Isolation of three new naturally occurring compounds from the culture of Micromonospora sp. P1068

Bioassay guided isolation of an antibacterial extract prepared from the fermentation broth of a Micromonospora sp. P1068 led to the isolation of eight compounds identified as (3R) 3,4',7-trihydroxy-isoflavanone (1), 3-hydroxydehydrodaidzein, daidzein (2), 3-methyl-1H-indole-2-carboxylic acid (3), 1H-indole-3-carboxaldehyde (4), 3-(p-hydroxyphenyl)-N-methylpropionamide, N-methylphloretamide (5), phenyl acetic acid (6), 2-hydroxy phenyl acetic acid (7) and 4-hydroxy-5-methoxy-benzoic acid (8). Compounds 1 and 5 were found to be novel chemical entities while 3 was isolated from a natural source for the first time. All compounds were evaluated for their antimicrobial activities against a panel of clinically significant microorganisms. Compound 4 was active against Staphylococcus aureus (MIC, 32 microg/ml), Enterococcus faecium (MIC, 32 microg/ml) and Escherichia coli (MIC, 64 microg/ml).     

Links between microscopic and macroscopic fluid mechanics

The microscopic and macroscopic versions of fluid mechanics differ qualitatively. Microscopic particles obey time-reversible ordinary differential equations. The resulting particle trajectories {q(t)} may be time-averaged or ensemble-averaged so as to generate field quantities corresponding to macroscopic variables. On the other hand, the macroscopic continuum fields described by fluid mechanics follow irreversible partial differential equations. Smooth particle methods bridge the gap separating these two views of fluids by solving the macroscopic field equations with particle dynamics that resemble molecular dynamics. Recently, nonlinear dynamics have provided some useful tools for understanding the relationship between the microscopic and macroscopic points of view. Chaos and fractals play key roles in this new understanding. Non-equilibrium phase-space averages look very different from their equilibrium counterparts. Away from equilibrium the smooth phase-space distributions are replaced by fractional-dimensional singular distributions that exhibit time irreversibility.     

Gaussian Property of the Rings R(X) and R〈X〉

The content of a polynomial f over a commutative ring R is the ideal c(f) of R generated by the coefficients of f. A commutative ring R is said to be Gaussian if c(fg) = c(f)c(g) for every polynomials f and g in R[X]. A number of authors have formulated necessary and sufficient conditions for R(X) (respectively, R?X?) to be semihereditary, have weak global dimension at most one, be arithmetical, or be Prüfer. An open question raised by Glaz is to formulate necessary and sufficient conditions that R(X) (respectively, R?X?) have the Gaussian property. We give a necessary and sufficient condition for the rings R(X) and R?X? in terms of the ring R in case the square of the nilradical of R is zero.     

Brocaenols A-C: novel polyketides from a marine derived Penicillium brocae

Chemical investigation of a Penicillium brocae, obtained from a tissue sample of a Fijian Zyzyya sp. sponge, yielded two known diketopiperazines and three novel cytotoxic polyketides, brocaenols A-C. The brocaenols contain an unusual enolized oxepine lactone ring system that to the best of our knowledge is unprecedented in the literature. The structures were elucidated by using 2D-NMR methods including an INADEQUATE experiment. The absolute stereochemistry of brocaenol A was established by using a modified Mosher method. The taxonomy of the producing fungus was elucidated by using both morphological and rDNA sequence analysis.     

Kalihinols from two Acanthella cavernosa sponges: inhibitors of bacterial folate biosynthesis

Acanthella spp. sponges have been prolific sources of highly functionalized diterpene antibiotics. Two Acanthella cavernosa sponges were investigated based on the activity of their extracts in a screen designed to detect bacterial folate biosynthesis inhibitors. Bacillus subtilis PY79 strain harboring a lacZ reporter gene fusion to a trimethoprim-responsive promoter (PpanB) was used for the screen. The ability of kalihinols to inhibit bacterial folate biosynthesis was investigated resulting in preliminary structure activity relationships. Eight kalihinol type diterpenes were isolated from two Philippine Acanthella cavernosa specimens including two new 10- and 15-formamido-kalihinol F analogs.     

Solubilization chromatography: Ethers,carboxylic acids,and hydrocarbons

Synthetic mixtures of aliphatic and aromatic ethers, satmated fatty acids, and substituted benzenes and naphthalenes were separated by elution through columns of ion-exchange resins with aqueous solutions of acetic acid as eluent An attempt was made to use a resin of low capacity for the separation of such mixtures, and the results of this attempt are used to help elucidate the theory of solubilization chromatography     

Rapid catalytic oxidation of CO to CO(2) - On the development of a new approach to on-line oxygen isotope analysis of organic matter

A new approach to on-line oxygen isotope analysis has been developed which utilises existing elemental analyser and mass spectrometry technology to produce a sample of carbon dioxide gas for oxygen isotople analysis. The method relies on on-line high temperature pyrolysis of the sample over a carbon source followed by a rapid, non-contributive partial catalytic oxidation over nickel powder at between 550 and 600 degrees C. Initial results demonstrate both good precision (better than 0.2 per thousand) and accuracy for both cellulose and silver nitrate samples. Copyright 1999 John Wiley & Sons, Ltd.     

The origin and elimination of spurious peaks in threshold electron photoionization spectra

Autoionization electrons in threshold photoionization spectra are known to occur. The effect of such electrons on the interpretation of threshold electron spectra is discussed and a new method is described which enables one to discriminate between zero kinetic energy electrons and energetic electrons in photoionization experiments with little ambiguity. The method largely overcomes the main problem present in some previously described threshold electron studies; namely, the line-of-sight transmission of energetic electrons which gives rise to non-threshold electron peaks. A rejection ratio of 25 is readily obtained for 0.038 eV electrons compared with threshold (zero kinetic energy) electrons and the (small) transition probability for energetic electrons falls off more rapidly than for analysers previously described. Design parameters based on electron trajectory calculations are given for the analyser used, and photoionization results on argon are presented.