Zeitschrift fur Naturforschung. Section C, Biosciences最新文献

Rabbit antibodies against small peptides may be composed by subpopulations recognizing different epitopes made likely by few amino acids. This explains the frequent crossreactivity of antipeptide antibodies with unrelated peptides. A suitable use of immunoadsorbents is suggested to obtain truly specific antibodies able to react with restricted amino acid sequences.

Cultures of vitamin D-deficient chick soleus muscle and 12 day-old chick embryo myoblasts were used to characterize the effects of 1,25-dihydroxy-vitamin D3 and 25-hydroxy-vitamin D3 on muscle cell Ca metabolism. Physiological amounts of both sterols increased the rate and extent of 45Ca uptake by cultures. However, 1,25(OH)2D3 was significantly more effective than 25 OHD3. The greater potency of 1,25(OH)2D3 to increase Ca uptake could be shown after various treatment intervals of cultures and using a wide concentration range of both derivatives. Information about Ca pools affected by vitamin D3 metabolites was obtained through kinetic analysis of Ca efflux in cultured myoblasts. Cytoplasmic and mitochondria Ca pools were identified on the basis of their half-times of desaturation and by selective inhibition of plasma membrane and mitochondrial Ca transport with LaCl3 and Ruthenium Red, respectively. The data suggests that 1,25(OH)2D3 acts on muscle cellular Ca by increasing Ca efflux and influx through mitochondrial and plasma membranes whereas the predominant effect of 25 OHD3 is to increase Ca influx into mitochondria.

An enzymatic assay system for nitrate employing the membrane-bound nitrate reductase (EC 1.7.99.4) of E. coli is described. Contrary to previous enzymatic assay systems, the present method is a kinetic one, i.e. the substrate, nitrate, is assayed by measuring the reaction rate of the nitrate reductase-catalyzed reaction. Based on the observation that the nitrate reductase-catalyzed reaction obeys pseudo-first order kinetics, a test system is described allowing the assay of nitrate at a concentration as low as 1 ppm. The relatively high Michaelis-Menten constant for nitrate (0.3 mM) of the E. coli nitrate reductase favours nitrate assay by the kinetic method.

Four extracellular glycolipids produced under growth-limiting conditions were isolated from the culture broth of Pseudomonas spec. DSM 2874. After purification by column and thick-layer chromatography they were identified as anionic rhamnolipids. 1H and 13C-NMR studies showed that two of these, beta(beta(2-O-alpha-L-rhamnopyranosyloxy)decanoyl)decanoic acid and beta(beta(2-O-alpha-L-rhamnopyranosyl-alpha-L-rhamnopyranosylox y)decanoyloxy) decanoic acid, were identical with compounds described previously, while the other more hydrophilic compounds, beta(2-O-alpha-L-rhamnopyranosyloxy)decanoic acid and beta(2-O-alpha-L-rhamnopyranosyl-alpha-L-rhamnopyranosyloxy) decanoic acid, were new compounds. Surface and interfacial activity of the organic crude extract and of the purified components were determined in different aqueous solutions. The pH-dependence of surface and interfacial properties of the two previously described rhamnolipids (4, 20, 23) were examined in Teorell-Stenhagen-buffer (supplemented with 10% NaCl) at pH 3.0 and pH 9.0. All rhamnolipids reduced the surface-tension from 72 to about 30 mN/m and the interfacial-tension from 42 to about 1 mN/m. The critical micelle concentrations were of the order of 5 to 200 mg/l depending on the structure of the molecule.

Extraction of fresh sporophores of the fungus Agaricus xanthodermus yields 4,4'-dihydroxy-azobenzene, phenol, p-quinol, and 4,4'-dihydroxybiphenyl. This is the first report of an azo compound arising endogenously in nature, while phenol, p-quinol and 4,4'-dihydroxybiphenyl have not previously been isolated from higher fungi. Phenol is present in fruitbodies in sufficiently high concentration to account for the toxicity of A. xanthodermus.

The affinity of the sarcoplasmic reticulum transport ATPase for calcium and ATP is not affected by lipid deprivation while vanadate binding is completely abolished. Lipid substitution restores vanadate binding as well as the vanadate induced disappearance of the enzyme's high affinity calcium and nucleotide binding sites. Nucleotide binding is simultaneously restored with the displacement of vanadate from the enzyme following the occupation of its low affinity calcium binding sites.

[4-(3-Bromoacetylpyridinio)-butyl]adenosine pyrophosphate as a structural analog of NAD+ reacts covalently with the sulfhydryl groups of thiopropyl agarose. 10-20 mumol can be bound to 1 ml gel. Stabilization of the insoluble coenzyme is attained by treatment with sodium boro hydride (NaBH4). This complex when applied to column chromatography, allows the separation of various dehydrogenases as a result of their different complex stability coefficients. Alcohol dehydrogenase from liver, lactate dehydrogenase, and adenylate kinase, which all bind to the ADP-analog residues of the gel matrix, can thus be separated by different salt gradients. Alcohol dehydrogenase from yeast, however, does not form a complex and can easily be eluted from the column with phosphate buffer. Glyceraldehyde-3 phosphate and aldehyde dehydrogenases can be eluted by the addition of NAD+ or NADH to the buffer. The uncharged 1,4-dihydropyridine ring of the reduced coenzyme produces a more stable complex with the dehydrogenases than the oxidized form.

Yield of streptolysin S (SLS) in streptococcal culture was considerably reduced by procaine, dibucaine, atropine or chlorpromazine at concentrations which scarcely affected production of an extracellular nuclease as well as the bacterial growth. Cerulenin was also inhibitory to SLS formation, but its effect was more pronounced on the nuclease production. By aerobiosis, amount of SLS produced into culture supernatant was increased significantly, whereas yield of the nuclease was rather unaffected.

Calf thymus histone octamer complexes were irradiated in the native state in N2O-saturated dilute aqueous solution (0.5 g/l, pH 9, [NaClO4] = 1 -4 mol/l) with 50 or 100 ns pulses of 16 MeV electrons or 60Co-gamma-rays. Time resolved light scattering measurements and optical absorption measurements yielded the following: the octamers underwent a volume contraction due to intra-complex-crosslinking induced by the attack of OH-radicals. Crosslinking proceeded to a certain extent via 2,2'-biphenol coupling as inferred from product analyses.

The production of platinated derivatives of nucleic acid bases resulting from the reaction of cis and trans DDP with DNA and chromatin was studied. Bifunctional complex of guanine appeared to be the major product of the interaction of cis isomer with both DNA and chromatin, although other bifunctional adducts of A-Pt-G and A-Pt-A were also isolated. The main product of the interaction of trans DDP with DNA was a monofunctional adduct of guanine. Small amounts of the bifunctional complexes were also isolated. When ssDNA was incubated with trans DDP more bifunctional complexes appeared, what suggests that geometric constrains of double helix prevent formation of these complexes. Trans isomer reacts more easily with chromosomal proteins than cis DDP does. Therefore after the reaction of trans DDP with chromatin less platination occurs on DNA moieties.