Rapid fluorometric detection for completeness in solid phase coupling reactions

The fluorescamine test for the rapid detection of trace amounts of uncoupled products from solid phase peptide synthesis is reported. This novel procedure can detect much smaller amounts of incomplete coupling with greater simplicity than has previously been possible. Since the test is carried out under mild conditions certain side reactions are circumvented. The fluorophor-resins are easily viewed under long wave ultraviolet light, are stable at room temperature, and may be used for quantitative evaluation.     

Long range physical cell-to-cell signalling via mitochondria inside membrane nanotubes: a hypothesis

Coordinated interaction of single cells by cell-to-cell communication (signalling) enables complex behaviour necessary for the functioning of multicellular organisms. A quite newly discovered cell-to-cell signalling mechanism relies on nanotubular cell-co-cell connections, termed “membrane nanotubes” (MNTs). The present paper presents the hypothesis that mitochondria inside MNTs can form a connected structure (mitochondrial network) which enables the exchange of energy and signals between cells. It is proposed that two modes of energy and signal transmission may occur: electrical/electrochemical and electromagnetic (optical). Experimental work supporting the hypothesis is reviewed, and suggestions for future research regarding the discussed topic are given.     

Effects of topographic variability on the scaling of plant species richness in gradient dominated landscapes

It is commonly assumed that variation in abiotic site conditions influences the number of niches, which in turn affects the potential species richness in an area. Based on theoretical considerations, abiotic variation is often used as an estimator of species richness at broad scales, while at finer landscape scales the diversity of habitat types is used. However, habitat estimators assume the landscape to be composed of discrete, homogeneous patches with sharp boundaries, and such a concept is hard to apply in gradient-dominated landscapes. The aim of this study was therefore to investigate the influence of topographic variability (TV) on species richness at the landscape level (gamma (γ) diversity) and on its components (alpha (α) and beta (β) diversity) at microsite and habitat group levels. Using floristic data from 12 "landscapes" of 1 km² we investigated the influence on diversity components of two simple and one complex measures of TV. While the standard deviation (SD) of altitude explained a high proportion of the variation in γ diversity (linear regression model, R²=0.63), the complex measure, SD of solar radiation explained it even better (R²=0.82). There were strong effects of TV on α and β diversity components at the microsite level, but only marginal increases of the diversity components at the habitat level. Further analyses revealed that the missing increase of the habitat level components was caused by differences between habitat groups and that only grassland diversity components increased significantly with TV. We conclude that TV at a landscape scale has strong effects on niche or microsite diversity and is an appropriate estimator of relative species richness in landscapes that are topographically heterogeneous and gradient dominated.     

The age of fine-root carbon in three forests of the eastern United States measured by radiocarbon

Using a new approach involving one-time measurements of radiocarbon (¹⁴C) in fine (<2 mm diameter) root tissues we have directly measured the mean age of fine-root carbon. We find that the carbon making up the standing stock of fine roots in deciduous and coniferous forests of the eastern United States has a mean age of 3-18 years for live fine roots, 10-18 years for dead fine roots, and 3-18 years for mixed live+dead fine roots. These ¹⁴C-derived mean ages represent the time C was stored in the plant before being allocated for root growth, plus the average lifespan (for live roots), plus the average time for the root to decompose (for dead roots and mixtures). Comparison of the ¹⁴C content of roots known to have grown within 1 year with the ¹⁴C of atmospheric CO₂ for the same period shows that root tissues are derived from recently fixed carbon, and the storage time prior to allocation is <2 years and likely <1 year. Fine-root mean ages tend to increase with depth in the soil. Live roots in the organic horizons are made of C fixed 3-8 years ago compared with 11-18 years in the mineral B horizons. The mean age of C in roots increases with root diameter and also is related to branching order. Our results differ dramatically from previous estimates of fine-root mean ages made using mass balance approaches and root-viewing cameras, which generally report life spans (mean ages for live roots) of a few months to 1-2 years. Each method for estimating fine-root dynamics, including this new radiocarbon method, has biases. Root-viewing approaches tend to emphasize more rapidly cycling roots, while radiocarbon ages tend to reflect those components that persist longest in the soil. Our ¹⁴C-derived estimates of long mean ages can be reconciled with faster estimates only if fine-root populations have varying rates of root mortality and decomposition. Our results indicate that a standard definition of fine roots, as those with diameters of <2 mm, is inadequate to determine the most dynamic portion of the root population. Recognition of the variability in fine-root dynamics is necessary to obtain better estimates of belowground C inputs.     

Fast estimation of ATP/ADP ratio as a special step in pharmacological and toxicological studies using the cell-free translation systems

We have developed a simple and effective reversed-phase HPLC procedure for rapid estimation of the ATP/ADP ratio in a cell-free translation system containing creatine kinase. Analysis of the acetone-extractable pool derived from a reticulocyte lysate cell-free system was carried out by automatic chromatography on S5CN-ODS stationary phase using a linear 10-65% pyridine elution gradient formed on the basis of methanol/water (9:1, v/v) mobile phase. This method was used to detect and characterize the inhibition of translation induced by considerable suppression of ATP resynthesis in vitro. It was shown that methyl mercury, unlike cycloheximide, pactamycin, CCl4 and barbituric acid, exerts inhibitory effect on the ATP regeneration in a cell-free translation system.     

Microbial oxidation of methane and methanol: crystallization and properties of methanol dehydrogenase from Methylosinus sporium.

Obligate methylotrophs are divisible into two types on the basis of ultrastructural biochemical characteristics. Both groups possess a soluble phenazine methosulfate (PMS)-dependent methanol dehydrogenase. In addition, particulate PMS-dependent methanol dehydrogenase and PMS-independent methanol oxidase have been found in the type I membrane group. A procedure was developed for the crystallization of methanol dehydrogenase from the soluble fraction of the type II obligate methylotroph Methylosinus sporium. This is the first report of a crystalline methanol dehydrogenase from a methylotrophic bacterium. The crystallized enzyme is homogeneous as judged by ultracentrifugation and by acrylamide gel electrophoresis. In the presence of an electron acceptor (phenazine or phenazinium compound) and an activator (ammonium compound), the crystallized enzyme catalyzed the oxidation of primary alcohols and formaldehyde. Secondary, tertiary, and aromatic alcohols were not oxidized. The molecular weight of the enzyme as estimated by gel filtration is approximately 60,000, and as estimated by sedimentation equilibrium analysis it is 62,000. The sedimentation constant (S20,W) is 2.9. The subunit size determined by sodium dodecyl sulfate-gel electrophoresis is approximately 60,000. The amino acid composition and spectral properties of the enzyme are also presented. Antisera prepared against the crystalline enzyme are nonspecific, they cross-reacted and inhibited isofunctional enzymes from other obligate methylotrophic bacteria.