Showing papers by "Max Planck Society published in 1985"

Structure of the protein subunits in the photosynthetic reaction centre of Rhodopseudomonas viridis at 3Å resolution

Abstract: The molecular structure of the photosynthetic reaction centre from Rhodopseudomonas viridis has been elucidated using X-ray crystallographic analysis. The central part of the complex consists of two subunits, L and M, each of which forms five membrane-spanning helices. We present the first description of the high-resolution structure of an integral membrane protein.

Supercoil sequencing: a fast and simple method for sequencing plasmid DNA

Abstract: A method for obtaining sequence information directly from plasmid DNA is presented. The procedure involves the rapid preparation of clean supercoiled plasmid DNA from small bacterial cultures, its complete denaturation by alkali, and sequence determination using oligodeoxyribonucleotide-primed enzymatic DNA synthesis in the presence of dideoxynucleoside triphosphates. The advantages of the method include speed, simplicity, avoidance of additional cloning steps into single-stranded phage M13 vectors, and hence applicability to sequencing large numbers of samples.

Human insulin receptor and its relationship to the tyrosine kinase family of oncogenes

Abstract: We have deduced the entire 1,370-amino-acid sequence of the human insulin receptor precursor from a single complementary DNA clone. The precursor starts with a 27-amino-acid signal sequence, followed by the receptor α-subunit, a precursor processing enzyme cleavage site, then the β-subunit containing a single 23-amino-acid transmembrane sequence. There are sequence homologies to human epidermal growth factor receptor and the members of the src family of oncogene products.

1H NMR Chemical shift selective (CHESS) imaging

Abstract: 1H NMR images of human or animal tissues reflect the spatial distribution of both water (H2O) and methylene (CH2) proton resonance signals. There are several reasons for a separation of these contributions: (i) the large chemical shift dispersion in high magnetic fields (>or=1.5 T) which leads to an apparent spatial shift in 'composite' images between the superimposed H2O and CH2 images; (ii) the evaluation and interpretation of proton H2O and CH2 relaxation times from NMR images; and (iii) the physiological implications of 'water' and 'fat' distributions for medical diagnosis. The authors describe a chemical shift selective (CHESS) imaging technique which destroys the unwanted signal component by means of a selective 90 degrees excitation pulse and a subsequent magnetic field gradient ('homogeneity spoiling gradient') prior to imaging of the wanted component. The new method allows the creation of either a pure 'water' or 'fat' image.

Weak localization and coherent backscattering of photons in disordered media.

Abstract: On trouve que l'intensite diffusee est augmentee jusqu'a 75% a l'interieur d'un cone etroit centre sur la direction de retrodiffusion

The rapid generation of oligonucleotide-directed mutations at high frequency using phosphorothioate-modified DNA

Abstract: M13 RF IV DNA may be prepared in vitro to contain phosphorothioate-modified internucleotidic linkages in the (-)strand only. Certain restriction enzymes react with this modified DNA to hydrolyze the (+)strand exclusively when a phosphorothioate linkage occurs at the normal cleavage point in the (-)strand. The reaction of Pvu I with M13mp2 RF IV DNA containing dCMPS residues in the (-)strand is of this type, and is exploited to allow subsequent digestion with exonuclease III of a portion of the (+)strand opposite different mutagenic mismatched oligonucleotide primers. Two methods are described by which this approach has been used to produce mutations in M13mp2 phage DNA with high efficiency as a result of simple and rapid in vitro manipulations. Plaques containing mutant phage in a genetically-pure form are obtained at a frequency of 40-66%, allowing their characterisation directly by sequence analysis without prior screening and plaque purification. The wide applicability of this approach is discussed.

One-atom maser

Abstract: The exchange of photons between single Rydberg atoms and a single mode of a superconducting cavity with a quality factor $Q=8\ifmmode\times\else\texttimes\fi{}{10}^{8}$ at 2 K was observed. Signals could still be detected with an average number of only 0.06 atom simultaneously in the cavity. With one Rydberg atom the linewidth of the maser transition at about 21 GHz was power broadened and at higher densities asymmetry of the transition was observed, which is ascribed to an ac Stark effect.

A first course in general relativity

Abstract: Clarity, readability and rigor combine in the second edition of this widely-used textbook to provide the first step into general relativity for undergraduate students with a minimal background in mathematics. Topics within relativity that fascinate astrophysical researchers and students alike are covered with Schutz's characteristic ease and authority - from black holes to gravitational lenses, from pulsars to the study of the Universe as a whole. This edition now contains discoveries by astronomers that require general relativity for their explanation; a revised chapter on relativistic stars, including new information on pulsars; an entirely rewritten chapter on cosmology; and an extended, comprehensive treatment of modern detectors and expected sources. Over 300 exercises, many new to this edition, give students the confidence to work with general relativity and the necessary mathematics, whilst the informal writing style makes the subject matter easily accessible. Selected solutions for instructors are available under Resources.

Computations and Parameterizations of the Nonlinear Energy Transfer in a Gravity-Wave Specturm. Part II: Parameterizations of the Nonlinear Energy Transfer for Application in Wave Models

Abstract: Four different parameterizations of the nonlinear energy transfer Snl in a surface wave spectrum are in investigated. Two parameterizations are based on a relatively small number of parameters and are useful primarily for application in parametrical or hybrid wave models. In the first parameterization, shape-distortion parameters are introduced to relate the distribution Snl for different values of the peak-enhancement parameter γ. The second parameterization is based on an EOF expansion of a set of Snl computed for a number of different spectral distributions. The remaining two parameterizations represent operator forms that contain the same number of free parameters as used to describe he wave spectrum. Such parameterizations with a matched number of input and output parameters are required for numerical stability in high-resolution discrete spectral models. A cubic, fourth-order diffusion-operator expression derived by a local-interaction expansion is found to be useful for understanding many ...

Complementary DNA Sequences of Ovarian Follicular Fluid Inhibin Show Precursor Structure and Homology With Transforming Growth Factor-Beta

Abstract: Inhibin, a specific and potent polypeptide inhibitor of the secretion of follicle-stimulating hormone (FSH)1, of gonadal origin and thus a potential contraceptive, may constitute a missing link in the mechanism controlling the differential secretion of the pituitary gonadotropins. Inhibin-like bioactivity has been reported in various fluids and extracts of testis2–5 and in ovarian follicular fluid6–10. Although there have been several attempts to purify inhibin from seminal plasma11–13, purification from follicular fluid has been more successful (refs 14–16; for review see ref. 17). We have previously isolated two forms (A and B) of inhibin from porcine follicular fluid14. Each form comprised two dissimilar subunits of relative molecular mass (Mr) 18,000 (18K, referred to here as the α-subunit) and 14K (the β-subunit), crosslinked by one or more disulphide bridges(s). Forms A and B differ in the N-terminal sequence of their 14K subunit. Preliminary structural characterization of porcine15 and bovine16 ovarian inhibins shows that they have similar properties. Here, we have used the N-terminal amino-acid sequence data on the subunits of each inhibin to identify cloned complementary DNAs encoding the biosynthetic precursors and report that inhibins are the product of a gene family that also includes transforming growth factor-β (TGF-β) and whose structural organization is similar to that of pituitary and placental glycoprotein hormones.

Vacuum states in de Sitter space.

Abstract: We examine possible vacuum states for scalar fields in de Sitter space, concentrating on those states (1) invariant under the de Sitter group O(1,4) or (2) invariant under one of its maximal subgroups E(3). For massive fields there is a one-complex-parameter family of de Sitter-invariant states, which includes the ``Euclidean'' vacuum state as a special case. We show these states are generated from the Euclidean vacuum by a frequency-independent Bogoliubov transformation, and obtain formulas for the symmetric, antisymmetric, and Feynman functions. In the massless minimally coupled case we prove that there exists no de Sitter-invariant Fock vacuum state. However one can find Fock states which are E(3) invariant. These states include the Bunch-Davies and Ottewill-Najmi vacua as special cases.

Drosophila Mushroom Body Mutants are Deficient in Olfactory Learning

Abstract: Two Drosophila mutants are described in which the connections between the input to and the output from the mushroom bodies is largely interrupted. In all forms of the flies (larva, imago, male, female) showing the structural defect, olfactory conditioning is impaired. Learning is completely abolished when electroshock is used as reinforcement and partially suppressed in reward learning with sucrose. No influence of the mushroom body defect on the perception of the conditioning stimuli or on spontaneous olfactory behavior is observed. The defect seems not to impair learning of color discrimination tasks or operant learning involving visual cues.

Black hole normal modes - A semianalytic approach

Abstract: A new semianalytic technique for determining the complex normal mode frequencies of black holes is presented. The method is based on the WKB approximation. It yields a simple analytic formula that gives the real and imaginary parts of the frequency in terms of the parameters of the black hole and of the field whose perturbation is under study, and in terms of the quantity (n + 1/2), where n = 0, 1, 2,... and labels the fundamental mode, first overtone mode, and so on. In the case of the fundamental gravitational normal modes of the Schwarzschild black hole, the WKB estimates agree with numerical results to better than 7 percent in the real part of the frequency and 0.7 percent in the imaginary part, with the relative agreement improving with increasing angular harmonic. Carried to higher order the method may provide an accurate and systematic means to study black hole normal modes.

The Role of Hydrothermal Synthesis in Preparative Chemistry

Abstract: “Hydrothermal synthesis” usually refers to heterogeneous reactions in aqueous media above 100°C and 1 bar. The previously common distinction between hydrothermal conditions below and pneumatolytic conditions above the critical point is no longer made, since no discontinuities are observed upon exceeding the critical conditions. Under hydrothermal conditions, reactants otherwise difficult to dissolve go into solution as complexes, in whose formation water itself or very soluble “mineralizers” can participate. Thus, one can obtain the conditions of chemical transport reactions,[1] of which hydrothermal syntheses can be considered a special case. During recent decades in the geological sciences—in which the method is also historically rooted—it has received a strong impulse, whose effect on preparative solid state chemistry is discussed here.

Fast events in single-channel currents activated by acetylcholine and its analogues at the frog muscle end-plate

Abstract: The fine structure of ion-channel activations by junctional nicotinic receptors in adult frog muscle fibres has been investigated. The agonists used were acetylcholine (ACh), carbachol (CCh), suberyldicholine (SubCh) and decan-1,10-dicarboxylic acid dicholine ester (DecCh). Individual activations (bursts) were interrupted by short closed periods; the distribution of their durations showed a major fast component ('short gaps') and a minor slower component ('intermediate gaps'). The mean duration of both short and intermediate gaps was dependent on the nature of the agonist. For short gaps the mean durations (microseconds) were: ACh, 20; SubCh, 43; DecCh, 71; CCh, 13. The mean number of short gaps per burst were: ACh, 1.9; SubCh, 4.1; DecCh, 2.0. The mean number of short gaps per burst, and the mean number per unit open time, were dependent on the nature of the agonist, but showed little dependence on agonist concentration or membrane potential for ACh, SubCh and DecCh. The short gaps in CCh increased in frequency with agonist concentration and were mainly produced by channel blockages by CCh itself. Partially open channels (subconductance states) were clearly resolved rarely (0.4% of gaps within bursts) but regularly. Conductances of 18% (most commonly) and 71% of the main value were found. However, most short gaps were probably full closures. The distribution of burst lengths had two components. The faster component represented mainly isolated short openings that were much more common at low agonist concentrations. The slower component represented bursts of longer openings. Except at very low concentrations more than 85% of activations were of this type, which corresponds to the 'channel lifetime' found by noise analysis. The frequency of channel openings increased slightly with hyperpolarization. The short gaps during activations were little affected when (a) the [H+]o or [Ca2+]o were reduced to 1/10th of normal, (b) when extracellular Ca2+ was replaced by Mg2+, (c) when the [Cl-]i was raised or (d) when, in one experiment on an isolated inside-out patch, the normal intracellular constituents were replaced by KCl. Reduction of [Ca2+]O to 1/10 of normal increased the single-channel conductance by 50%, and considerably increased the number of intermediate gaps. No temporal asymmetry was detectable in the bursts of openings. Positive correlations were found between the lengths of successive apparent open times at low SubCh concentrations, but no correlations between burst lengths were detectable. The component of brief openings behaves, at low concentrations, as though it originates from openings of singly occupied channels.(ABSTRACT TRUNCATED AT 400 WORDS)

Layered convection induced by phase transitions

Abstract: We report a systematic study on the conditions under which an endothermic phase transition can enforce layered convection. Two-dimensional numerical calculations of convection in a domain containing a divariant phase change were performed in the framework of the “extended Boussinesq approximation,” i.e., considering the effects of adiabatic gradient, latent heat, and frictional heating in the energy equation. We find that the critical value of the negative Clapeyron slope, which must be surpassed in order to induce layered convection, decreases in magnitude with increasing Rayleigh number Ra in the range 104 ≤ Ra ≤ 2×106. Near the critical Clapeyron slope, vacillations between double- and single-layer convection or strongly leaking double-layer convection are possible. The breakdown into layers is influenced very little by the latent heat release but depends solely on the phase boundary deflection caused by lateral temperature differences. The value of the critical Clapeyron slope also seems little affected by the width of the transition zone or by its depth. A possible superplastic rheology within the transition zone would tend to favor layered convection. Scaling the model results to the 670-km discontinuity in the earth's mantle as a possible endothermic phase boundary, we estimate the critical Clapeyron slope to be in the range of −4 to −8 MPa/K (−40 to −80 bar/K). The possibility that the spinel → perovskite + periclase transition is within this range appears to be remote but certainly cannot be neglected.

Clear background and highly sensitive protein staining with Coomassie Blue dyes in polyacrylamide gels: A systematic analysis

Abstract: A systematic analysis of protein staining in polyacrylamide gels with Coomassie Brilliant Blue (CBB) R-250 and G-250 using a high resolution densitometer allowing for quantitative measurements during staining and destaining has revealed that none of the published procedures allows quantitative measurements. Protein staining with CBB R-250 in methanol/water/acetic acid is poor, as is staining with CBB G-250 in trichloroacetic acid or perchloric acid, the latter two, however, allowing for a weak background staining. Consequently using the colloidal properties of the CBB dyes, stronger for G-250 than for R-250, it is possible to increase the sensitivity of protein staining to a detection limit of 0.7 ng bovine serum albumin/mm2 gel. In addition, sensitive protein staining on a clear background is possible. Recipes are described (Section 3.11) for intensified protein staining with CBB G-250 using trichloroacetic acid or perchloric acid on a clear background. Optimal staining of proteins on a clear background can be performed with phosphoric acid and CBB G-250 in the presence of ammonium sulfate since under these conditions the colloidal state of the dye is optimized. Furthermore, conditions are described which allow the stable fixation of the protein-dye complex. Combining the optimized staining conditions with the stable fixation in 20% ammonium sulfate allows for stepwise staining for e. g. detection of weak spots in addition to intense protein spots. The dependence of different staining procedures on gel thickness, gel concentration and compounds routinely used in polyacrylamide gel electrophoresis is also analysed. Calibration curves and application of the new procedure to biological material demonstrate its wide applicability. Convincing arguments for the colloidal properties of the CBB dyes are presented, formulating the rationale for intensified protein staining with CBB dyes in polyacrylamide gels without background staining.

The J1 glycoprotein--a novel nervous system cell adhesion molecule of the L2/HNK-1 family.

Abstract: The neural cell adhesion molecules L1 and N-CAM share a common carbohydrate epitope that is recognized by the monoclonal antibodies L2 and HNK-1. The L2/HNK-1 epitope is also present on the myelin-associated glycoprotein (MAG) which is thought to mediate surface interactions between the axon and myelinating cell. Other, as yet unidentified, cell-surface glycoproteins are recognized by the two antibodies and are believed to belong to a family of neural cell adhesion molecules. To test this hypothesis, we have prepared polyclonal antibodies to a prominent member of the L2/HNK-1 family, the 160K (relative molecular mass (Mr)160,000) glycoprotein. Here we report that these antibodies, designated J1 antibodies, react with astrocytes and oligodendrocytes and interfere with neurone-astrocyte adhesion, but not with neurone-neurone or astrocyte-astrocyte adhesion. This result suggests the involvement of the J1 antigen in cell-cell interactions.

Origin of structure in the Universe.

Abstract: It is assumed that the Universe is in the quantum state defined by a path integral over compact four-metrics. This can be regarded as a boundary condition for the wave function of the Universe on superspace, the space of all three-metrics and matter field configurations on a three-surface. We extend previous work on finite-dimensional approximations to superspace to the full infinite-dimensional space. We treat the two homogeneous and isotropic degrees of freedom exactly and the others to second order. We justify this approximation by showing that the inhomogeneous or anisotropic modes start off in their ground state. We derive time-dependent Schr\"odinger equations for each mode. The modes remain in their ground state until their wavelength exceeds the horizon size in the period of exponential expansion. The ground-state fluctuations are then amplified by the subsequent expansion and the modes reenter the horizon in the matter- or radiation-dominated era in a highly excited state. We obtain a scale-free spectrum of density perturbations which could account for the origin of galaxies and all other structure in the Universe. The fluctuations would be compatible with observations of the microwave background if the mass of the scalar field that drives the inflation is ${10}^{14}$ GeV or less.

Volitional Mediators of Cognition-Behavior Consistency: Self-Regulatory Processes and Action Versus State Orientation

Abstract: One of the most striking discrepancies between everyday experience and psychological theorizing concerns the complexity of motivational states. While most psychologists tend to focus on a single behavioral domain (e.g., achievement, affiliation, eating, learning, problemsolving, sex, etc.), we know from everyday experience that people very rarely seem to have just one behavioral inclination in a given situation. In everyday life people usually experience several motivational tendencies simultaneously and more often than not have multiple commitments to a variety of goals. At first glance our task — to explain and predict which of the competing action tendencies a person actually will implement in a given situation — seems to boil down to the objective of establishing the dominant (i. e., strongest) action tendency among all the competing tendencies (e. g., Atkinson & Birch, 1970).

The ring laser gyro

Abstract: This paper presents a review of both active and passive ring laser devices. The operating principles of the ring laser are developed and discussed, with special emphasis given to the problems associated with the achievement of greater sensitivity and stability. First-principle treatments of the nature of quantum noise in the ring laser gyro and various methods designed to avoid low-rotation-rate lock-in are presented. Descriptions of state-of-the-art devices and current and proposed applications (including a proposed test of metric theories of gravity using a passive cavity ring laser) are given.

Synthetic and natural Escherichia coli free lipid A express identical endotoxic activities

Abstract: The recently chemically synthesized Escherichia coli lipid A and the natural free lipid A of E. coli were compared with respect to their endotoxic activities in the following test systems: lethal toxicity, pyrogenicity, local Shwartzman reactivity, Limulus amoebocyte lysate gelation capacity, tumour necrotizing activity, B cell mitogenicity, induction of prostaglandin synthesis in macrophages, and antigenic specificity. It was found that synthetic and natural free lipid A exhibit identical activities and are indistinguishable in all tests.

Motivational properties of kappa and mu opioid receptor agonists studied with place and taste preference conditioning.

Abstract: The reinforcing properties of various opioid agonists acting preferentially on the kappa and mu opioid receptors were assessed using taste and place preference conditioning procedures.