PubMed Health⌕ Search

Biomedical subjects

A Kiener

Publications and source records attributed to A Kiener.

16 recordsLinked to original sources
PubMed2004

Polycarnitine--a new biomaterial.

The natural product L-carnitine is--due to its biotechnological accessibility and specific properties--on the way to becoming an attractive biobased bulk product. L-carnitine is a natural betaine with vitamin properties. Carnitine is an essential part of the fatty acid metabolism of human beings and animals. Carnitine was first isolated in 1905 from meat extract and important recent developments include the biosyntheses of L-carnitine from L-lysine or gamma-butyrobetaine. Our synthesis routes are designed to maintain the primary structure and specific properties of carnitine, such as hydrophilicity and "stiffening" effects for polymeric structures and applications. L-carnitine is converted via lactonization or olefinization into polymerizable basic molecules. The properties and the applications of carnitine polymers are described.

Biotechnology↗
PubMed2001

Industrial biocatalysis today and tomorrow.

The use of biocatalysis for industrial synthetic chemistry is on the verge of significant growth. Biocatalytic processes can now be carried out in organic solvents as well as aqueous environments, so that apolar organic compounds as well as water-soluble compounds can be modified selectively and efficiently with enzymes and biocatalytically active cells. As the use of biocatalysis for industrial chemical synthesis becomes easier, several chemical companies have begun to increase significantly the number and sophistication of the biocatalytic processes used in their synthesis operations.

Catalysis↗
PubMed2000

Novel regioselective hydroxylations of pyridine carboxylic acids at position C2 and pyrazine carboxylic acids at position C3.

We have previously described the isolation of the new bacterial species, Ralstonia/Burkholderia sp. strain DSM 6920, which grows with 6-methylnicotinate and regioselectively hydroxylates this substrate in the C2 position by the action of 6-methylnicotinate-2-oxidoreductase to yield 2-hydroxy-6-methylnicotinate (Tinschert et al. 1997). In the present study we show that this enzymatic activity can be used for the preparation of a series of hydroxylated heterocyclic carboxylic acid derivatives. The following products were obtained from the unhydroxylated educts by biotransformation using resting cells: 2-hydroxynicotinic acid, 2-hydroxy-6-methylnicotinic acid, 2-hydroxy-6-chloronicotinic acid, 2-hydroxy-5,6-dichloronicotinic acid, 3-hydroxypyrazine-2-carboxylic acid, 3-hydroxy-5-methylpyrazine-2-carboxylic acid and 3-hydroxy-5-chloropyrazine-2-carboxylic acid. Thus the respective educts were all regioselectively mono-hydroxylated at the carbon atom between the ring-nitrogen and the ring-carbon atom carrying the carboxyl group. In contrast to its relatively broad biotransformation abilities, the strain shows a limited heterocyclic nutritional spectrum. It could grow only with three of the seven transformed educts: 6-methylnicotinate, 2-hydroxy-6-methylnicotinate and 5-methylpyrazine-2-carboxylate. 2-Hydroxynicotinate, 2-hydroxy-6-chloronicotinate, 2-hydroxy-5,6-dichloronicotinate, 3-hydroxypyrazine-2-carboxylate and 3-hydroxy-5-chloropyrazine-2-carboxylate were not degraded by the strain. Therefore, unlike 6-methylnicotinate-2-oxidoreductase, which has a broad substrate spectrum, the second enzyme of the 6-methylnicotinate pathway seems to have a much more limited substrate range. Among 28 aromatic heterocyclic compounds tested as the sole source of carbon and energy, only pyridine-2,5-dicarboxylate was found as a further growth substrate, and this was degraded by a pathway which did not involve 6-methylnicotinate-2-oxidoreductase. To the best of our knowledge the microbial production of 2-hydroxy-6-chloronicotinic acid, 2-hydroxy-5,6-dichloronicotinic acid and 3-hydroxy-5-methylpyrazine-2-carboxylic acid have not been reported before. Strain DSM 6920 is so far the only known strain which allows the microbial production of both these compounds and 3-hydroxypyrazine-2-carboxylic acid and 3-hydroxy-5-chloroypyrazine-2-carboxylic acid.

Biotransformation↗
PubMed1997

Isolation of new 6-methylnicotinic-acid-degrading bacteria, one of which catalyses the regioselective hydroxylation of nicotinic acid at position C2.

2-Hydroxynicotinic acid is an important building block for herbicides and pharmaceuticals. Enrichment strategies to increase the chances of finding microorganisms capable of hydroxylating at the C2 position and to avoid the degradation of nicotinic acid via the usual intermediate, 6-hydroxynicotinic acid, were used. Three bacterial strains (Mena 23/3-3c, Mena 25/4-1, and Mena 25/ 4-3) were isolated from enrichment cultures with 6-methylnicotinic acid as the sole source of carbon and energy. Partial characterization of these strains indicated that they represent new bacterial species. All three strains completely degraded 6-methylnicotinic acid, and evidence is presented that the first step in the degradation pathway of strain Mena 23/3-3c is hydroxylation at the C2 position. Resting cells of this strain grown on 6-methylnicotinic acid also hydroxylated nicotinic acid at the C2 position, but did not further degrade the product. Strain Mena 23/ 3-3c showed the highest degree of 16S rRNA sequence similarity to members of the genera Ralstonia and Burkholderia.

Bacillus↗
PubMed1992

Scanning force microscopy studies of the S-layers from Bacillus coagulans E38-66, Bacillus sphaericus CCM2177 and of an antibody binding process.

In many prokaryotic cells (eubacteria and archaebacteria) the outermost cell envelope component is composed of a regularly structured protein surface layer (S-layer). The two-dimensional S-layer from Bacillus coagulans E38-66 and Bacillus sphaericus CCM2177 has been investigated by SFM at molecular resolution under physiological conditions (i.e., in buffer solution). We find the E38-66 S-layer lattice to be oblique with lattice parameters of a = 9-10 nm, b = 7-8 nm and gamma = 80 degrees -90 degrees (E38-66). The CCM2177 lattice is square with a = 12-14 nm, in good agreement with TEM data. We have used the unique possibility of the SFM to study the kinematics of biological processes and have performed experiments on the adhesion of polyclonal antibodies to the recrystallized E38-66 protein layer on a time scale of about two to ten seconds per image frame. This represents a first step in directly visualizing molecular recognition reactions.

Antibodies, Bacterial↗
PubMed1990

Functional expression of 8-hydroxy-5-deazaflavin-dependent DNA photolyase from Anacystis nidulans in Streptomyces coelicolor.

The gene encoding Anacystis nidulans 5-deazaflavin-dependent photolyase (phr) was inserted into the Streptomyces vector pIJ385 to form a transcriptional fusion with the neomycin resistance (aph) gene. The resulting plasmid, pANPL, was introduced into Streptomyces coelicolor, a host which exhibits no detectable photolyase activity and provides 5-deazaflavins. Transformants expressed functional photolyase and could be cultured at much higher cell densities than A. nidulans. A two-step affinity protocol was used to purify photolyase to homogeneity. High-pressure liquid chromatographic analysis established the presence of 5-deazaflavin cofactors in the enzyme, showing that this expression system allows heterologous production of 5-deazaflavin-class photolyases.

Amino Acid Sequence↗
PubMed1990

[Thoracic drainage at the accident site].

The helicopter medical team of the Basel University Hospital treated and evacuated 710 patients in 1987/88. 484 were trauma patients (68.2%) and the intensive medical care began on the accident scene in 56% of the cases. We treated 90 thoracic injuries. 58.9% of these patients needed a chest tube which was directly inserted at the emergency place in 41.4% of the cases. An endotracheal intubation was necessary for 83.8% of the patients with in-field insertion of a chest tube and for 33.9% of other injured persons. No iatrogenic complications were observed. The clinical follow-up showed less complications for infield treated patients. We conclude that in-field insertion of chest tubes, if correctly performed, is a safe procedure contributing to diminish the lethality and the morbidity of trauma patients.

Accidents, Traffic↗
PubMed1990

[Traumatology and emergency medicine: helicopter evacuation in the Basel area].

999 patients were treated and evacuated by medical helicopter in the region of Basel between 1986 and 1988. 687 were trauma patients (70.5%) and among them 53.9% were directly treated on the accident scene. Mortality during the stabilization prior to transport (2.6%) and during transport (0.3%) was low. The presence of a physician in the helicopter allows fast and intensive in-field care. All life-saving procedures like endotracheal tubes (36.3%), closed intercostal drainage (7.4% of trauma patients) and cardiovascular reanimation (1.9), even hemostasis, or fixation of fractures are performed. Early in-field intensive care by medical helicopter decreases lethality and mortality and must be recommended by severe trauma.

Aircraft↗
PubMed1990

[Helicopter emergency medical system in the Basel region].

Between 1986 and 1988, 999 patients were treated on the emergency scene, then transported with the rescue-helicopter in the Basle area. 687 were victims of a trauma (70.5%) and 287 patients were suffering from an acute internal medicine disease. We performed in-field therapy on the accident scene itself in 53.9% of all the cases. According to our scoring system the presence of a physician was absolutely necessary in 56% of all the cases. Air rescue by helicopter allows fast transportation of patients and immediate high quality intensive care. The low mortality rate during treatment before transport (2.6%) and during the transport itself (0.3%) shows that early beginning of medical treatment on the accident scene is connected to better survival chances.

Accidents, Traffic↗
PubMed1989

Purification and properties of Methanobacterium thermoautotrophicum DNA photolyase.

We have purified DNA photolyase from the autotrophic anaerobic archaebacterium Methanobacterium thermoautotrophicum to near homogeneity by a two-column affinity chromatography. The purified enzyme has an Mr = 60,000 and shows near UV absorption peak at 440 nm and a fluorescence emission maximum at 462 nm indicating that it contains 8-hydroxy-5-deazaflavin (coenzyme F420) as an intrinsic chromophore. The photolyase binds with high specificity to thymine dimer in DNA with an equilibrium binding constant, KA = 1.4 x 10(9) M-1, and a dissociation rate constant, koff = 1.4 x 10(-4) s-1 (t1/2 = 43 min). Despite 6-fold higher affinity compared to the folate-containing Escherichia coli photolyase the two enzymes apparently contact the same phosphates around the thymine dimer: the phosphate immediately 5' and the three phosphates immediately 3' to the dimer on the damaged strand and the phosphate across from the dimer in the minor groove on the complementary strand. The absolute action spectrum of the Methanobacterium photolyase in the 400-500-nm region closely matches the absorption of the enzyme-bound F420. The quantum yield (phi) over this region is constant and is approximately 0.2. The value is measurably smaller than the quantum yields reported for other DNA photolyases.

Amino Acid Sequence↗
PubMed1988

Cloning and characterization of a photolyase gene from the cyanobacterium Anacystis nidulans.

A 2 kb fragment was isolated from an Anacystis nidulans genomic DNA library by hybridization with synthetic oligonucleotide probes derived from the N-terminal amino acid sequence of Anacystis photolyase. This fragment contains a 1452 bp-long open reading frame encoding a polypeptide of 484 amino acids (Mr 54475). Antibodies raised against purified Anacystis photolyase reacted with extracts of cells harboring fused genes between lacZ of Escherichia coli and this gene. A 40.7% similarity was found between the deduced amino acid sequences of Anacystis and E. coli photolyases, notwithstanding the difference in chromophore structure.

Amino Acid Sequence↗
PubMed1988

Reversible conversion of coenzyme F420 to the 8-OH-AMP and 8-OH-GMP esters, F390-A and F390-G, on oxygen exposure and reestablishment of anaerobiosis in Methanobacterium thermoautotrophicum.

Intracellular levels of F390 (AMP and GMP adducts of the 5-deazaflavin cofactor F420) in Methanobacterium thermoautotrophicum were analysed after gasing fermenter cultures with several consecutive cycles of substrate gas and gas mixtures containing 5% oxygen. No F390 was detected in growing cells, hydrogen starved cells and CO2 starved cells prior to O2 contamination. Also, no F390 was found in hydrogen depleted cells after O2 treatment. Exposure of exponentially growing cells and CO2 starved cells to oxygen lead to the formation of F390 species; the increase in the detected amount of F390 was coupled to a decrease of the F420 level. As soon as anaerobiosis was reestablished F390 cofactors were degraded and growth proceeded. Independent of the physiological condition of Methanobacterium thermoautotrophicum methanopterin was formed upon O2 exposure. After normal growth conditions were restored the level of detected methanopterin decreased again.

Anaerobiosis↗
PubMed1987

Purification and use of Methanobacterium wolfei pseudomurein endopeptidase for lysis of Methanobacterium thermoautotrophicum.

The pseudomurein-degrading enzyme from autolysates of Methanobacterium wolfei was purified approximately 500-fold to electrophoretic homogeneity by ion-exchange chromatography under anaerobic conditions. Analysis of the soluble cell wall fragments produced by the pure enzyme from a cell wall preparation of M. thermoautotrophicum indicated that it is a peptidase hydrolyzing the epsilon-Ala-Lys bond of pseudomurein. A partially purified preparation of pseudomurein endopeptidase was free of nuclease activity and thus proved useful for the preparation in high yields of undegraded chromosomal and plasmid DNA from M. thermoautotrophicum. The partially purified enzyme was also used for the preparation of protoplasts, which were stabilized by 0.8 M sucrose. Under growth conditions the protoplasts produced methane and increased up to 100-fold in size, but failed to regenerate a cell wall.

Endopeptidases↗
PubMed1983

A plasmid in the archaebacterium Methanobacterium thermoautotrophicum.

The archaebacterium Methanobacterium thermoautotrophicum Marburg (DSM 2133) was found to contain a plasmid (pME2001) in covalently closed circular form. It was isolated by CsCl gradient centrifugation of total DNA in the presence of ethidium bromide. Multimers up to the hexamer were observed upon agarose gel electrophoresis and electron microscopy of a purified plasmid preparation. A restriction map was constructed. The length of plasmid pME2001 was determined to be approximately 4,500 bp. Southern hybridization of plasmid DNA to DNA extracted from Methanobacterium thermoautotrophicum delta H (DSM1053) revealed the presence of a plasmid with homologous sequences in the delta H strain.

DNA Restriction Enzymes↗