Search PubMed⌕ Search

Biomedical subjects

K Biemann

Publications and source records attributed to K Biemann.

At least 127 records · Page 7Linked to original sources
PubMed1976

Methylation artifacts in the gas chromatography of serum extracts. Competitive suppression with trimethyl-d9 anilinium hydroxide.

In the course of the identification of drugs in body fluids by gas chromatography-mass spectrometry we have observed the appearance of N-methyl derivatives of certain compounds such as phenobarbital and diphenylhydantoin, especially in extracts of serum. With the aid of deuterium labelled phenobarbital it could, however, be shown that the N-methyl derivatives are not endogenous metabolites but artifacts generated upon injection of the serum extract into the gas chromatograph. Conversely, derivatization with trimethyl-d9 anilinium hydroxide (TMAH-d9) demonstrated the absence of any undeuterated methyl derivative and this reagent should be useful for the detection of endogenous N-methyl derivative which would, of course, remain undetected when using unlabelled TMAH in the course of the conventional methylation technique. There are good indications that lecithin is the methylating agent in serum responsible for the formation of these artifacts.

Aniline Compounds↗
PubMed1976

Metabolites of phencyclidine.

The results of the animal experiment demonstrate that oxidative hydroxylation is the major mode of metabolism of phencyclidine. It is evident that this process takes place in all three rings of the molecule. Hydroxylation of the piperidyl moiety probably also accounts for the formation of the N-dealkylated metabolites. Metabolism of phencyclidine in humans appears, at least in part, to be similar to that in the rat. Hydroxylation is still the principal mode in the case of humans though of a lesser extent. Metabolites hydroxylated in the phenyl moiety as well as dihydroxy derivatives of phencyclidine have so far not been observed in humans. Furthermore, most of the monohydroxy metabolites exist as conjugates in the human urine. It should also be pointed out that no metabolites have yet been detected in human blood samples.

Animals↗
PubMed1975

The amino acid sequence of a carboxypeptidase inhibitor from potatoes.

The carboxypeptidase inhibitor from Russet Burbank potatoes (C. A. Ryan et al. (1974b), J. Biol. Chem 249, 5495) is a mixture of approximately equal amounts of two polypeptide chains containing 38 and 39 amino acid residues, respectively. The chains differ in their amino terminal sequence only, one beginning with smaller than Glu-His-Ala ... and the other with smaller than Glu-Gln-His-Ala ..... Specific cleavage procedures utilized in determining the complete amino acid sequence of the inhibitor included acid cleavage of the aspartyl-proline bond and tryptic and chymotryptic digestion. Mass spectrometry, automatic Edman degradation, and subtractive Edman degradation were employed in sequencing the resulting peptide fragments.

Amino Acid Sequence↗
PubMed1973

The structure of novel C35 pentacyclic terpenes from Acetobacter xylinum.

A novel C(35) terpene and its monounsaturated analogue were isolated from cultures of Acetobacter xylinum, together with traces of their C(36) homologues. These substances were found to be hopane derivatives substituted by a five-carbon chain bearing four vicinal hydroxyl groups. For the parent hydrocarbon the term bacteriohopane is proposed. The elucidation of the structures utilized high-resolution mass spectrometry of the terpenes, degradation to C(32) hydrocarbons and detailed mass-spectrometric comparison of these with C(32) hydrocarbons synthesized from known pentacyclic triterpenes. High-resolution mass-spectral data of the terpenes are presented. N.m.r. data are in agreement with the proposed structures, which are further supported by the isolation from the same organism of 22-hydroxyhopane and derivative hopene(s).

Chromatography, Gas↗
PubMed1973

Induction of orientation of bacterial cellulose microfibrils by a novel terpenoid from Acetobacter xylinum.

1. The bacterium Acetobacter xylinum produces extracellular cellulose microfibrils that form a pellicle in the medium enmeshing the bacterial cells. These microfibrils may show some localized alignment, which can be seen as birefringence when the culture is viewed between crossed Polaroid sheets. 2. An increase in birefringence can be induced by the addition of small amounts of certain classes of lipids, particularly sterols, to the cultures. 3. A crude lipid extract from Acetobacter cells induced greatly increased birefringence when added to fresh cultures of this organism. 4. When the bacterial lipids were fractionated, most of the activity was recovered in a complex, polar lipid. The lipid is secreted into the medium during growth and is unstable. The non-saponifiable portion of this lipid is shown to be a 1:1 mixture of a saturated and a monounsaturated C(35) tetrahydroxy terpene with a hopane ring system in the accompanying paper by Förster et al. (1973). The saturated molecule is referred to as tetrahydroxybacteriohopane. 5. Tetrahydroxybacteriohopane is itself capable of inducing birefringence in cultures as is 22-hydroxyhopane, which was also isolated from the non-saponifiable fraction of the total lipids. 6. The mechanism of induction of birefringence (orientation of microfibrils) is not known. This is unlikely to be a specific effect, since all the above compounds are active (intact lipid, tetrahydroxybacteriohopane, 22-hydroxyhopane), as are other classes of lipid. It is suggested, however, that a common mechanism may be involved and that similar compounds may be concerned with control of microfibril alignment in the cells of higher plants.

Alcohols↗
PubMed1972

Water pollution: organic compounds in the Charles River, Boston.

The major lipophilic organic compounds present in water collected during November and December 1971 from the Charles River Basin (Boston) are as follows: normal alkanes (C(15) to C(31)), alkyl naphthalenes, alkyl anthracenes or phenanthrenes, pyrene, fluoranthene, dibutyl phthalate, and di(2-ethylhexyl) phthalate. The concentration of the naphthalenes (determined by liquid chromatography) correlates with the effective storm-water runoff content of the river. These data suggest a multiplicity of sources ranging from indigenous biological materials to automobile exhaust condensate.

Alkanes↗
PubMed1969

Phenethyl alcohol and tryptophol: autoantibiotics produced by the fungus Candida albicans.

Two autoantibiotics produced by the fungus Candida albicans have been identified, with the aid of mass spectrometry, as 2-phenylethanol and 3-beta-hydroxyethylindole. The cyclodipeptides, cyclo(proline-leucine) and cyclo(proline-phenylalanine) were also isolated from cultures of Candida albicans, but did not inhibit the growth of the fungus.

Anti-Bacterial Agents↗