Neutronenaktivierungsanalytische Bestimmung des Chromgehaltes von Laboratoriumskaninchen-Skelettmuskel

Zusammenfassung Als Beitrag zur Ermittlung der richtigen Werte der Chromgehalte von menschlichen und tierischen Geweben und Körperflüssigkeiten wurde der Chromgehalt von Laboratoriumskaninchen-Skelettmuskel neutronenaktivierungsanalytisch bestimmt. Bisherige Angaben anderer Autoren: <7,1–121 ng/g. Die Verbesserung einer in der Literatur angegebenen ⁵¹Cr-Abtrennung durch Chromylchloriddestillation und die erforderlichen Maßnahmen zur Minimierung des Chromblindwertes werden beschrieben. Dessen Hauptanteil wird durch die Restverunreinigung der Bestrahlungsampullen-Oberfläche mit Chrom bedingt und beträgt 0,049 ng Cr (ohne Gefriertrocknung) bzw. 0.12 ng Cr (mit Gefriertrocknung). Analysen von Standardreferenzmaterialien (SRM) ergaben Chromgehaltswerte, die bei NBS-Citrus Leaves mit dem Zertifikatswert, bei IAEA animal muscle (H-4) mit dem neuesten Literaturwert von 9,2±2,5 ng/g übereinstimmen. Im Falle von NBS-Orchard Leaves erwies sich, daß dieses SRM für die Überprüfung der Methode ungeeignet ist. In Analysen von Oberschenkelmuskel-Proben von Bastardkaninchen resultierten Chromgehalte von 6,2–22,9 ng/g (bezogen auf Frischgewicht). Aus dem Vergleich dieser Daten mit dem früher gefundenen Wert von 1,2 ng/g, dem Literaturwert <7,1 ng/g und dem auf Frischgewicht berechneten H-4-Wert von 2,5 ng/g folgt, daß die Chromgehalte von Säugetier-Skelettmuskel innerhalb eines breiten Bereiches liegen dürften, auch die von Muskel einer Subspecies.

---

Determination of the chromium content of laboratory rabbit skeletal muscles by neutron activation analysis

Summary The accurate values of the chromium contents of human and mammalian tissues and body fluids and appropriate procedures for their determination are still a matter of discussion. In this connexion, the chromium content of skeletal muscle of laboratory rabbits has been determined using neutron activation analysis. Data hitherto published by other authors: <7.1–121 ng/g. The procedure for separation of ⁵¹Cr by distillation of chromium oxychloride, described in the literature, has been improved. The arrangements necessary to minimize the chromium blank values are described. The main component of this blank is caused by the residual chromium contamination of the surface of the sample vial; typical values of this component are 0.049 ng Cr (without lyophilization) and 0.12 ng Cr (with lyophilization). The analyses of standard reference materials (SRM) yielded values of the chromium contents that are in agreement (i) with the certified value in the case of NBS Citrus Leaves, and (ii) with the latest published value of 9.2±2.5 ng/g in the case of IAEA animals muscle (H-4). NBS Orchard Leaves was found not to be an appropriate SRM for testing the method. In analyses of samples of thigh muscle of bastard rabbits chromium contents of 6.2–22.9 ng/g (fresh weight basis) were obtained. Comparison of these data with a previously found value of 1.2 ng/g, the literature value <7.1 ng/g and the value 2.5 ng/g for H-4 calculated on fresh weight basis indicated that the chromium contents of mammalian skeletal muscle might lie in a broad range, even for a subspecies.

---

---

Herrn Prof. Dr. K. H. Lieser zum 65. Geburtstag gewidmet     

Null Sequences in Coechelon Spaces

Rotundity of finite -dimensional Orlicz spaces l^?_n equipped with the Luxemburg norm is considered. It is proved that criteria for rotundity of l^?_nfor n ≥ 3 does not depend on n and are the same as the criteria for rotundity of the inhite-dimensional subspace h^? of an Orlicz sequence spacel^?. Criteria for rotundity of l^?₂ are different. Next, criteria for exposed points, (H)- points, strongly exposed points and LUR- points of the unit sphere of l^? and of its subspace h^? are given.     

A simple molecule with a complex crystal structure: interplay of 31P solid-state NMR spectroscopy and single-crystal x-ray diffraction in the structure determination of a ruthenium diphosphine diamine complex

A comprehensive 31P solid-state NMR study of Ru(eta1-Ph2PCH2CH2OCH3)2(eta2-en)Cl2 (en = ethylenediamine) (1), by 1D (contact time variation, inversion-recovery, SPARTAN) and 2D techniques (homonuclear J-resolved, SECSY) indicated that the crystal structure of 1 should be complex. The single-crystal x-ray structure determination confirmed the presence of eight independent molecules in the asymmetric unit, with 31P isotropic chemical shifts in the range 27.3-40.1 ppm, while the spans of the phosphorus chemical shift tensors are of the order of 170 ppm. Based on unique structural features and NMR data, one molecule has been tentatively assigned.     

Stability of phospholipid vesicles studied by asymmetrical flow field-flow fractionation and capillary electrophoresis

The stability of zwitterionic phosphatidylcholine vesicles in the presence of 20 mol% phosphatidyl serine (PS), phosphatidic acid (PA), phosphatidyl inositol (PI), and diacylphosphatidyl glycerol (PG) phospholipid vesicles, and cholesterol or calcium chloride was investigated by asymmetrical flow field-flow fractionation (AsFlFFF). Large unilamellar vesicles (LUV, diameter 100 nm) prepared by extrusion at 25 °C were used. Phospholipid vesicles (liposomes) were stored at +4 and −18 °C over an extended period of time. Extruded egg yolk phosphatidylcholine (EPC) particle diameters at peak maximum and mean measured by AsFlFFF were 101 ± 3 nm and 122 ± 5 nm, respectively. No significant change in diameter was observed after storage at +4 °C for about 5 months. When the storage period was extended to about 8 months (250 days) larger destabilized aggregates were formed (172 and 215 nm at peak maximum and mean diameters, respectively). When EPC was stored at −18 °C, large particles with diameters of 700–800 nm were formed as a result of dehydration, aggregation, and fusion processes. In the presence of calcium chloride, EPC alone did not form large aggregates. Addition of 20 mol% of negatively charged phospholipids (PS, PA, PI, or PG) to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) vesicles increased the electrostatic interactions between calcium ion and the vesicles and large aggregates were formed. In the presence of cholesterol, large aggregates of about 250–350 nm appeared during storage at +4 and −18 °C for more than 1 day.

The effect of liposome storage temperature on phospholipid coatings applied in capillary electrophoresis (CE) was studied by measuring the electroosmotic flow (EOF). EPC coatings with and without cholesterol, PS, or calcium chloride, prepared from liposomes stored at +25, +4, and −18 °C, were studied at 25 °C. The performances of the coatings were further evaluated with three uncharged compounds. Only minor differences were observed between the same phospholipid coatings, showing that phospholipid coatings in CE are relatively insensitive to storage at +25, +4 °C or −18 °C.     

Parallel supported synthesis of polyamine-imidazole conjugates

[reaction: see text] A small collection of nine polyamine-imidazole conjugates, potentially acting as RNases A mimics, has been synthesized on SynPhase lanterns using amino alcohols and diamines as building blocks. Couplings were performed via S(N)2 alkylation of methanesulfonates with amines. The final introduction of N-4-nitrobenzyloxycarbonyldiamines allowed easy purification of the cleaved compounds.