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Copper-containing nitrite reductase from Pseudomonas aureofaciens is functional in a mutationally cytochrome cd 1-free background (NirS−) of Pseudomonas stutzeri (1993)

Glockner, Andrea B. ; Jüngst, Angelika ; Zumft, Walter G.

Springer

Archives of microbiology 160 (1993), S. 18-26

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ISSN: 1432-072X

Keywords: Nucleotide sequence ; Apocytochrome cd 1 ; Heme d 1 incorporation ; Denitrification ; Copper coordination ; Signal peptide ; Escherichia coli

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The structural gene, nirK, for the respiratory Cu-containing nitrite reductase from denitrifying Pseudomonas aureofaciens was isolated and sequenced. It encodes a polypeptide of 363 amino acids including a signal peptide of 24 amino acids for protein export. The sequence showed 63.8% positional identity with the amino acid sequence of “Achromobacter cycloclastes” nitrite reductase. Ligands for the blue, type I Cu-binding site and for a putative type-II site were identified. The nirK gene was transferred to the mutant MK202 of P. stutzeri which lacks cytochrome cd 1 nitrite reductase due to a transposon Tn5 insertion in its structural gene, nirS. The heterologous enzyme was active in vitro and in vivo in this background and restored the mutationally interrupted denitrification pathway. Transfer of nirK to Escherichia coli resulted in an active nitrite reductase in vitro. Expression of the nirS gene from P. stutzeri in P. aureofaciens and E. coli led to nonfunctional gene products. Nitrite reductase activity of cell extract from either bacterium could be reconstituted by addition of heme d 1, indicating that both heterologous hosts synthesized a cytochrome cd 1 without the d 1-group.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00258141

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Prediction of the properties of model polymer solutions and blends (1994)

Ghonasgi, D. ; Chapman, Walter G.

Hoboken, NJ : Wiley-Blackwell

AIChE Journal 40 (1994), S. 878-887

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ISSN: 0001-1541

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology

Notes: In this work we present an extension of the statistical associating fluid theory (SAFT) developed for associating fluids by applying this extension to polymer solutions and blends. The polymer molecule is modeled as a flexible chain made of bonded spherical segments. These segments interact with the Lennard-Jones potential. The extension of SAFT is compared with molecular simulation results for polymer solutions and blends. Since the same force model is used in the simulation and theory, this comparison is a strong test of the assumptions made in deriving the theory. Results are presented for pure polymers of up to 50 segments long, polymer solutions of a polymer 20 segments long dissolved in its own monomer, and blends of polymers of 25 segments each. The theory produces results that are in better agreement with simulation results than the Flory-Huggins theory for the systems studied.

Additional Material: 9 Ill.