Acremolin,a new 1H-azirine metabolite from the marine-derived fungus Acremonium strictum

Acremolin (1), a novel modified base, was isolated from the culture broth of the marine fungus Acremonium strictum. Based on combined spectroscopic analyses, the structure of this compound was that of a methyl guanine base containing an isoprene unit. In addition, the presence of a 1H-azirine moiety is unprecedented among natural products. This compound exhibited weak cytotoxicity against an A549 cell line.     

Bithiazole metabolites from the myxobacterium Myxococcus fulvus

Two new bithiazole metabolites (3, 4) along with the previously reported compounds (1, 2) were isolated from the culture broth of the gliding bacterium Myxococcus fulvus collected from a Korean soil. The structures of these compounds were determined to be analogous to myxothiazole A on the basis of combined spectroscopic analyses. The new compounds exhibited significant cytotoxicity and moderate antifungal activity against the mouse fibloblast cell-line L929 and Candida albicans, respectively. These data were consistent with the previous finding that the bioactivity of myxothiazoles was highly dependent on the presence of terminal methoxy enol functionality.     

Discovery of Terminal Oxazole-Bearing Natural Products by a Targeted Metabologenomic Approach

A targeted metabologenomic method was developed to selectively discover terminal oxazole-bearing natural products from bacteria. For this, genes encoding oxazole cyclase, a key enzyme in terminal oxazole biosynthesis, were chosen as the genomic signature to screen bacterial strains that may produce oxazole-bearing compounds. Sixteen strains were identified from the screening of a bacterial DNA library (1,000 strains) using oxazole cyclase gene-targeting polymerase chain reaction (PCR) primers. The PCR amplicon sequences were subjected to phylogenetic analysis and classified into nine clades. ¹H−¹³C coupled-HSQC NMR spectra obtained from the culture extracts of the hit strains enabled the unequivocal detection of the target compounds, including five new oxazole compounds, based on the unique ¹J_CH values and chemical shifts of oxazole: lenzioxazole ( 1 ) possessing an unprecedented cyclopentane, permafroxazole ( 2 ) bearing a tetraene conjugated with carboxylic acid, tenebriazine ( 3 ) incorporating two modified amino acids, and methyl-oxazolomycins A and B ( 4 and 5 ). Tenebriazine displayed inhibitory activity against pathogenic fungi, whereas methyl-oxazolomycins A and B ( 4 and 5 ) selectively showed anti-proliferative activity against estrogen receptor-positive breast cancer cells. This metabologenomic method enables the logical and efficient discovery of new microbial natural products with a target structural motif without the need for isotopic labeling.     

Chalcogen-based thin film transistor using CuInSe2 photo-active layer

We propose chalcogen-based photo-thin film transistor (P-TFT) using CuInSe₂ (CIS) homo-junction. By using a tri-layer process, we fabricated n- and p-type CIS films. Optical and electrical properties of the fabricated CIS films are measured to be suitable for homo-junction. For the fabrication of a P-TFT, n-type CIS generating higher photo current was used for a channel layer whereas p-type CIS with higher carrier density was used for source and drain. The fabricated transistor exhibited typical transistor operation of p-channel enhancement mode and current increase with light.     

Photodiode-Based Chua＇s Circuit with Light Controllability

We present a photodiode-based Chua＇s chaotic circuit that is controllable by light. The proposed circuit consists of an inductor, two passive capacitors, a photodiode-based variable resistor, and a positive feedback trans- conductor with negative nonlinearity. The chaotic dynamics of the circuit were verified by using the simulation program with integrated circuit emphasis analysis using the 0.35 #m complementary metal-oxide-semiconductor process parameters. The gain results （such as the time waveform~ frequency analysis, three-dimensional attractor, bifurcation and Lyapunov exponents diagrams） confirm that the chaotic behavior of the circuit could be controlled by light intensity via the photodiode-based variable resistor.     

A QUANTITATIVE EVALUATION OF ELASTIC WAVE IN SOLID BY STROBOSCOPIC PHOTOELASTICITY

We have developed a method for visually measuring and evaluating stresses emitted from an ultrasonic probe into a model solid similar to the actual material, by using image-processing techniques and stroboscopic photoelasticity. The visualization of wave stress (sound pressure) distribution can be achieved by synthesizing two photoelastic pictures, in which the directions of the principal axes of linear polariscopes are different by 45 degrees. The sound pressure field generated by commercial ultrasonic probes was measured by using the proposed method.     

Non-associative algebras containing the matrix ring

The Lie admissible non-associative algebra is defined in the papers [Seul Hee Choi, Ki-Bong Nam, Derivations of a restricted Weyl type algebra I, Rocky Mountain J. Math. 37 (6) (2007) 1813–1830; Seul Hee Choi, Ki-Bong Nam, Weyl type non-associative algebra using additive groups I, Algebra Colloq. 14 (3) (2007) 479–488; Ki-Bong Nam, On Some Non-associative Algebras using Additive Groups, Southeast Asian Bull. Math., vol. 27, Springer-Verlag, 2003, 493–500]. We define in this work the algebra which generalizes the previous one and is not Lie admissible. We prove that the antisymmetrized Lie algebra is simple and contains the simple Lie algebra . We also prove that the matrix ring is embedded in .     

Discovery and Biosynthesis of Cihunamides,Macrocyclic Antibacterial RiPPs with a Unique C−N Linkage Formed by CYP450 Catalysis

Cihunamides A–D ( 1 – 4 ), novel antibacterial RiPPs, were isolated from volcanic-island-derived Streptomyces sp. The structures of 1 – 4 were elucidated by ¹H, ¹³C, and ¹⁵N NMR, MS, and chemical derivatization; they contain a tetrapeptide core composed of WNIW, cyclized by a unique C−N linkage between two Trp units. Genome mining of the producer strain revealed two biosynthetic genes encoding a cytochrome P450 enzyme and a precursor peptide. Heterologous co-expression of the core genes demonstrated the biosynthesis of cihunamides through P450-mediated oxidative Trp-Trp cross-linking. Further bioinformatic analysis uncovered 252 homologous gene clusters, including that of tryptorubins, which possess a distinct Trp-Trp linkage. Cihunamides do not display the non-canonical atropisomerism shown in tryptorubins, which are the founding members of the “atropitide” family. Therefore, we propose to use a new RiPP family name, “bitryptides”, for cihunamides, tryptorubins, and their congeners, wherein the Trp-Trp linkages define the structural class rather than non-canonical atropisomerism.     

Dictyoneolone,a B/C ring juncture-defused steroid from a Dictyonella sp. sponge

Dictyoneolone (1), a new secosteroid was isolated from a Dictyonella sp. sponge collected from Gageo-do, Korea. Based upon the results of combined spectroscopic analyses, the structure of this compound was determined to possess a highly unusual B/C ring juncture-defused moiety. The configurations of 1 were determined by a combination of proton-proton couplings and NOESY analyses. Dictyoneolone exhibited weak cytotoxicity against the K562 and A549 cancer cell lines.     

Zagreb indices of graphs

The first Zagreb index M₁(G) is equal to the sum of squares of the degrees of the vertices, and the second Zagreb index M₂(G) is equal to the sum of the products of the degrees of pairs of adjacent vertices of the underlying molecular graph G. In this paper, we obtain lower and upper bounds on the first Zagreb index M₁(G) of G in terms of the number of vertices (n), number of edges (m), maximum vertex degree (Δ), and minimum vertex degree (δ). Using this result, we find lower and upper bounds on M₂(G). Also, we present lower and upper bounds on M₂(G) +M₂(G) in terms of n, m, Δ, and δ, where G denotes the complement of G. Moreover, we determine the bounds on first Zagreb coindex M₁(G) and second Zagreb coindex M₂(G). Finally, we give a relation between the first Zagreb index and the second Zagreb index of graph G.