Showing papers by "ETH Zurich published in 1982"
TL;DR: Calculated distance measurements imply that corresponding distance measurements can be used for resonance assignments in the side-chains of the aromatic amino acid residues, asparagine and glutamine, where the complete spin systems cannot usually be identified from through-bond spin-spin coupling connectivities.
570 citations
TL;DR: The assignment of the 1Hnuclear magnetic resonance spectrum of the basic pancreatic trypsin inhibitor with the use of two-dimensional 1H nuclear magnetic resonance techniques at 500 MHz is described.
542 citations
TL;DR: A general scheme that relies on experimental observation by two-dimensional nuclear magnetic resonance techniques of complete throughbond and through-space proton-proton connectivity maps to obtain sequential resonance assignments for the individual residues in the amino acid sequence is proposed.
541 citations
TL;DR: In this article, the age of Chinese loess deposits has been investigated and a late Pliocene age of ∼2.4 Myr was assigned to the oldest loess sediments measured, based on the intensity variations of natural remanent magnetization (NRM) and low field magnetic susceptibility.
Abstract: The age of Chinese loess deposits has long been disputed. Biostratigraphical and earlier magnetostratigraphical investigations placed the entire loess formation within the Pleistocene. The new palaeomagnetic measurements reported here on a bore hole section near Lochuan (Shaanxi province) suggest a clearly defined magnetic polarity zonation which extends below the Olduvai subchron. A late Pliocene age of ∼2.4 Myr is assigned to the oldest loess sediments measured. The intensity variations of natural remanent magnetization (NRM) and low field magnetic susceptibility are indicative of climatic changes during loess deposition.
535 citations
TL;DR: A new genus of methanogenic bacteria is described, which was isolated from a mesophilic sewage digester and is most probably the filamentous bacterium, earlier referred to asMethanobacterium soehngenii, “fat rod” or “acetate organism”.
Abstract: A new genus of methanogenic bacteria is described, which was isolated from a mesophilic sewage digester. It is most probably the filamentous bacterium, earlier referred to asMethanobacterium soehngenii, “fat rod” or “acetate organism”. The single non-motile, non-sporeforming cells are rod-shaped (0.8×2 μm) and are normally combined end to end in long filaments, surrounded by a sheath-like structure. The filaments form characteristic bundles.Methanothrix soehngenii decarboxylates acetate, yielding methane and carbon dioxide. Other methanogenic substrates (H2−CO2, formate, methanol, methylamines) are not used for growth or methane formation. Formate is split into hydrogen and carbon dioxide. The temperature optimum for growth and methane formation is 37°C and the optimal pH range is 7.4–7.8. Sulfide and ammonia serve as sulfur and nitrogen source respectively. Oxygen completely inhibits growth and methane formation, but the bacteria do not loose their viability when exposed to high oxygen concentrations. 100 mg/l vancomycin showed no inhibition of growth and methanogenesis. No growth and methane formation was observed in the presence of: 2-bromoethanesulfonic acid, viologen dyes, chloroform, and KCN. The bacterium has a growth yield on acetate of 1.1–1.4 g biomass per mol acetate. The apparent “K
S
” of the acetate conversion system to methane and carbon dioxide is 0.7 mmol/l. The DNA base composition is 51.9 mol% guanine plus cytosine. The nameMethanothrix is proposed for this new genus of filamentous methane bacterium. The type species,Methanothrix soehngenii sp. nov., is named in honor of N. L. Sohngen.
451 citations
348 citations
TL;DR: Measurements of the amide proton-C α proton cross-peak intensities in the two-dimensional homonuclear correlated 1 H nuclear magnetic resonance spectra yield exchange rates for the individual amide protons that are for the first time obtained for numerous peptide groups located near the protein surface in the single crystal structure of BPTI.
319 citations
TL;DR: In this article, the relative topicity of approach of reactants is defined as like {Ik} and unlike (ul) if the corresponding descriptor pairs are Re*,Re*. or R*,Re*, and Re*,Si* or R*)Si*, respectively.
Abstract: uous specification of the steric course and the product configuration of diastereoselective reactions. The reflection-invariant relative topicity of approach of reactants is defined as like {Ik) and unlike (ul) if the corresponding descriptor pairs are Re*,Re*. or R*,Re*, and Re*,Si* or R*,Si*, respectively. The descriptor pair notations (Ik and uc) of reactants disclose related steric courses of reactions more often than do the relative configurations of their products, for which the configurational notation I= R*,R* and u= R*,S* is proposed. The advantage of specifying the relative topicity is demonstrated by means of a series of recent examples of importance to the synthetic organic chemist taken from the literature and from our own work. 1. Introduction-The Problem Complex natural products such as macrolides, ionophores, and related compounds have recently become target molecules for synthetic organic chemists[’]. The often formidable array of asymmetric carbon atoms in the structures of these compounds[21 has stimulated the development of highly stereoselective asymmetric syntheses. Foremost amongst these are the ald~l[~-~], nitr~aldoF“~], and Michael additions[81. In all these reactions two planar trigonal carbon atoms are linked together to create a pair of asymmetric tetrahedral carbon atoms [route (a) in Scheme 11. Stereoselective additions to 01efins[~] and to trigonal carbon atoms a to an asymmetric carbon [routes (b) and (c), respectively, in Scheme 11, give the same type of products 1L7.9-121
318 citations
TL;DR: Protein lateral diffusion coefficients measured above the temperature at which the lipid gel-liquid/crystalline phase transition occurs (Tc) are combined with previously determined rotational diffusion coefficients to provide a test of the Saffman-Delbrück equations.
Abstract: Lateral diffusion of bacteriorhodopsin and a lipid analogue has been measured in dimyristoylphosphatidylcholine bilayers as a function of temperature, phospholipid/protein (mol/mol; L/P) ratio, and aqueous phase viscosity. The protein lateral diffusion coefficients measured above the temperature at which the lipid gel-liquid/crystalline phase transition occurs (Tc) are combined with previously determined rotational diffusion coefficients to provide a test of the Saffman-Delbruck equations [Saffman, P. G. & Delbruck, M. (1975) Proc. Natl. Acad. Sci. USA 72, 3111-3113]. Insertion of the diffusion coefficients into these equations enables the protein diameter to be calculated. The value of 4.3 +/- 0.5 nm so obtained is in reasonable agreement with the known structure of bacteriorhodopsin. A 12-fold increase in the viscosity of the aqueous phase reduces protein lateral diffusion coefficients by 50%, which is also consistent with the Saffman-Delbruck equations. Both protein and lipid lateral diffusion coefficients decrease with decreasing L/P ratio above the Tc. It is argued that, at a high L/P ratio, this effect is probably due to changes in membrane viscosity while, at a low L/P ratio, "crowding" effects (steric restrictions) and protein aggregation become important. When comparing diffusion measurements made in different systems, it is important to take the effect of the L/P ratio into account. When this is done, other published measurements of freely diffusing membrane proteins are in good agreement with the present results and the predictions of the Saffman-Delbruck equations. Below the Tc, the presence of protein enhances diffusion rates. The overall effect is to smooth out the large change in diffusion coefficient that occurs at the Tc.
266 citations
TL;DR: The results suggest an intercalative mode of binding, which partially unwinds the DNA, in which 18.6 base-pairs and 6.4 recA monomers contribute to one turn of a right-handed helix.
216 citations
TL;DR: The present work determines the helicity of DNA in the recA complex and finds that the DNA helix follows the protein helix visible in the electron microscope and has 18.6 bp per turn, which corresponds to an unwinding of the DNA double helix by 15° per bp.
Abstract: The RecA protein of Escherichia coli is involved in recombination (for review see ref. 1). The protein binds transiently to double-stranded DNA in the presence of ATP. In the presence of ATPγS, a non-hydrolysable analogue of ATP, rec A–DNA complexes are stable2,3. Duplex DNA in these complexes is stretched by a factor 1.5 (ref. 4), and the complexes appear in the electron microscope as helical filaments with a pitch of ∼100 A and 6.2 recA units per turn covering 18.6 base pairs (bp)5. RecA crystals have a space group of similar helical parameters6. In order to understand the function of recA, it is necessary to describe the conformation of the DNA in the recA complex. Using a topological method, the present work determines the helicity of DNA in the complex. We find that the DNA helix follows the protein helix visible in the electron microscope and has 18.6 bp per turn, which corresponds to an unwinding of the DNA double helix by 15° per bp.
TL;DR: In this paper, the geomagnetic reversal sequence for the entire Paleogene was confirmed and dated for most of this period by using magnetostratigraphy, lithostratigraphic, and biostrigraphic investigations in three sections covering the entire paleogene.
Abstract: The Umbrian sequence of pelagic carbonate rocks provides an opportunity for precise correlation between Paleogene biostratigraphy and geomagnetic polarity history. The red-to-pink, Paleocene to middle Eocene Scaglia Rossa limestone, the varicolored upper Eocene Scaglia Variegata limestone, and the gray-green Oligocene Scaglia Cinerea marlstone form a 250-m-thick, continuous exposure in the Contessa Valley near Gubbio, Italy. Magnetostratigraphic, lithostratigraphic, and biostratigraphic investigations in three sections covering the entire Paleogene have confirmed and dated the geomagnetic reversal sequence for most of this period. The ferromagnetic mineral in the Scaglia Cinerea is magnetite and AF demagnetization to peak fields of 20 mT is sufficient to define the characteristic remanent magnetization. The Scaglia Variegata and pink Scaglia Rossa samples contain an additional hematite component which is very pronounced in dark red Paleocene Scaglia Rossa samples. Changes of magnetic mineralogy take place in these limestones during heating, especially above 500 °C. However, thermal demagnetization is effective in isolating the characteristic remanence vectors, which form almost antipodal clusters of directions representing normal and reversed polarities. The directions are rotated counterclockwise, partly due to post-Oligocene tectonism. Paleontological zonations of planktic foraminifera and calcareous nannofossils were hampered by poor preservation, but the major epoch and stage 29, as in the Gubbio Bottaccione section; Paleocene-Eocene, just above anomaly 25; Eocene-Oligocene, between anomalies 13 and 15; Oligocene-Miocene, just below anomaly 6C. These correlations require slight modifications to previous conclusions on Paleogene sea-floor spreading rates.
TL;DR: The data indicate that at the end of Cretaceous, when a high proportion of the ocean's planktic organisms were eliminated, an associated reduction in productivity led to a partial transfer of dissolved carbon dioxide from the oceans to the atmosphere, which resulted in a large increase of the atmospheric carbon dioxide during the next 50,000 years, which is believed to have caused a temperature rise revealed by the oxygen-isotope data.
Abstract: The latest Mesozoic and earliest Tertiary sediments at Deep Sea Drilling Project site 524 provide an amplified record of environmental and biostratographic changes at the end of Cretaceous. Closely spaced samples, representing time intervals as short as 102 or 103 years, were analyzed for their bulk carbonate and trace-metal compositions, and for oxygen and carbon isotopic compositions. The data indicate that at the end of Cretaceous, when a high proportion of the ocean9s planktic organisms were eliminated, an associated reduction in productivity led to a partial transfer of dissolved carbon dioxide from the oceans to the atmosphere. This resulted in a large increase of the atmospheric carbon dioxide during the next 50,000 years, which is believed to have caused a temperature rise revealed by the oxygen-isotope data. The lowermost Tertiary sediments at site 524 include fossils with Cretaceous affinities, which may include both reworked individuals and some forms that survived for a while after the catastrophe. Our data indicate that many of the Cretaceous pelagic organisms became extinct over a period of a few tens of thousands of years, and do not contradict the scenario of cometary impact as a cause of mass mortality in the oceans, as suggested by an iridium anomaly at the Cretaceous-Tertiary boundary.
TL;DR: The assignment of the 1H nuclear magnetic resonance spectrum of glucagon bound to perdeuterated dodecylphosphocholine micelles with the use of two-dimensional 1Hnuclear magnetic resonance techniques provides a basis for the determination of the three-dimensional structure of lipid-bound glucagon.
TL;DR: In this paper, a method for the separation of coherent and incoherent magnetization transfer in two-dimensional NOE and chemical exchange spectroscopy is described, where the mixing time τ m is incremented systematically together with the evolution time t 1.
TL;DR: Two-dimensional NMR methods for correlating the spectra of abundant and dil. spins in solids are proposed in this paper, which simplify assignment and permit detn. of shielding tensors even when extensive overlaps occur.
TL;DR: One- and two-dimensional 1H-1H Overhauser experiments have now been used to obtain qualitative information on intramolecular proton-proton distances, showing that the N-terminal and the C-Terminal segments of melittin form two spatially distinct, compact domains.
TL;DR: Using steady state fluorescence anisotropy of diphenylhexatriene, it is shown that lipid peroxidation in rat liver microsomes increases the order of the microsomal phospholipid acyl chains, which might be due to the formation of covalent bonds between adjacent lipid radicals.
TL;DR: Differences between the 2 selected lines were not generally found in unstressed rats or in “high-stress” (ether, immobilisation, footshock) situations.
TL;DR: The rate of appearance of labelled sucrose in the vacuoles closely resembled the rate of sucrose synthesis in the protoplasts and the same was the case for malate and citrate.
TL;DR: In this article, the authors evaluated the utility of pre-column amino acid derivatization, liquid chromatographic separation and subsequent quantitation, and concluded that the results are significantly better at the lower picomole level, an area where few if any analyzers can perform routinely.
01 Jan 1982
TL;DR: In this article, the authors examined the problem of positivity in relation to the partial realization of scalar power series and proved an exact criterion for positivity for second-order realizations.
Abstract: This paper examines the problem of “positivity” in relation to the partial realization of scalar power series. An exact criterion of positivity is proved for second-order realizations. The general case is currently unsolved. Even the special results contained here show that the so-called “maximum entropy principle” cannot be applied to the realization problem in the naive sense in which it is employed by physicists. It would be better to call this principle a “prejudice” because it does not fully utilize the information inherent in the data and does not provide a realization with natural (“minimal”) mathematical properties.
TL;DR: A detailed and comprehensive description of column preparation techniques is presented in this paper, where a critical comparison of commercial with laboratory-mad columns has revealed important new facts, such as: whereas commercial columns are now preferentially made of fused silica, there are strong arguments for retaining glass for laboratory- mad capillary columns.
TL;DR: A liver plasma-membrane fraction capable of Ca2+ uptake was isolated and showed high Na+, K+-ATPase, low glucose-6 phosphatase activity, and transported alanine in a Na+-dependent fashion, suggesting the possibility of a H/Ca2+ exchange.
Abstract: A liver plasma-membrane fraction capable of Ca2+ uptake was isolated. The fraction exhibited high Na+, K+-ATPase, low glucose-6 phosphatase activity, and transported alanine in a Na+-dependent fashion. The uptake of Ca2+ was ATP-dependent; UTP, GTP, or CTP did not substitute for ATP. The presence of oxalate did not significantly alter the rate of uptake. The pH optimum of the reaction was basic (no uptake was visible at pH 6.8). These properties are at variance with those of the endoplasmic reticulum Ca2+ uptake system, which is oxalate-dependent, and has an acid pH optimum. The ATP-dependent Ca2+ uptake has a Km(Ca2+) of 1.4 X 10(-8) M and a Vmax of transport of 30 nmol X mg protein-1 X min-1. No conclusive results were obtained on the calmodulin-sensitivity of the process: addition of calmodulin to the vesicles did not stimulate uptake, and the anti-calmodulin drug trifluoperazine had no inhibitory effect. However, another anti-calmodulin drug (R24571) had a limited, but statistically significant, inhibitory action. A partial release of the accumulated Ca2+ from the vesicles could be induced by the addition of Na+, and incubation of the vesicles in a high Na+ medium (as compared to high K+ medium) resulted in lower (about 25%) calcium uptake. Partial release of the accumulated Ca2+ could be induced also by the addition of H+. The releasing effect of H+, taken together with the absence of Ca2+ uptake at acid pH, suggests the possibility of a H+/Ca2+ exchange.
TL;DR: In this paper, a construction scheduling technique is presented which is more advantageous than bar charts and network schedules, particularly for repetitive activities and for scheduling the work in sections of a project (floors, bridge spans, road and sewage sections).
Abstract: A construction scheduling technique is presented which is, in many cases, more advantageous than bar charts and network schedules, particularly for repetitive activities and for scheduling the work in sections of a project (floors, bridge spans, road and sewage sections, etc.). The technique is labeled the time space scheduling technique because it shows clearly the connections of activities, their duration times, and sections (space) where they take place in a given time. The principal organization of the construction process is described. Examples of the application of time space scheduling are given for the pump foundation in a pipeline, construction of an apartment house, a multistoried concrete building, a road section, and a railway bridge. The time space scheduling technique is compared to bar charts and network scheduling techniques. Advantages and limitations are examined.
TL;DR: In this paper, the authors measured the coagulation rate of small particles in a gas with radii of 3-16 nm and found that the results almost agree with the expectations based on bulk electronic properties.
Abstract: Dispersion forces enhance the coagulation rate of small particles in a gas. Measurements of coagulation rates on ultrafine Ag and C particles with radii of 3-16 nm were performed. The results obtained with C particles almost agree with the expectations based on bulk electronic properties. However, Ag particles 14 nm in radius exhibit a very large coagulation rate. It points to an enhancement of the dispersion forces of at least a factor of ${10}^{4}$.
TL;DR: In this paper, the authors investigate energy trapping in regular crystals of different dimensionalities, assuming a nearest-neighbor random walk of the excitation and quenching at first trap encounter.
TL;DR: The IHI system has four vibrationally bonded collinear bound states, which are located in the saddle point region of a minimum-free potential energy surface as mentioned in this paper, which is the same region of the IHI saddle point.
TL;DR: In the presence of tunicamycin yeast cells synthesize a carbohydrate-free carboxypeptidase Y, which could be traced after metabolic labeling with [ 14 C]-phenylalanine, which was segregated into the vacuoles to the same extent as the intact glycoprotein.