Immunoglobulin domains in Escherichia coli and other enterobacteria: from pathogenesis to applications in antibody technologies

The immunoglobulin (Ig) protein domain is widespread in nature having a well-recognized role in proteins of the immune system. In this review, we describe the proteins containing Ig-like domains in Escherichia coli and entero-bacteria, reporting their structural and functional properties, protein folding, and diverse biological roles. In addition, we cover the expression of heterolo-gous Ig domains in E. coli owing to its biotechnological application for expression and selection of antibody fragments and full-length IgG molecules. Ig-like domains in E. coli and enterobacteria are frequently found in cell surface proteins and fimbrial organelles playing important functions during host cell adhesion and invasion of pathogenic strains, being structural components of pilus and nonpilus fimbrial systems and members of the intimin/invasin family of outer membrane (OM) adhesins. Ig-like domains are also found in periplasmic chaperones and OM usher proteins assembling fimbriae, in oxidoreductases and hydrolytic enzymes, ATP-binding cassette transporters, sugar-binding and metal-resistance proteins. The folding of most E. coli Ig-like domains is assisted by periplasmic chaperones, peptidyl prolylcis/transisomerases and disulfide bond catalysts that also participate in the folding of antibodies expressed in this bacterium. The technologies for expression and selection of recombinant antibodies in E. coli are described along with their biotechnological potential.This work has been supported by Grants of the Spanish Ministry of Science and Innovation (BIO2008-05201; BIO2011-26689), the Autonomous Community of Madrid (S-BIO-236-2006; S2010-BMD-2312), CSIC (PIE 2011 20E049), ‘la Caixa’ Foundation, and the VI Framework Program from the European Union (FP6-LSHB-CT-2005-512061 NoE ‘EuroPathogenomics’).Peer reviewe

Edge-Magnetoplasmon Wave-Packet Revivals in the Quantum Hall Effect

The quantum Hall effect is necessarily accompanied by low-energy excitations localized at the edge of a two-dimensional electron system. For the case of electrons interacting via the long-range Coulomb interaction, these excitations are edge magnetoplasmons. We address the time evolution of localized edge-magnetoplasmon wave packets. On short times the wave packets move along the edge with classical E cross B drift. We show that on longer times the wave packets can have properties similar to those of the Rydberg wave packets that are produced in atoms using short-pulsed lasers. In particular, we show that edge-magnetoplasmon wave packets can exhibit periodic revivals in which a dispersed wave packet reassembles into a localized one. We propose the study of edge-magnetoplasmon wave packets as a tool to investigate dynamical properties of integer and fractional quantum-Hall edges. Various scenarios are discussed for preparing the initial wave packet and for detecting it at a later time. We comment on the importance of magnetoplasmon-phonon coupling and on quantum and thermal fluctuations.Comment: 18 pages, RevTex, 7 figures and 2 tables included, Fig. 5 was originally 3Mbyte and had to be bitmapped for submission to archive; in the process it acquired distracting artifacts, to upload the better version, see http://physics.indiana.edu/~uli/publ/projects.htm

Long-Term Evolution and Revival Structure of Rydberg Wave Packets for Hydrogen and Alkali-Metal Atoms

This paper begins with an examination of the revival structure and long-term evolution of Rydberg wave packets for hydrogen. We show that after the initial cycle of collapse and fractional/full revivals, which occurs on the time scale $t_{\rm rev}$, a new sequence of revivals begins. We find that the structure of the new revivals is different from that of the fractional revivals. The new revivals are characterized by periodicities in the motion of the wave packet with periods that are fractions of the revival time scale $t_{\rm rev}$. These long-term periodicities result in the autocorrelation function at times greater than $t_{\rm rev}$ having a self-similar resemblance to its structure for times less than $t_{\rm rev}$. The new sequence of revivals culminates with the formation of a single wave packet that more closely resembles the initial wave packet than does the full revival at time $t_{\rm rev}$, i.e., a superrevival forms. Explicit examples of the superrevival structure for both circular and radial wave packets are given. We then study wave packets in alkali-metal atoms, which are typically used in experiments. The behavior of these packets is affected by the presence of quantum defects that modify the hydrogenic revival time scales and periodicities. Their behavior can be treated analytically using supersymmetry-based quantum-defect theory. We illustrate our results for alkali-metal atoms with explicit examples of the revival structure for radial wave packets in rubidium.Comment: To appear in Physical Review A, vol. 51, June 199

Ice-algal carbon supports harp and ringed seal diets in the European Arctic: evidence from fatty acid and stable isotope markers

Sea-ice declines in the European Arctic have led to substantial changes in marine food webs. To better understand the biological implications of these changes, we quantified the contributions of ice-associated and pelagic carbon sources to the diets of Arctic harp and ringed seals using compound-specific stable isotope ratios of fatty acids in specific primary producer biomarkers derived from sea-ice algae and phytoplankton. Comparison of fatty acid patterns between these 2 seal species indicated clear dietary separation, while the compound-specific stable isotope ratios of the same fatty acids showed partial overlap. These findings suggest that harp and ringed seals target different prey sources, yet their prey rely on ice and pelagic primary production in similar ways. From Bayesian stable isotope mixing models, we estimated that relative contributions of sympagic and pelagic carbon in seal blubber was an average of 69% and 31% for harp seals, and 72% and 28% for ringed seals, respectively. The similarity in the Bayesian estimations also indicates overlapping carbon sourcing by these 2 species. Our findings demonstrate that the seasonal ice-associated carbon pathway contributes substantially to the diets of both harp and ringed seals

Quantum Defects and the Long-Term Behavior of Radial Rydberg Wave Packets

We show that a theoretical description of radial Rydberg wave packets in alkali-metal atoms based solely on hydrogenic wave functions and energies is insufficient to explain data that could be obtained in pump-probe experiments with current technology. The modifications to long-term revival times induced by quantum defects cannot be obtained by direct scaling of the hydrogenic results. Moreover, the effects of laser detuning and quantum defects are different. An alternative approach providing analytical predictions using supersymmetry-based quantum-defect theory is presented.Comment: IUHET 281, June 1994, to appear in Rapid Communications, Physical Review A (December 1994

Einstein-aether theory, violation of Lorentz invariance, and metric-affine gravity

We show that the Einstein-aether theory of Jacobson and Mattingly (J&M) can be understood in the framework of the metric-affine (gauge theory of) gravity (MAG). We achieve this by relating the aether vector field of J&M to certain post-Riemannian nonmetricity pieces contained in an independent linear connection of spacetime. Then, for the aether, a corresponding geometrical curvature-square Lagrangian with a massive piece can be formulated straightforwardly. We find an exact spherically symmetric solution of our model.Comment: Revtex4, 38 pages, 1 figur

The Bivariate Normal Copula

We collect well known and less known facts about the bivariate normal distribution and translate them into copula language. In addition, we prove a very general formula for the bivariate normal copula, we compute Gini's gamma, and we provide improved bounds and approximations on the diagonal.Comment: 24 page

The SpinBus Architecture: Scaling Spin Qubits with Electron Shuttling

Quantum processor architectures must enable scaling to large qubit numbers while providing two-dimensional qubit connectivity and exquisite operation fidelities. For microwave-controlled semiconductor spin qubits, dense arrays have made considerable progress, but are still limited in size by wiring fan-out and exhibit significant crosstalk between qubits. To overcome these limitations, we introduce the SpinBus architecture, which uses electron shuttling to connect qubits and features low operating frequencies and enhanced qubit coherence. Device simulations for all relevant operations in the Si/SiGe platform validate the feasibility with established semiconductor patterning technology and operation fidelities exceeding 99.9 %. Control using room temperature instruments can plausibly support at least 144 qubits, but much larger numbers are conceivable with cryogenic control circuits. Building on the theoretical feasibility of high-fidelity spin-coherent electron shuttling as key enabling factor, the SpinBus architecture may be the basis for a spin-based quantum processor that meets the scalability requirements for practical quantum computing.Comment: 15 pages, 9 figure

Cruise report DISCOL 3, SONNE cruise 77 : Cruise report DISCOL 3, Sonne cruise 77 : January 26 - February 27, 1992, Balboa/Panama-Balboa/Panama

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