Lipase catalyzed esterification of glycidol in organic solvents

We studied the resolution of racemic glycidol through esterification with butyric acid catalyzed by porcine pancreatic lipase in organic media. A screening of seven solvents (log P values between 0.49 and 3.0, P being the n-octanol-water partition coefficient of the solvent) showed that neither log P nor the logarithm of the molar solubility of water in the solvent provides good correlations between enantioselectivity and the properties of the organic media. Chloroform was one of the best solvents as regards the enantiomeric purity (e. p.) of the ester produced. In this solvent, the optimum temperature for the reaction was determined to be 35 degrees C. The enzyme exhibited maximum activity at a water content of 13 +/- 2% (w/w). The enantiomeric purity obtained was 83 +/- 2% of (S)-glycidyl butyrate and did not depend on the alcohol concentration or the enzyme water content for values of these parameters up to 200 mM and 25% (w/w), respectively. The reaction was found to follow a BiBi mechanism. (c) 1993 John Wiley & Sons, Inc.     

A strategy for the characterization of minute chromosome rearrangements using multiple color fluorescence in situ hybridization with chromosome-specific DNA libraries and YAC clones

The identification of marker chromosomes in clinical and tumor cytogenetics by chromosome banding analysis can create problems. In this study, we present a strategy to define minute chromosomal rearrangements by multicolor fluorescence in situ hybridization (FISH) with whole chromosome painting probes derived from chromosome-specific DNA libraries and Alu-polymerase chain reaction (PCR) products of various region-specific yeast artificial chromosome (YAC) clones. To demonstrate the usefulness of this strategy for the characterization of chromosome rearrangements unidentifiable by banding techniques, an 8p+ marker chromosome with two extra bands present in the karyotype of a child with multiple anomalies, malformations, and severe mental retardation was investigated. A series of seven-color FISH experiments with sets of fluorochrome-labeled DNA library probes from flow-sorted chromosomes demonstrated that the additional segment on 8p+ was derived from chromosome 6. For a more detailed characterization of the marker chromosome, three-color FISH experiments with library probes specific to chromosomes 6 and 8 were performed in combination with newly established telomeric and subtelomeric YAC clones from 6q25, 6p23, and 8p23. These experiments demonstrated a trisomy 6pter6p22 and a monosomy 8pter8p23 in the patient. The present limitations for a broad application of this strategy and its possible improvements are discussed.Dedicated to Professor Dr. U. Wolf on the occasion of his 60th birthday     

Litter and soil biodiversity jointly drive ecosystem functions

The decomposition of litter and the supply of nutrients into and from the soil are two fundamental processes through which the above- and belowground world interact. Microbial biodiversity, and especially that of decomposers, plays a key role in these processes by helping litter decomposition. Yet the relative contribution of litter diversity and soil biodiversity in supporting multiple ecosystem services remains virtually unknown. Here we conducted a mesocosm experiment where leaf litter and soil biodiversity were manipulated to investigate their influence on plant productivity, litter decomposition, soil respiration, and enzymatic activity in the littersphere. We showed that both leaf litter diversity and soil microbial diversity (richness and community composition) independently contributed to explain multiple ecosystem functions. Fungal saprobes community composition was especially important for supporting ecosystem multifunctionality (EMF), plant production, litter decomposition, and activity of soil phosphatase when compared with bacteria or other fungal functional groups and litter species richness. Moreover, leaf litter diversity and soil microbial diversity exerted previously undescribed and significantly interactive effects on EMF and multiple individual ecosystem functions, such as litter decomposition and plant production. Together, our work provides experimental evidence supporting the independent and interactive roles of litter and belowground soil biodiversity to maintain ecosystem functions and multiple services.     

Isolation and culture of rat superior mesenteric artery smooth muscle cells

Summary The structure and function of vascular smooth muscle cells have been extensively investigated with the aid of in vitro culture techniques. The majority of studies have utilized aortic tissue as the source of cells. We present here a method for isolating and culturing smooth muscle cells of the rat superior mesenteric artery, an elasto-muscular vessel that is structurally and functionally different from the aorta. Cells were isolated from partially digested explants and characterized by immunochemical and biochemical techniques. Unlike cultured fibroblasts, the cultured cells stained positive for smooth muscle specific actin. The cells also produced laminin and type IV collagen in culture. This method provides a means for the isolation of large numbers of viable smooth muscle cells from the superior mesenteric artery which can be propagated in culture for in vitro study.     

Horizontal biosedimentary gradients across the Sado estuary,W. Portugal

The topography of the Sado estuary, the second largest of Portugal, comprises the outer estuary inside the entrance channel and the inner estuary, on the inward side of which begins the tidal mudflats. The outer estuary subtidal area covers approximately 70 km² and presents a series of longitudinal intertidal sandbanks, separating a northern and a southern channel. A benthic survey was undertaken in the outer estuary during June 1986, in which superficial sediments and macrofauna were sampled at 133 locations. The environmental variables measured in the superficial sediments were the temperature, the granulometric structure, the silt, sand and the gravel content, and the total organic matter content. The primary macrofauna biological variables studied were the species composition, abundance and biomass, calculated on wet, dry and ash-free dry weight. The granulometry and the organic content of superficial sediments agreed with the transient and the residual currents velocity field, simulated in a 2-D hydrodynamic model previously elaborated for the outer estuary. The northern channel superficial sediments showed higher silt and total organic matter content, while the model also suggested lower transient and residual velocities, water flow and shear stress in this channel. The distribution patterns of the subtidal macrofauna were separated into two main groups of species, one comprising taxa essentially settled near the estuarine mouth and the other inwards. Biological primary variables also showed consistent patterns, comparable to other Portuguese estuaries. The major subtidal benthic biotopes were obtained through classification analysis and related to the prevailing hydrophysical and sedimentary conditions in the outer estuary.     

The conjugative plasmid SLP2 of Streptomyces lividans is a 50 kb linear molecule

The SLP2 plasmid had previously been demonstrated genetically to exist In Streptomyces lividans by its ability to promote conjugation and to elicit‘pocks’on recipient (SLP2^?) cultures, but it had not been physically detected. Using pulsed-field gel electrophoresis, a 50kb linear DNA was isolated from SLP2⁺ but not SLP2^? strains of S. lividans, and from Streptomyces coelicolor and Streptomyces parvulus strains to which SLP2 had been transferred by conjugation or transformation. We conclude that this linear DNA is SLP2. The terminal fragments of SLP2 were cloned. The determined sequences revealed a 44 bp imperfect terminal inverted repeat. The terminal 12 bp sequence of SLP2 was identical to those of two other Streptomyces linear plasmids, pSLA2 and pSCL, and similar to the terminal sequences of another Streptomyces linear plasmid, SCP1. The termini of SLP2 DNA were resistant to digestion by λ exonuclease and ExoIII. A truncated (probably crippled) copy of Tn4811 is present on the plasmid. While the SLP2 plasmid exists as a tree form in the host, a 15.7 kb sequence corresponding to the segment of SLP2 from Tn4811 to the right terminus is also present (at a copy number similar to the free form) elsewhere in the genome of S. lividans. Furthermore, SLP2 is partially homologous to a newly discovered 650 kb linear plasmid in S. parvulus.     

Diol sulfonamides: A potent and novel class of inhibitors of human renin

The syntheses and pharmacological activity of a series of diol sulfonamides which function as inhibitors of human renin are described. The most potent compound in this series, compound 20 (SQ 33,800), is a subnanomolar inhibitor of human renin (IC₅₀ = 0.35 × 10⁻⁹ M).     

Am improved procedure for the isolation of chloroplast DNA fromChlamydomonas reinhardtii

The isolation of chloroplast DNA fromChlamydomonas reinhardtii requires the efficient separation of this AT-rich genome from the GC-rich nuclear genome by density-gradient centrifugation. We describe a simple and efficient method for separating these DNA fractions by using a sodium iodide gradient in combination with the DNA-binding dye, bisbenzimide. The yield of chloroplast DNA is close to the theoretical maximum and the DNA is suitable for restriction enzyme analysis and cloning. This method is applicable to the isolation of AT-rich plastid genomes from other organisms and may be appropriate as a general method for separating species of DNA that differ in their AT/GC ratios. An erratum to this article is available at .     

Effects of temperature and nutrients on microscopic stages of the bull kelp (Nereocystis luetkeana,Phaeophyceae)

Warming ocean temperatures have been linked to kelp forest declines worldwide, and elevated temperatures can act synergistically with other local stressors to exacerbate kelp loss. The bull kelp Nereocystis luetkeana is the primary canopy-forming kelp species in the Salish Sea, where it is declining in areas with elevated summer water temperatures and low nutrient concentrations. To determine the interactive effects of these two stressors on microscopic stages of N. luetkeana, we cultured gametophytes and microscopic sporophytes from seven different Salish Sea populations across seven different temperatures (10–22°C) and two nitrogen concentrations. The thermal tolerance of microscopic gametophytes and sporophytes was similar across populations, and high temperatures were more stressful than low nitrogen levels. Additional nitrogen did not improve gametophyte or sporophyte survival at high temperatures. Gametophyte densities were highest between 10 and 16°C and declined sharply at 18°C, and temperatures of 20 and 22°C were lethal. The window for successful sporophyte production was narrower, peaking at 10–14°C. Across all populations, the warmest temperature at which sporophytes were produced was 16 or 18°C, but sporophyte densities were 78% lower at 16°C and 95% lower at 18°C compared to cooler temperatures. In the field, bottom temperatures revealed that the thermal limits of gametophyte growth (18°C) and sporophyte production (16–18°C) were reached during the summer at multiple sites. Prolonged exposure of bull kelp gametophytes to temperatures of 16°C and above could limit reproduction, and therefore recruitment, of adult kelp sporophytes.     

Influence of seasonal variation to the population growth and ecophysiology of Typha domingensis (Typhaceae)

Journal of Plant Research - Precipitation is an important climatic element that defines the hydrological regime, and its seasonal variation produces annual dry and wet periods in some areas. This...