Showing papers by "University of Basel published in 1979"

Structural dynamics in phospholipid bilayers from deuterium spin–lattice relaxation time measurements

Abstract: The quadrupolar spin–lattice (T1) relaxation of deuterium labeled phospholipid bilayers has been investigated at a resonance frequency of 54.4 MHz. T1 measurements are reported for multilamellar dispersions, single bilayer vesicles, and chloroform/methanol solutions of 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine (DPPC), selectively deuterated at ten different positions in each of the fatty acyl chains and at the sn‐3 carbon of the glycerol backbone. At all segment positions investigated, the T1 relaxation times of the multilamellar and vesicle samples of DPPC were found to be similar. The profiles of the spin–lattice relaxation rate (1/T1) as a function of the deuterated chain segment position resemble the previously determined order profiles [A. Seelig and J. Seelig, Biochem. 13, 4839 (1974)]. In particular, the relaxation rates are approximately constant over the first part of the fatty acyl chains (carbon segments C3–C9), then decreasing in the central region of the bilayer. In chloroform/methanol solution, by contrast, the relaxation rates decrease continuously from the glycerol backbone region to the chain terminal methyl groups. The contributions from molecular order and motion to the T1 relaxation rates have been evaluated and correlation time profiles derived as a function of chain position. The results suggest that the motions of the various methylene segments are correlated in the first part of the fatty acyl chains (C3–C9), occurring at frequencies up to 1/τc?1010 Hz. Beyond C9, the rate and amplitude of the chain segmental motions increase, approaching that of simple paraffinic liquids in the central region of the bilayer (1/τc?1011 Hz). The T1 relaxation rates of multilamellar dispersions of 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) deuterated at the 9, 10 double bond of the sn‐2 chain were also determined and found to be significantly faster than those of the CD2 chain segments of DPPC bilayers. This is most likely due to the larger size and correspondingly slower motion of the chain segment containing the double bond. At segments close to the lipid–water interface the rate of motion is considerably less than in the hydrocarbon region of the bilayer.

Metal ion/buffer interactions. Stability of binary and ternary complexes containing 2-amino-2(hydroxymethyl)-1,3-propanediol (Tris) and adenosine 5'-triphosphate (ATP).

Abstract: The acidity constant of protonated 2-[bis(2-hydroxyethyl)amino]-2(hydroxymethyl)-1,3-propanediol (Bistris) has been measured. The influence of hydroxo groups on the basicity of Bistris and related bases is discussed. The interaction of Bistris with the metal ions (M2+) Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+ was studied by potentiometry and spectrophotometry in aqueous solution (I= 1.0 M, KNO3; 25°C) and the stability constants of the M(Bistris)2+ complexes were determined. Unexpectedly Ca(Bistris)2+ is the most stable among the alkaline earth ion complexes (log Kcaca(Bistris)= 2.25; the corresponding values for the Mg2+, Sr2+ and Ba2+ complexes are 0.34, 1.44 and 0.85, respectively). The ions of the 3d series follow the Irving-Williams sequence: log KMnMn(Bistris)= 0.70, for Cu2+ 5.27 and Zn2+ 2.38. Ternary complexes containing ATP4- as a second ligand were also investigated: the values for Δlog KM (= log KM(ATP)M(ATP)(Bistris)–log KMM(Bistris)) are in general negative (e.g. Δlog KCa= -0.40 or Δllog KCu= - 1.65), thus indicating that the interaction of Bistris with M(ATP)2- is somewhat less pronounced than with M2+. However, even in mixed-ligand systems, complex formation may still be considerable, hence great reservations should be exercised in employing Bistris as a buffer in systems containing metal ions. Moreover, in several cases Δlog Km is relatively high [for Mg2+-ATP4- Bistris even positive], indicating some cooperativity between the coordinated ligands, possibly hydrogen-bond formation. Distributions of the complexes in dependence on pH are given, and the structures of the binary M (Bistris)2+ and the ternary M(ATP) (Bistris)2- complexes are discussed. The participation of Bistris hydroxo groups in complex formation is evident.

Keratin formation and barrier mechanisms in the epidermis of Natrix natrix (Reptilia: Serpentes): An ultrastructural study.

Abstract: A β-keratin pattern, consisting of 30 A filaments embedded in an amorphous matrix, is formed by fusion of membrane-bound packets with the 70 A filaments of immature cells. This pattern occurs in the Oberhautchen and the β-layer. When completely mature, these two components show no cell boundaries. It is suggested that this feature is associated with the process that leads to the separation of outer and inner epidermal generation. Filaments of 100-150 A embedded in an amorphous matrix form the α-keratin pattern, which occurs in the α-layer only. The lacunar tissue is regarded as consisting of cells resembling immature α-cells, whereas mesos and clear layer show a keratin-like material consisting of 100-150 A filaments without matrix. This is regarded as a modification of α-keratin. The cells of all components synthesizing α-keratin (α, mesos and clear layer) have the following features in common: (1) the plasma membrane is modified in that its inner leaflet is obscured by the deposition of a marginal layer, and (2) the cells have 0.06-0.1 μm mucous granules containing mucopolysaccharides, which release their content into the intercellular space. Protective and barrier functions of the epidermis are provided by the following features: (1) Oberhautchen and β-layer merge during final maturation to a homogenous stratum of β-keratin without intercellular spaces. Their function seems to be mechanical protection. (2) The marginal layer of α-keratin containing cells, which decreases in thickness from without inwards, is highly resistant to physical and chemical influences. (3) Mesos granules contain phos-pholipid-lamellae, which are partly discharged into the intercellular space and partly remain within the mesos cells. These lipid lamellae are believed to contribute to the establishment of the permeability barrier. (4) The content of mucous granules may play a role in immunological processes. (5) Tight junctions seal off the intercellular space between the uppermost living cells of the epidermis and contribute to the permeability barrier.

Photocurrents generated by bacteriorhodopsin on planar bilayer membranes

Abstract: When purple-membrane fragments from Halobacterium halobium are added to one aqueous phase of a positively-charged black lipid membrane, the membrane becomes photoelectrically active. Under normal conditions the steady-state photo-current is extremely low, but increases considerably when the lipid bilayer is doped with proton-permeable gramicidin channels or with a lipophilic acid-base system. These findings indicate that the purple-membrane sheets are bound to the surface of the bilayer, forming a sandwich-like structure. The time-behaviour of the photocurrent may be interpreted on the basis of a simple equivalent circuit which contains the conductance and capacitance of the purple membrane in series with the conductance and capacitance of the lipid bilayer. From the dependence of the photocurrent on the polarization of the exciting light the average angle between the transition moment of the retinal chromophore and the plane of the bilayer was calculated to be about 28 degrees. Furthermore, it was shown that chromophore-free apomembrane binds to the lipid bilayer and that its photoelectrical activity can be restored in situ by adding all-trans-retinal to the aqueous phase.

Ultrastructural and radiotracer studies of pore function in foraminifera

Abstract: Clusters of mitochondria have been observed close to the inner end of the pores in Nonionella stella, Globobulimina pacifica, Buliminella tenuata, Bolivina argentea, Loxostomum pseudobeyrichi, Cassidulinoides cornuta and Bolivina cf. subexcavata, pointing to a pore function of oxygen-uptake. The relationship between mitochondria and pores is most distinct in Buliminella tenuata, Bolivina argentea and L. pseudobeyrichi collected from a deep-water, low-oxygen environment. Amphistegina lobifera Larsen, 1976 readily took up 14CO2 through its pores, indicating a pore function related to the photosynthetic activities of its symbionts. 14C-labelled glucose did not pass through the pores in traceable amounts during a 2 h exposure time.

Inclusive electron scattering from he-3

Abstract: Data on inclusive electron scattering from $^{3}\mathrm{He}$ over a large range of momentum transfer (2-7 ${\mathrm{fm}}^{\ensuremath{-}1}$) are presented and compared with a one-nucleon knockout calculation based on a Faddeev spectral function.

A Catalogue of Galaxies within 10 MPC

Abstract: A catalogue is given of the 179 known galaxies within 10 Mpc. The inclusion of a galaxy depends on its redshift (v0 ≤ 500 km s−1) or, in the case of 7 dwarf galaxies, on the fact that their distances are known to be small. The catalogue contains in addition 52 more distant galaxies with v0 ≤ 500 km s−1: 50 are bona fide Virgo cluster members and 2 are members of the Leo group. Positions, types, absorption-corrected luminosities, and velocities are given for the catalogue galaxies. The catalogue is believed to be nearly complete for galaxies brighter than ∽ – 18m.5, but it contains also many considerably fainter galaxies. The galaxies within 10 Mpc form the Local Group with 28 members and seven additional groups with a total of 92 known members. 59 galaxies (33%) do not seem to belong to any group. Der Katalog enthalt die 179 bekannten Galaxien innerhalb 10 Mpc. Die Aufnahme einer Galaxie hangt von ihrer Rotverschiebung (v0 ≤ 500 km s−1) oder im Falle von 7 Zwerggalaxien von deren bekannter geringer Entfernung ab. Der Katalog enthalt weiterhin 52 entferntere Galaxien mit v0 ≤ 500 km s−1; davon sind 50 bona fide Mitglieder des Virgohaufens und 2 gehoren zur Leo-Gruppe. Position, Typ, wegen Absorption korrigierte Helligkeit und Geschwindigkeit sind fur jede Galaxie gegeben. Man darf annehmen, das der Katalog fur Galaxien heller als – 18.5ter Grose nahezu komplett ist, jedoch enthalt er auch viele wesentlich schwachere Galaxien. Die Galaxien innerhalb 10 Mpc bilden die lokale Gruppe mit 28 Mitgliedern und 7 weitere Gruppen mit einer Gesamtzahl von 92 bekannten Mitgliedern. 59 Galaxien (33%) scheinen zu keiner Gruppe zu gehoren.

Laserflash‐photolysis of the p‐Chloranil/naphthalene system: Characterization of the naphthalene radical cation in a fluid medium,

Abstract: Excitation of p-Chloranil (CA) in propylcyanide (PrCN) at room temperature leads to rapid production of 3CA* which decays predominantly to CAH· with k = 1.6 · 105 s−1. Observation of a photoinduced current suggests simultaneous production of CA− formed by electron transfer quenching of 3CA* by the medium. Added naphthalene (NP) quenches 3CA* with kq = 7.0 · 109M−1S−1; NP+ is unambigously identified as product (besides CA−) of the electron transfer process. Dissociation of the ion pair occurs with essentially unit probability. Higher concentrations of NP lead to the formation of (NP)+2. Pertinent spectroscopic parameters established for NP+ under the conditions used are λmax = 685 nm (ϵ = 2970) using the known parameters of CA as reference. NP+ and CA decay by charge annihilation with kr = 4.5 · 109M−1S−1. The deviation from the diffusion controlled rate constant expected for ionic species, is discussed in view of the spin characteristics of the process. Comparison with two other ion recombination reactions leads to the conclusion that ‘inverted behaviour’ as expected from Marcus' theory does also not show up for backward e−-transfer between two ions (produced by forward e−-transfer between two neutrals). Residual absorptions in the system are ascribed to CAH·, tentatively proposed to originate from H+-abstraction by CA from the solvent. NP+ appears to be a rather stable species with respect to the medium if the latter is meticulously purified.

An Adenosine Triphosphatase Isolated from Chromaffin-Granule Membranes is Closely Similar to F1-Adenosine Triphosphatase of Mitochondria

Abstract: 1 An ATPase purified with high yield from bovine chromaffin granules closely resembles the mitochondrial F1-ATPase from bovine heart or bovine adrenal medulla with respect to the following properties: apparent molecular weight on gel filtration, subunit composition on dodecyl- sulphate/polyacrylamide gel electrophoresis, cross-reaction with an antiserum directed against F1-ATPase from bovine heart mitochondria, and proteolytic fingerprints of the three largest subunits. 2 The chromaffin granule ATPase could, however, be distinguished from the mitochondrial enzyme: it did not enhance the fluorescence of aurovertin and reacted differently from mitochondrial F1-ATPase in quantitative complement fixation. 3 The following three arguments make it unlikely that the ATPase isolated from chromaffin granules has been artifically dislodged from mitochondria during fractionation: (a) mitochondrial contamination of the purified chromaffin granule membranes was bhow 2%; (b) the purification procedure solubilized at least two thirds of the total ATPase activity of these membranes; (c) an antiserum directed against bovine mitochondrial F1-ATPase inhibited the ATP-driven uptake of 5-hydroxytryptamine by resealed chromaffin granule ‘ghosts’. 4 The proton-translocating ATPase of chromaffin granules is thus almost identical to mitochondrial F1-ATPase. This finding raises intriguing questions about the evolution of chromaffin granules and about the mechanisms by which the two enzymes are transported to different locations within the same cell.

The mitochondrial COB region in yeast codes for apocytochrome b and is mosaic.

Abstract: Mitochondrial mutants of Succhuromyces cerevisiue defective in cytochrome b were analyzed genetically and biochemically in order to elucidate the role of the mitochondrial genetic system in the biosynthesis of this cytochrome. The mutants mapped between OLIl and OLZ2 on mitochondrial DNA in a region called COB. A fine structure map of the COB region was constructed by rho- deletion mapping and recombination analysis. The combined genetic and biochemical data indicate that the COB region is mosaic and contains at least five distinct clusters of mutants, A-E, with A being closest to OLZ2 and E being closest to OLIl. Clusters A, C and E are probably coding regions for apocytochrome b, whereas clusters B and D seem to be involved in as yet unknown functions. These conclusions rest on the following evidence. 1. Most mutants in clusters A, C and E have specifically lost cytochrome b. Many of them accumulate smaller mitochondrial translation products ; some of these were identified as fragments of apocytochrome b by proteolytic fingerprinting. The molecular weight of these fragments depends on the map position of the mutant, increasing in the direction OLI2+OLII. The mutant closest to OLIl accumulates an apocytochrome b which is slightly larger than that of wild type. 2. A mutant in cluster C exhibits a spectral absorption band of cytochrome b that is shifted 1.5 nm to the red. 3. Mutants in clusters B and D are pleiotropic. A majority of them are conditional and lack the absorption bands of both cytochrome b and cytochrome uu3; these mutants also fail to accumulate apocytochrome b and subunit I of cytochrome c oxidase and instead form a large number of abnormal translation products whose nature is unknown. 4. Zygotic complementation tests reveal at least two complementation groups: The first group includes all mutants in cluster B and the second group includes mutants in clusters (A + C + D + E).

A Membrane Glycoprotein of Aggregating Dictyostelium Cells with the Properties of Contact Sites

Abstract: Aggregating cells of Dictyostelium discoideum form EDTA-stable contacts which are blocked by a Fab (antigen-binding fragment) preparation from antisera raised against membranes. The target site of the blocking Fab fragments has been identified as a specific glycoprotein. In this paper its purification, carbohydrate and amino acid composition are described. Purification was 800-fold, starting with cells lysed by digitonin. The plasma membranes, preserved as ghosts by this treatment, were purified in a two-phase system and extracted with butan-1-ol. The water phase contained predominantly concanavalin-A-binding glycoproteins and was particularly rich in contact sites A. These were further purified on DE-cellulose and sucrose gradients. Sodium dodecylsulphate/polyacrylamide gel electrophoresis of the purified material revealed one major glycoprotein band in the molecular weight region of 80 000 to 90 000, depending on the acrylamide concentration. The sugars found in contact sites A were mannose, N-acetylglucosamine, fucose, and possibly glucose. The protein moeity contained 8% proline and was particularly rich in hydroxy amino acids.

Promotion and Limitation of Genetic Exchange

Abstract: Exchange of genetic material has widely been observed in practically all living organisms. This suggests that genetic exchange must have been practised since a long time ago, perhaps ever since life has existed. The rules followed by nature in the exchange of genetic information are studied by geneticists. However, as long as the chemical nature of the genetic material remained unknown, genetics remained a rather abstract branch of the biological sciences. This gradually began to change after Avery et al. (1944) had identified DNA as the carrier of genetic information. Their evidence found an independent support by Hershey and Chase (1952), and it was accepted by a majority of biologists by 1953 when Watson and Crick (1953) presented their structural model of DNA. Hence it was clear 25 years ago that very long, filamentous macromolecules of DNA contained the genes. As is usual in fundamental research, the knowledge acquired pointed to a number of new important questions. Among them were those on the structure and function of genes, but also those on the molecular mechanisms of exchange of genetic material. It is at that time, in the fall of 1953, that I joined more or less by chance a small group of investigators animated by Jean Weigle and Eduard Kellenberg. One of their main interests concerned the mechanisms of genetic recombination. Feeling that the time was not ripe to carry out such studies on higher organisms, they had chosen to work with a bacterial virus, the nowadays famous bacteriophage lambda (A). It is interesting to see today how knowledge acquired in work with phage λ should later strongly influence other research in molecular genetics. In this lecture I would like to trace back to the origin of some discoveries made in the work with A and point to their importance for subsequent investigations. But let met first define in more general terms what I mean by genetic exchange. Escherichia coli and other bacteria carry all their genes on a single, very long DNA molecule, except for occasional cases when bacteria have one or several additional, much shorter DNA molecules, called plasmids, endowed with the ability of autonomous replication. A bacterial strain harbouring besides its chromosome a fertility plasmid F can at times donate by conjugation a copy of its F plasmid to a recipient strain. The F plasmid then establishes itself in the recipient cell as an autonomous plasmid, and it will be propagated in its new environment. The donor strain has thus exchanged genetic information with the recipient strain, and in this case

A novel bacteriophage defence mechanism: the anti-restriction protein.

Abstract: Bacteriophage T3 and T7 protect their DNA from restriction by producing, as the earliest detectable phage functions, anti-restriction proteins Although the two phage proteins differ in their chromatographic and antigenic properties, they act by the same mechanism: the anti-restriction proteins inhibit E coli K12 restriction endonuclease by direct interaction