E. coli coupled enzyme system to NADH on the basis of high soluble expression of recombinant luciferase and continuous and stable expression of some NAD(P)H-dependent flavin mononucleotide (FMN) reductases.