Structure and dynamics of Yukawa dusty plasmas and dusty plasma mixtures

Dusty plasmas can be regarded as Yukawa system in a one-dimensional potential well. We extend the analysis on dusty plasmas to the two-dimensional Yukawa particles. At low temperatures, dust particles sit in a plane which is perpendicular to the gravitational field under appropriate conditions. When they are also confined laterally by an electrode, we have a finite two-dimensional system of Yukawa particles. The low temperature structures are obtained by molecular dynamics simulations and the results are reproduced by theoretical analyses. The correlation energy of the Yukawa particles has been shown to play an essential role in structure formations. As for dynamics of this system, the tendency of a change from the surface melting in systems with short-ranged interactions to possible surface freezing of Coulombic system is observed

The first sorbicillinoid alkaloids, the antileucemic sorbillactones A and B, from a sponge derived Penicillium chrysogenum strain

The saltwater culture of a Penicillium chrysogenum strain isolated from the Mediterranean sponge Ircinia fasciculata yielded three new sorbicillin-derived compounds (1-3), whose structures were elucidated mainly by 2D NMR and mass spectrometry. Among them, sorbicillactones A (1) and B (2) are the first sorbicillinoid natural products that contain nitrogen. Compound 1 is anti-HIV active and it exhibits a strong cytotoxic activity against L5178y leukemic cells, combined with a relatively low toxicity to cervical carcinoma HeLa S3 cells and pheochromocytoma PC 12 cells. The absolute configurations of I and 2 were elucidated by quantum chemical calculation of circular dichroism (CD) spectra. Another compound isolated, sorbivinetone (3), might be an artifact derived from sorbicillinol (4) by Diels-Alder reaction with ethyl vinyl ether. Furthermore, the known sorbicillinoid fungal metabolites oxosorbicillinol (5), sorbicillin (6), and bisvertinolone (7) were identified, as well as the alkaloids meleagrine and roquefortine C. The biosynthetic origin of sorbicillactone A (1) from acetate, alanine, and methionine was investigated by feeding experiments with C-13-labeled precursor