Dick B. Janssen

Bio: Dick B. Janssen is an academic researcher from University of Groningen. The author has contributed to research in topics: Haloalkane dehalogenase & Dehalogenase. The author has an hindex of 76, co-authored 374 publications receiving 18485 citations. Previous affiliations of Dick B. Janssen include Radboud University Nijmegen & Codexis.

Degradation of chlorinated aliphatic hydrocarbons by Methylosinus trichosporium OB3b expressing soluble methane monooxygenase.

Abstract: Degradation of trichloroethylene (TCE) by the methanotrophic bacterium Methylosinus trichosporium OB3b was studied by using cells grown in continuous culture. TCE degradation was a strictly cometabolic process, requiring the presence of a cosubstrate, preferably formate, and oxygen. M. trichosporium OB3b cells degraded TCE only when grown under copper limitation and when the soluble methane monooxygenase was derepressed. During TCE degradation, nearly total dechlorination occurred, as indicated by the production of inorganic chloride, and only traces of 2,2,2-trichloroethanol and trichloroacetaldehyde were produced. TCE degradation proceeded according to first-order kinetics from 0.1 to 0.0002 mM TCE with a rate constant of 2.14 ml min-1 mg of cells-1. TCE concentrations above 0.2 mM inhibited degradation in cell suspensions of 0.42 mg of cells ml-1. Other chlorinated aliphatics were also degraded by M. trichosporium OB3b. Dichloromethane, chloroform, 1,1-dichloroethane, and 1,2-dichloroethane were completely degraded, with the release of stoichiometric amounts of chloride. trans-1,2-Dichloroethylene, cis-1,2-dichloroethylene, and 1,2-dichloropropane were completely converted, but not all the chloride was released because of the formation of chlorinated intermediates, e.g., trans-2,3-dichlorooxirane, cis-2,3-dichlorooxirane, and 2,3-dichloropropanol, respectively. 1,1,1-Trichloroethane, 1,1-dichloroethylene, and 1,3-dichloropropylene were incompletely converted, and the first compound yielded 2,2,2-trichloroethanol as a chlorinated intermediate. The two perchlorinated compounds tested, carbon tetrachloride and tetrachloroethylene, were not converted.

Recent advances in the catalytic asymmetric synthesis of β-amino acids

Abstract: In this critical review, the progress in catalytic asymmetric synthesis of β-amino acids is discussed, covering the literature since 2002. The review treats transition metal catalysis, organocatalysis and biocatalysis and covers the most important synthetic methods, such as hydrogenation, the Mannich reaction and conjugate additions (160 references).

Degradation of halogenated aliphatic compounds by Xanthobacter autotrophicus GJ10.

Abstract: A bacterium that is able to utilize a number of halogenated short-chain hydrocarbons and halogenated carboxylic acids as sole carbon source for growth was identified as a strain of Xanthobacter autotrophicus. The organism constitutively produces two different dehalogenases. One enzyme is specific for halogenated alkanes, whereas the other, which is more heat stable and has a higher pH optimum, is specific for halogenated carboxylic acids. Haloalkanes were hydrolyzed in cell extracts to produce alcohols and halide ions, and a route for the metabolism of 1,2-dichloroethane is proposed. Both dehalogenases show a broad substrate specificity, allowing the degradation of bromine- and chlorine-substituted organic compounds. The results show that X. autotrophicus may play a role in the degradation of organochlorine compounds and that hydrolytic dehalogenases may be involved in the microbial metabolism of short-chain halogenated hydrocarbons in microorganisms.

Biocatalysis by dehalogenating enzymes

Abstract: Publisher Summary This chapter discusses dehalogenase enzymes and its types. The chapter emphasizes on the microbial origin and distribution of these enzymes, their biochemical properties, and their engineering and use in biocatalysis. Dehalogenases comprise a diverse group of enzymes belonging to different phylogenetic and mechanistic classes. They have biotechnological potential because of their high-catalytic power in the cleavage of carbon–halogen bonds of toxic environmental pollutants. Dehalogenases appear with very different structural folds, reaction types, and catalytic mechanisms. For example, several reductive dehalogenases that replace a chlorine substituent by a hydrogen possess a corrinoid cofactor typical for an electron transfer mechanism, whereas haloalkane dehalogenases belong to the α/β-hydrolase fold family, a group of proteins of which most members catalyze hydrolytic reactions via a covalent alkyl-enzyme intermediate, reminiscent to the acyl-enzyme intermediate of classical serine proteases. More recently, dehalogenases have been further explored for enantioselective conversion of other halocarboxylic acids and their esters and haloalkanes, as well as for their applicability in recycling and detoxifying trichloropropane.

Kinetics of Chlorinated Hydrocarbon Degradation by Methylosinus trichosporium OB3b and Toxicity of Trichloroethylene

Abstract: The kinetics of the degradation of trichloroethylene (TCE) and seven other chlorinated aliphatic hydrocarbons by Methylosinus trichosporium OB3b were studied. All experiments were performed with cells grown under copper stress and thus expressing soluble methane monooxygenase. Compounds that were readily degraded included chloroform, trans-1,2-dichloroethylene, and TCE, with Vmax values of 550, 330, and 290 nmol min-1 mg of cells-1, respectively. 1,1-Dichloroethylene was a very poor substrate. TCE was found to be toxic for the cells, and this phenomenon was studied in detail. Addition of activated carbon decreased the acute toxicity of high levels of TCE by adsorption, and slow desorption enabled the cells to partially degrade TCE. TCE was also toxic by inactivating the cells during its conversion. The degree of inactivation was proportional to the amount of TCE degraded; maximum degradation occurred at a concentration of 2 mumol of TCE mg of cells-1. During conversion of [14C]TCE, various proteins became radiolabeled, including the alpha-subunit of the hydroxylase component of soluble methane monooxygenase. This indicated that TCE-mediated inactivation of cells was caused by nonspecific covalent binding of degradation products to cellular proteins.

Cd-hit: a fast program for clustering and comparing large sets of protein or nucleotide sequences

Abstract: Motivation: In 2001 and 2002, we published two papers (Bioinformatics, 17, 282--283, Bioinformatics, 18, 77--82) describing an ultrafast protein sequence clustering program called cd-hit. This program can efficiently cluster a huge protein database with millions of sequences. However, the applications of the underlying algorithm are not limited to only protein sequences clustering, here we present several new programs using the same algorithm including cd-hit-2d, cd-hit-est and cd-hit-est-2d. Cd-hit-2d compares two protein datasets and reports similar matches between them; cd-hit-est clusters a DNA/RNA sequence database and cd-hit-est-2d compares two nucleotide datasets. All these programs can handle huge datasets with millions of sequences and can be hundreds of times faster than methods based on the popular sequence comparison and database search tools, such as BLAST. Availability: http://cd-hit.org Contact: [email protected]

“Bioinformatics” 특집을 내면서

Abstract: BIOE 402. Medical Technology Assessment. 2 or 3 hours. Bioentrepreneur course. Assessment of medical technology in the context of commercialization. Objectives, competition, market share, funding, pricing, manufacturing, growth, and intellectual property; many issues unique to biomedical products. Course Information: 2 undergraduate hours. 3 graduate hours. Prerequisite(s): Junior standing or above and consent of the instructor.

Methods in Enzymology.

Abstract: I read this book the same weekend that the Packers took on the Rams, and the experience of the latter event, obviously, colored my judgment. Although I abhor anything that smacks of being a handbook (like, \"How to Earn a Merit Badge in Neurosurgery\") because too many volumes in biomedical science already evince a boyscout-like approach, I must confess that parts of this volume are fast, scholarly, and significant, with certain reservations. I like parts of this well-illustrated book because Dr. Sj6strand, without so stating, develops certain subjects on technique in relation to the acquisition of judgment and sophistication. And this is important! So, given that the author (like all of us) is somewhat deficient in some areas, and biased in others, the book is still valuable if the uninitiated reader swallows it in a general fashion, realizing full well that what will be required from the reader is a modulation to fit his vision, propreception, adaptation and response, and the kind of problem he is undertaking. A major deficiency of this book is revealed by comparison of its use of physics and of chemistry to provide understanding and background for the application of high resolution electron microscopy to problems in biology. Since the volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of The instrument and its ancillary tools are simply and well presented. The potential use of chemical or cytochemical information as it relates to biological fine structure , however, is quite deficient. I wonder when even sophisticated morphol-ogists will consider fixation a reaction and not a technique; only then will the fundamentals become self-evident and predictable and this sine qua flon will become less mystical. Staining reactions (the most inadequate chapter) ought to be something more than a technique to selectively enhance contrast of morphological elements; it ought to give the structural addresses of some of the chemical residents of cell components. Is it pertinent that auto-radiography gets singled out for more complete coverage than other significant aspects of cytochemistry by a high resolution microscopist, when it has a built-in minimal error of 1,000 A in standard practice? I don't mean to blind-side (in strict football terminology) Dr. Sj6strand's efforts for what is \"routinely used in our laboratory\"; what is done is usually well done. It's just that …

Animals in a bacterial world, a new imperative for the life sciences

Abstract: In the last two decades, the widespread application of genetic and genomic approaches has revealed a bacterial world astonishing in its ubiquity and diversity. This review examines how a growing knowledge of the vast range of animal–bacterial interactions, whether in shared ecosystems or intimate symbioses, is fundamentally altering our understanding of animal biology. Specifically, we highlight recent technological and intellectual advances that have changed our thinking about five questions: how have bacteria facilitated the origin and evolution of animals; how do animals and bacteria affect each other’s genomes; how does normal animal development depend on bacterial partners; how is homeostasis maintained between animals and their symbionts; and how can ecological approaches deepen our understanding of the multiple levels of animal–bacterial interaction. As answers to these fundamental questions emerge, all biologists will be challenged to broaden their appreciation of these interactions and to include investigations of the relationships between and among bacteria and their animal partners as we seek a better understanding of the natural world.