ALBERT

Notes: Summary The variant thyroxine-binding globulin in a family from Montreal (TBG-M) has a reduced affinity for thyroxine, shows a slight cathodal shift on isoelectric focusing, and has an increased susceptibility to inactivation by heat and acid. We present the molecular basis for TBG-M, deduced by sequencing the entire 1245-bp coding regions and intron/exon junctions of the TBG gene of an affected hemizygous male. A single nucleotide substitution in the codon for amino acid 113 of the mature protein (GCC to CCC) was found, resulting in the replacement of alanine by proline. The mutation was confirmed by allele-specific amplification of genomic DNA from the propositus and three other affected family members. Since point mutations throughout the molecule have been shown to alter the properties of variant TBGS, and because amino acid substitutions with proline are known to impair stability and function of proteins, the replacement of alanine 113 by proline provides a logical explanation for the observed properties of TBG-M.

Notes: Abstract Two closely related cysteine-rich hydrophobic proteins, Sc3p and Sc4p, of the basidiomycete Schizophyllum commune are developmentally regulated and associated with the walls of aerial hyphae and fruit-body hyphae. They are present in the walls as hot-SDS-insoluble complexes which can be extracted with formic acid. The hydrophobins can then be dissociated by oxidation with performic acid. However, extraction of the walls with trifluoroacetic acid results in both solubilization and dissociation of the hydrophobin complexes into monomers. This suggests that non-covalent interactions are responsible for formation of these insoluble complexes. Carboxymethylation with iodoacetic acid only occurred after reduction with DTT indicating all cysteines in the monomeric hydrophobins involved in intramolecular disulfide bridges. Abundant proteins with similar properties were found in walls from all other filamentous fungi tested, including the basidiomycetes Pleurotus ostreatus, Coprinus cinereus, Agaricus bisporus, and Phanerochaete chrysosporium, the ascomycetes Aspergillus nidulans, Neurospora crassa, and Penicillium chrysogenum, and the zygomycete Mucor mucedo.

Notes: SUMMARY. 1. Pore water chemistry in peaty sediment was monitored for a year at two representative locations of the eutrophic shallow Loosdrecht lakes. The Netherlands. Phosphorus fluxes over the sediment-water interface were calculated using measured concentration gradients in the pore water and compared to fluxes measured under laboratory conditions. Results were analysed with Redundancy Analysis to detect patterns of variation in pore water chemistry and in measured and calculated fluxes, that could be ascribed to environmental variables.2. It was demonstrated that phosphorus fluxes measured in long-term laboratory incubations were not correlated to any of the pore water characteristics.3. Initial phosphorus fluxes measured in sediment columns, which varied between −7.7 and 1330 μmol m−2: day−1, were correlated significantly to the calculated phosphorus flux over the sediment-water interface.4. The high correlation between calculated fluxes of ammonia, phosphorus and methane and measured initial flux of phosphorus, conclusively pointed to mineralization of organic matter as the driving force for phosphorus release from the sediment.5. Redundancy Analysis demonstrated that the rates of mineralization and phosphorus release were only weakly related to temperature. They appeared to be especially stimulated by the autumnal decrease in temperature which was probably related to an extra input of organic matter.

Notes: Abstract: Many different bacterial species produce lipases which hydrolyze esters of glycerol with preferably long-chain fatty acids. They act at the interface generated by a hydrophobic lipid substrate in a hydrophilic aqueous medium. A characteristic property of lipases is called interfacial activation, meaning a sharp increase in lipase activity observed when the substrate starts to form an emulsion, thereby presenting to the enzyme an interfacial area. As a consequence, the kinetics of a lipase reaction do not follow the classical Michaelis-Menten model. With only a few exceptions, bacterial lipases are able to completely hydrolyze a triacylglycerol substrate although a certain preference for primary ester bonds has been observed. Numerous lipase assay methods are available using coloured or fluorescent substrates which allow spectroscopic and fluorimetric detection of lipase activitiy. Another important assay is based on titration of fatty acids released from the substrate. Newly developed methods allow to exactly determine lipase activity via controlled surface pressure or by means of a computer-controlled oil drop tensiometer. The synthesis and secretion of lipases by bacteria is influenced by a variety of environmental factors like ions, carbon sources, or presence of non-metabolizable polysaccharides. The secretion pathway is known for Pseudomonas lipases with P. aeruginosa lipase using a two-step mechanism and P. fluorescens lipase using a one-step mechanism. Additionally, some Pseudomonas lipases need specific chaperone-like proteins assisting their correct folding in the periplasm. These lipase-specific foldases (Lif-proteins) which show a high degree of amino acid sequence homology among different Pseudomonas species are coded for by genes located immediately downstream the lipase structural genes. A comparison of different bacterial lipases on the basis of primary structure revealed only very limited sequence homology. However, determination of the three-dimensional structure of the P. glumae lipase indicated that at least some of the bacterial lipases will presumably reveal a conserved folding pattern called the α/β-hydrolase fold, which has been described for other microbial and human lipases. The catalytic site of lipases is buried inside the protein and contains a serine-protease-like catalytic triad consisting of the amino acids serine, histidine, and aspartate (or glutamate). The Ser-residue is located in a strictly conserved β-ε-Ser-α motif. The active site is covered by a lid-like a-helical structure which moves away upon contact of the lipase with its substrate, thereby exposing hydrophobic residues at the protein's surface mediating the contact between protein and substrate. This movable lid-like α-helix explains at a molecular level the lipase-specific phenomenon of interfacial activation. At least some of the pathogenic bacterial species produce a lipase which has been studied with respect to its role as a virulence factor. Lipases of Propionibacterium acnes and Staphylococcus epidermidis may be involved in colonization and persistence of these bacteria on the human skin. Lipases of S. aureus and P. aeruginosa are produced during the bacterial infection process and, at least in vitro, considerably impair the function of different cell types involved in the human immune response like macrophages or platelets. The present state of knowledge suggests to classify the lipases as important bacterial virulence factors which exert their harmful effects in combination with other bacterial enzymes, in particular the phospholipases C. Most of the steadily increasing interest in bacterial lipases is based on their biotechnological applications which are partly based on their potential to catalyze not only hydrolysis but also synthesis of a variety of industrially valuable products. Optically active compounds, various esters and lactones are among the substances synthesized using bacterial lipases. Recently, an important application emerged with the addition of bacterial lipases to household detergents in order to reduce or even replace synthetic detergent chemicals which pose considerable environmental problems. As a main conclusion, [ipases represent an extremely versatile group of bacterial extracellular enzymes that are capable of performing a variety of important reactions, thereby presenting a fascinating field tot future research.

Notes: Summary The double marsh marigold, Caltha palustris ‘Plena’ was introduced to cultivation by Clusius in Vienna from a meadow near Salzburg in the late sixteenth century. The plant entered cultivation in gardens in Austria and in southern Germany. It became a valued garden plant in collections of connaisseurs in Austria, Switzerland, Germany, England, Holland and Flanders. There it was noted by Jan Brueghel I, who painted it in many of his flower paintings. Several artists who worked in Antwerp used the plant as well, probably following Brueghel. Besides ‘Plena’ the cultivar Monstruosa was possibly known in the early seventeenth century. Further development of cultivated forms of Caltha palustris occurred around 1900 and more recently in England from about 1985 onwards. Double marsh marigolds are valued but minor plants in present day horticulture; their days of glory were in early seventeenth century flower painting.

Notes: Abstract We study two new cyclic reservation schemes for the efficient operation of systems consisting of a single server and multiple queues. The schemes are the Globally Gated regime and the Cyclic-Reservation Multiple-Access (CRMA). Both procedures possess mechanisms for prioritizing the queues and lend themselves to a closed-form analysis. The combination of these two properties allows for effective and efficient operation of the systems, for which we provide a thorough delay analysis and derive simple rules for optimal operation.