Preparation of asymmetric,cerebroside sulfate-containing phospholipid vesicles

A procedure is described which inserts asymmetrically cerebroside sulfate (‘sulfatide’) into the outer leaflet of bilayered phospholipid vesicles. Cerebroside sulfate is adsorbed onto a cellulose, filter-paper support and, when incubated with phosphatidylcholine vesicles is transferred to and inserted into the outer leaflet of these vesicles. This transfer occurs at, or above the transition temperature of the phospholipid and follows a similar pattern with small or larger (‘fused’) unilamellar vesicles. The transfer is linear with time for 1–2 h and is maximal after about 6 h, when the sulfatide content reaches about 6 mol% of the total quantity of phospholipid, corresponding to about 10 mol% of the phospholipids present in the outer layer. Initial rates of sulfatide transfer were somewhat increased when the vesicles contained a positively charged lipid (e.g. stearylamine) and decreased when this lipid was negatively charged (e.g. dicetyl phosphate) or hydrophobic (e.g. cholesterol). Divalent ions markedly inhibited sulfatide transfer and monovalent ions did so to a lesser degree. Once incorporated into the outer leaflet of the vesicle, the sulfatide could not be removed by washing with buffer, 1 M NaCl or 1 M urea.     

C-n.m.r. spectral study of C reductively methylated glycopeptides derived from glycophorin A

¹³C-n.m.r. spectral data for ¹³C reductively methylated intact homozygous and heterozygous glycophorins A were compared with the ¹³C-n.m.r. spectral data for the ¹³C reductively methylated homozygous and heterozygous N-terminal glycopeptides derived from the trypsin digest of glycophorin A. The results indicate that pronounced aggregation of this glycoprotein in solution does not affect the structural differences that we have previously observed for glycophorins A^M and A^N at and/or near the N-terminal amino acid. Moreover, the data suggest that two structural states exist for glycophorin A^M.     

Comparative titration of arginyl residues in purified D-β-hydroxybutyrate apodehydrogenase and in the reconstituted phospholipid-enzyme complex

In order to titrate and understand the role of arginyl residues of D-β-hydroxybutyrate dehydrogenase, arginyl specific reagents: butanedione, 1,2-cyclohexanedione and phenylglyoxal were incubated with three different forms of the enzyme; native enzyme (inner mitochondrial membrane bound), purified apoenzyme (phospholipid -free) and phospholipid-enzyme complex (reconstituted active form).After complete inactivation of the enzyme by [¹⁴C]-phenylglyoxal, the number of modified arginyl residues was different: one with the lipid-free apoenzyme and three with the phospholipid-enzyme complex, suggesting a conformational change of the enzyme triggered by the presence of phospholipids.After exhaustive chemical modification either of the apoenzyme or of the phospholipid-enzyme complex with [¹⁴C]-phenylglyoxal, four arginyl residues were titrated indicating that these residues are located in the hydrophilic part of the enzyme, not interacting with phospholipids.Reconstituted enzyme inactivated by butanedione could no longer bind a pseudosubstrate (succinate) which indicates that an arginyl residue is involved in the enzyme-substrate complex formation.The values of second order rate constants of D-β-hydroxybutyrate dehydrogenase inactivation by butanedione and 1,2-cyclohexanedione were unchanged with the three enzyme forms, suggesting that phospholipids are not involved in the substrate binding mechanism.     

Die Rezeptoren an den ersten Antennen vonLeptestheria dahalacensis Rüppel (Crustacea,Conchostraca)

Zusammenfassung Bei dem ConchostracenLeptestheria dahalacensis kommen auf den ersten Antennen etwa 600 gleich aussehende Sinneshaare vor, die in Gruppen von jeweils 25–30 zusammengefaßt sind. Diese Sinneshaare sind in zwei Teile gegliedert, die durch das lichtmikroskopisch gut sichtbare Basalstück (basal bead) voneinander getrennt sind. Dieses bildet die Basis des Haares, dessen Wand im wesentlichen aus Epicuticula besteht. Apikal wird das Haar durch das Endkügelchen (terminal pellet) abgeschlossen. Das Basalstück wird von der untersten Lage der Epicuticula gebildet. Die 4–10 Receptorcilien, die jeweils einzeln ebensovielen Dendriten aufsitzen, ziehen aus dem inneren Teil des Rezeptors, der von insgesamt 5 Hüllzellen umgeben wird, durch das Basalstück, in dem sie stark eingeengt werden und verzweigen sich dann im äußeren Teil des Rezeptors. Sie ziehen bis zum Endkügelchen, in das sie durch einen Porus, den man als Häutungsporus ansprechen kann, eintreten. In der Häutungsvorbereitung wird der Haarbalg von der Hüllzelle 5, das Basalstück von der Hüllzelle 4, der Haarschaft dagegen von der Hüllzelle 3 gebildet. Dabei spaltet sich die Hüllzelle 3 ringspaltförmig auf, so daß in diesem Spalt der neuangelegte Haarschaft handschuhfingerförmig eingestülpt liegt. Die Hüllzelle 2 formt die Spitze des neuen Haares, während die Dendritenscheide von der Hüllzelle 1 abgegeben wird.

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The receptors on the first antennae ofLeptestheria dahalacensis Rüppel (Crustacea, Conchostraca)

Summary On the antennulae ofLeptestheria dahalacensis (Conchostraca) nearly 600 sensory setae of one type are found. They are gathered in groups of 25–30. The single sensory seta is divided into two parts by the basal bead which is easily visible in the light microscope. The basal bead is the socket of the seta, whose wall is mainly built up by the epicuticle. The terminal pellet closes the tip of the seta. The basal bead is derived from the innermost layer of the epicuticle. 4–10 dendrites each with one receptorcilium innervate the receptor. The receptorcilia stretch through the interior part of the receptor and the basal bead into the exterior part, where they branch. They enter the terminal pellet in a porus, which seems to be a moulting porus. The interior part of the receptor is surrounded by 5 sheath cells. During the premoult it becomes obvious, that the socket of the seta is built by the sheath cell 5, the basal bead by the sheath cell 4 and the shaft by the sheath cell 3. For this the sheath cell 3 is divided into two parts. Between this two parts the newly formed cuticle is invaginated. The sheath cell 2 formes the tip and the sheath cell 1 the cuticular sheath of the new bristle.