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Biomedical subjects

L Jaenicke

Publications and source records attributed to L Jaenicke.

At least 37 records · Page 2Linked to original sources
PubMed1987

Assay of reducing sugars in the nanomole range with 2,2'-bicinchoninate.

The photometric assay of reducing sugars with 2,2'-bicinchoninate was improved and its conditions were optimized. Optical density is linear between 1 and 25 nmol sugar/sample, and the assay is not affected by borate, phosphate, or other buffer anions. The molar extinction coefficients produced by the standard procedure with the 12 most common monosaccharides occurring in carbohydrates and conjugated glycocompounds are listed.

Indicators and Reagents↗
PubMed1986

Total synthesis of chain-length-uniform dolichyl phosphates and their fitness to accept hexoses in the enzymatic formation of lipoglycans.

Dolichols of defined uniform chain length (C35, C45, and C55) and geometry were prepared by total synthesis according to the following principle: (E,E)-Farnesol, activated as its 4-tolyl sulfone, is condensed with 8-chloroneryl benzyl ether, the sulfonyl group removed and the ether linkage cleaved by lithium/triethylamine. The resulting elongated prenol is converted again to its corresponding 4-toly/sulfone; at this stage isomers are removed by chromatography. After several cycles of this C10-elongation sequence the synthesis is completed in the same way but using 8-chlorocitronellyl benzyl ether as building block to introduce the saturated alpha-isoprene unit. The dolichols obtained were chemically phosphorylated (POCl3/Et3N). Both, the alcohols and their phosphate esters, are characterized spectroscopically. 1H- and 13C-NMR data are recorded for qualitative and stereochemical comparison with natural dolichols. The authentic dolichyl phosphates (Dol-7-P, Dol-9-P, and Dol-11-P) were assayed relative to the natural dolichyl phosphate mixture from pig liver as acceptors for transglycosylation from nucleoside diphosphate sugars (glucose, mannose) by standardized membrane vesicle preparations from plants (Volvox) and animals (liver). Even the shortest chain dolichyl 7-phosphate has full activity in this lipoglycan-forming reaction.

Chemical Phenomena↗
PubMed1985

Cyclic AMP as an intraspheroidal differentiation signal in Volvox carteri.

The action of the macromolecular inducer glycoprotein on sexual reproduction in the green alga Volvox carteri can be modified by altering the external (intraspheroidal) cAMP concentration. Direct proof for the presence of cAMP in the spheroids is given. Protein binding assay and HPLC-fluorimetric analysis independently demonstrate the existence of cAMP in the matrix, cells, and culture medium. Its concentration is higher in sexual cultures, pointing to a transmitting function in sex induction. The presence in the matrix of other members of a protein phosphorylation system suggests an induction-specific signal cascade in this plant.

Cell Differentiation↗
PubMed1984

Differentiation of algal chemoreceptors. A comparative receptor study with two seaweed pairs: Cutleria multifida/Syringoderma phinneyi and Desmarestia aculeata/Ectocarpus siliculosus (Phacophyceae).

Gamete encounter in the reproduction of brown algae is supported by lures produced by the female cells. These signals are low-molecular-mass, volatile, olefinic hydrocarbons. Specific receptors on the motile male gametes recognize the pheromones at threshold concentrations as low as 6.5 pmol/l. The pheromones are possibly bound by dispersion and dipolar interactions. Tight fitting has to compensate for these weak contact forces. This causes strong chiral discrimination (relative affinities to enantiomeric lures 1:100). Structurally related messengers with identical substitution patterns and overall space filling are mutually distinguished in several species by means of altered topologies in their receptor mould. Responses to systematically varied synthetic bis-alkenyl-cyclopentene pheromones showed that the sensors of Syringoderma and Cutleria androgametes consist of a mosaic of attachment sites individually adapted to specific structural elements in the messenger molecule. They may be permutated to afford optimal binding. An alternative strategy: distinct reading of electron density combined with variation of sensitivity, brings about 'fidelity' in signal transmission by the alkylated cycloheptadiene pheromones in two species of Desmarestia and Ectocarpus. Inhibition of chemotaxis by ectocarpene is observed in Ectocarpus males in the presence of desmarestene, the lure of Desmarestia, and related parapheromones. This indicates complex interactions between different species of algae sharing a common habitat, in their defense of living space.

Animals↗
PubMed1984

Chemical modification of hydroxynitrile lyase by selective reaction of an essential cysteine-SH group with alpha, beta-unsaturated propiophenones as pseudo-substrates.

3-Oxo-3-phenylpropyne and 3-oxo-3-phenylpropene were synthesized as active-site-directed irreversible inhibitors of the bitter almond hydroxynitrile lyase (EC 4.1.2.10), an FAD-protein. The substrate and competitors (e.g. benzoate) decrease the rate of the inhibitor-mediated deactivation of the enzyme. By excess addition of either one of the two inhibitors, the deactivation process is shown to be pseudo-first order. The reaction with equimolar amounts of 3-oxo-3-phenylpropyne with the enzyme is accompanied by a shift in the ultraviolet spectrum of the inhibitor, allowing direct measurement of the enzyme-inactivation process. The spectral change has second-order kinetics. Incubation with 3-oxo-3-[p-3H]phenylpropyne or 3-oxo-3-[1-14C]phenylpropene shows a one-to-one stoichiometry for the inhibitory-enzyme reaction. Dissociation of the 3-oxo-3[p-3H]phenylpropyne-inactivated holoenzyme with acid ammonium sulfate yields a labeled apoenzyme; the inhibitor does not react with free or enzyme-bound FAD. After boranate reduction and exhaustive hydrolysis of the 3-oxo-3-[1-14C]phenylpropene-inactivated enzyme, a labeled cysteine derivative was isolated which was identified by chromatographic and mass spectroscopic comparison with synthetic references as L-2-amino-4-thia-DL-7-hydroxy-7-phenylhepatanoic acid, the reduced, linear addition product of the inhibitor to a cysteine-SH group.

Affinity Labels↗
PubMed1984

Evidence for an incomplete dolichyl-phosphate pathway of lipoglycan formation in Volvox carteri f. nagariensis.

Crude membrane fractions from Volvox carteri in the presence of detergent and metal complexing agent catalyze the transfer of glucose from dolichyl phosphate glucose to branched dolichyl diphosphate chitobiosyl pentamannoside Dol-PP-(GlcNAc)2-(Man)5, a known intermediate of the lipid-mediated pathway of N-glycosylation of proteins, resulting in the formation of Dol-PP-(GlcNAc)2-(Man)5-(Glc)1. Under the various conditions tested, neither Dol-P-Man nor other known mannosyl donors of the nucleoside-activated or lipid-activated type can serve as donor molecules for the elongation of the lipid-linked heptasaccharide. On the other hand, calf liver microsomes in similar experiments mannosylated the heptasaccharide further with Dol-P-Man up to a nonamannoside, Dol-PP-(GlcNAc)2-(Man)9. A direct glucosylation of the acceptor, however, with Dol-P-Glc failed in this system. The (GlcNAc)2-(Man)5-(Glc)1, obtained after mild acid hydrolysis of the above glycolipid is not significantly split by an unspecific alpha-glucosidase from yeast. However, Volvox microsomes liberated most of the glucose indicating a specific glucosidase in the membranes of the alga. This enzyme does not act on (GlcNAc)2-(Man)9-(Glc)1, the usual protein-linked carbohydrate intermediate of trimming processes of N-glycosidic glycoproteins. The data on glycolipid formation let us postulate that in Volvox the normal N-glycosylation pathway differs from that found in higher plants and animals either by a lack of evolution or by mutation in the genes coding for the mannosyl transferases involved.

Cations↗
PubMed1983

Comparative receptor study in gamete chemotaxis of the seaweeds Ectocarpus siliculosus and Cutleria multifida. An approach to interspecific communication of algal gametes.

Gamete fusion in phaeophytes is initiated by olefinic hydrocarbons as messenger substances. They are secreted by the female gametes and act on male gametes or gametangia. The sensitivity thresholds of the androgametes of Ectocarpus siliculosus and Cutleria multifida, two brown algae of different evolutionary stages, for ectocarpene, which is produced by either species, were found to be 0.89 nmol/l and 8.9 nmol/l sea water, respectively. The molecular recognition mechanism is shown to be identical for these two species and probably also for most other phaeophytes. The pheromones involved are structurally related and sometimes resemble each other in their overall pi-electron distribution (e.g. ectocarpene and multifidene). Knowing the specific messenger, the typical response behaviour of each receptor involved, the pheromone productivity of the considered species as well as other biological parameters (phytogeographic distribution, the natural benthic habitat and times of fertilization), a method is presented to uncover possible interspecific cross-reactions of such algal communication systems as a 'chemical warfare' device in their fight for living space.

Animals↗
PubMed1983

Synthesis and characterization of lipid-linked mannosyl oligosaccharides in Volvox carteri f. nagariensis.

Particulate membrane fractions from Volvox carteri catalyze the transfer of mannose from GDP-mannose to dolichyl diphosphate-[14C]chitobiose to form lipid-linked oligosaccharides up to a dolichyl diphosphate-chitobiose-(mannose)5 structure. Mannosylation of the chitobiosyl lipid requires divalent cations and detergents as solubilizing agents. Depending on the nature of the detergent, the oligosaccharide pattern differs markedly: With deoxycholate or the zwitterionic detergent 3-14 a lipid-linked trisaccharide accumulates. The nonionic Triton X-100, however, gives rise to a spectrum of compounds up to a heptasaccharide. Enzyme digestion of the tri- and pentasaccharide structure, obtained after mild acid hydrolysis of the corresponding [14C]glycolipids, revealed that the first mannose is bound via a beta-glycosidic linkage to the chitobiosyl core, whereas the outer mannose residues are linked as alpha-mannosides. Our studies indicate that, in agreement with recent findings in other organisms, the innermost alpha-mannosidic residues are donated directly from GDP-mannose. The structure of oligosaccharides synthesized by Volvox membranes is thus consistent with results from other eucaryotic species, suggesting a common pathway of N-glycosylation of glycoproteins.

Chemical Phenomena↗
PubMed1982

Binding-mechanism and sensitivity in gamete chemotaxis of the phaeophyte Cutleria multifida.

Female gametes of the marine brown alga Cutleria multifida discharge multifidene into the water to attract the swimming males. The physicochemical principle of interaction between semiochemical and membrane receptor site is seen in mutual but complementary induced dipoles. Halogenated derivatives of multifidene with intact overall structure and stereochemistry but altered electronic properties were synthesized and assayed as lures. A direct correlation was observed between increasing polarizability and biological activity, thus proving the proposed mechanism. The low threshold concentration of this communication system (4 X 10(9) molecules/ml), together with a detailed knowledge of the gamete's architecture, swimming velocity and stimulus response time, indicates that very few, may be even single, molecules are able to trigger the sensomotoric chain. The rigidity of the natural signal molecule was recognized as an important element in inducing conformational fitting in the ligand/receptor complex.

Binding Sites↗
PubMed1977

[Determination of indolalkylamines after selective derivatisation (author's transl)].

The 1N-TMS-omegan-TFA-derivatives of indolalkylamines are suitable for estimation by combined gas chromatography and mass spectrometry for two reasons, viz. (1) Under electron impact charge stabilisation at the indole nucleus is favoured, so structure-specific ions form the base peak. For unsubstituted indoles m/e values of 202 are found and for hydroxyl-substituted indoles m/e values of 290. (2) The calibration curves of the derivatives are linear, even in the femtomole range. The 1N-TMS-omegan-derivatives can easily be obtained by trimethylsilylation with N-methyl-N-trimethylsilyltrifluoroacetamide containing catalytic amounts of N-trimethylsilylimidazole followed by acylation with N-methyl bis(trifluoroacetamide). The serotonin concentrations in different rat tissues are determined by this method of selective omegaN-trifluoroacylation-1N-trimethylsilylation and compared with the values obtained by pertrimethylsilylation.

Animals↗
PubMed1977

Glutamine synthetase from pig brain: binding of adenosine triphosphate.

Glutamine synthetase was purified to homogeneity from fresh brain homogenates by a procedure that makes use of the affinity of this ATP requiring ligase to Cibacron 3G-A Blue-Sephadex G-75. It is shown that the interaction of pig brain enzyme with the dye does not concern the active centre but a non-catalytic although specific ATP binding site. Both sides contain a cysteine residue which may react with N-ethylmaleimide. The unprotected succinimidated enzyme is inactive, and aggregates. ATP alone protects only against aggregation, not against inactivation; the ATP/Mg2 complex also hinders inactivation. A tryptic heptadecapeptide isolated from the derivatized enzyme representing the carboxy terminal seems to belong to the active centre; its amino acid sequence was partially determined.

Adenosine Triphosphate↗