L.L.M. Van Deenen

Bio: L.L.M. Van Deenen is an academic researcher from Utrecht University. The author has contributed to research in topics: Phosphatidylcholine & Phospholipid. The author has an hindex of 87, co-authored 280 publications receiving 23747 citations.

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Abstract: Gram-negative bacteria characteristically are surrounded by an additional membrane layer, the outer membrane. Although outer membrane components often play important roles in the interaction of symbiotic or pathogenic bacteria with their host organisms, the major role of this membrane must usually be to serve as a permeability barrier to prevent the entry of noxious compounds and at the same time to allow the influx of nutrient molecules. This review summarizes the development in the field since our previous review (H. Nikaido and M. Vaara, Microbiol. Rev. 49:1-32, 1985) was published. With the discovery of protein channels, structural knowledge enables us to understand in molecular detail how porins, specific channels, TonB-linked receptors, and other proteins function. We are now beginning to see how the export of large proteins occurs across the outer membrane. With our knowledge of the lipopolysaccharide-phospholipid asymmetric bilayer of the outer membrane, we are finally beginning to understand how this bilayer can retard the entry of lipophilic compounds, owing to our increasing knowledge about the chemistry of lipopolysaccharide from diverse organisms and the way in which lipopolysaccharide structure is modified by environmental conditions.

Bilirubin is an antioxidant of possible physiological importance

Abstract: Bilirubin, the end product of heme catabolism in mammals, is generally regarded as a potentially cytotoxic, lipid-soluble waste product that needs to be excreted. However, it is here that bilirubin, at micromolar concentrations in vitro, efficiently scavenges peroxyl radicals generated chemically in either homogeneous solution or multilamellar liposomes. The antioxidant activity of bilirubin increases as the experimental concentration of oxygen is decreased from 20% (that of normal air) to 2% (physiologically relevant concentration). Furthermore, under 2% oxygen, in liposomes, bilirubin suppresses the oxidation more than alpha-tocopherol, which is regarded as the best antioxidant of lipid peroxidation. The data support the idea of a "beneficial" role for bilirubin as a physiological, chain-breaking antioxidant.

4 Lipid and Cell-Wall Analysis in Bacterial Systematics

Abstract: Publisher Summary Recent advances in the biochemistry of microorganisms have revealed that cell-component analysis can be effectively applied to bacterial systematics, providing the basis of chemotaxonomy. Analyses of cell components are coming to be essential tools not only for bacterial classification but also for identification. The sequence of chromosomal DNA holds the essential genetic information for an organism. Phylogenetic relationships are often examined using data on nucleotide sequences of ribosomal RNA. However, it is still impossible to determine the sequences of large polynucleotides for the number of organisms sufficient for taxonomic purposes. DNA (RNA) homologies, which have been applied to various kinds of bacteria, present useful information on bacterial systematics. Homology indices are values used in comparing microorganisms. DNA homology data contribute to the clarification, not only of the relatedness of two organisms, but also of the evaluation of phenotypic characteristics.