University of Konstanz

About: University of Konstanz is a education organization based out in Konstanz, Baden-Württemberg, Germany. It is known for research contribution in the topics: Population & Membrane. The organization has 12115 authors who have published 27401 publications receiving 951162 citations. The organization is also known as: University of Constance & Universität Konstanz.

The time course of cortical facilitation during cued shifts of spatial attention.

Abstract: Adaptive behavior requires the rapid switching of attention among potentially relevant stimuli that appear in the environment. The present study used an electrophysiological approach to continuously measure the time course of visual pathway facilitation in human subjects as attention was shifted from one location to another. Steady-state visual evoked potentials (SSVEPs) were recorded to rapidly flickering lights at attended and unattended locations, and variations in SSVEP amplitude over time were calculated after a cue to shift attention. The build-up of cortical facilitation reflected in SSVEP amplitude was found to bear a close temporal relationship with the emergence of accurate target discriminations at the newly attended location.

Crystal structure of human β2‐glycoprotein I: implications for phospholipid binding and the antiphospholipid syndrome

Abstract: The high affinity of human plasma beta2-glycoprotein I (beta(2)GPI), also known as apolipoprotein-H (ApoH), for negatively charged phospholipids determines its implication in a variety of physiological pathways, including blood coagulation and the immune response. beta(2)GPI is considered to be a cofactor for the binding of serum autoantibodies from antiphospholipid syndrome (APS) and correlated with thrombosis, lupus erythematosus and recurrent fetal loss. We solved the beta(2)GPI structure from a crystal form with 84% solvent and present a model containing all 326 amino acid residues and four glycans. The structure reveals four complement control protein modules and a distinctly folding fifth C-terminal domain arranged like beads on a string to form an elongated J-shaped molecule. Domain V folds into a central beta-spiral of four antiparallel beta-sheets with two small helices and an extended C-terminal loop region. It carries a distinct positive charge and the sequence motif CKNKEKKC close to the hydrophobic loop composed of residues LAFW (313-316), resulting in an excellent counterpart for interactions with negatively charged amphiphilic substances. The beta(2)GPI structure reveals potential autoantibody-binding sites and supports mutagenesis studies where Trp316 and CKNKEKKC have been found to be essential for the phospholipid-binding capacity of beta(2)GPI.

Efficient generation of large random networks.

Abstract: Random networks are frequently generated, for example, to investigate the effects of model parameters on network properties or to test the performance of algorithms. Recent interest in the statistics of large-scale networks sparked a growing demand for network generators that can generate large numbers of large networks quickly. We here present simple and efficient algorithms to randomly generate networks according to the most commonly used models. Their running time and space requirement is linear in the size of the network generated, and they are easily implemented.

Transport mechanism of hydrophobic ions through lipid bilayer membranes.

Abstract: Evidence is presented that the transport of lipid-soluble ions through bilayer membranes occurs in three distinct steps: (1) adsorption to the membranesolution interface; (2) passage over an activation barrier to the opposite interface; and (3) desorption into the aqueous solution Support for this mechanism comes from a consideration of the potential energy of the ion, which has a minimum in the interface The formal analysis of the model shows that the rate constants of the individual transport steps can be determined from the relaxation of the electric current after a sudden change in the voltage Such relaxation experiments have been carried out with dipicrylamine and tetraphenylborate as permeable ions In both cases the rate-determining step is the jump from the adsorption site into the aqueous phase Furthermore, it has been found that with increasing ion concentration the membrane conductance goes through a maximum In accordance with the model recently developed by L J Bruner, this behavior is explained by a saturation of the interface, which leads to a blocking of the conductance at high concentrations

Ion selectivity of gram-negative bacterial porins.

Abstract: Twelve different porins from the gram-negative bacteria Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, and Yersinia pestis were reconstituted into lipid bilayer membranes. Most of the porins, except outer membrane protein P, formed large, water-filled, ion-permeable channels with a single-channel conductance between 1.5 and 6 nS in 1 M KCl. The ions used for probing the pore structure had the same relative mobilities while moving through the porin pore as they did while moving in free solution. Thus the single-channel conductances of the individual porins could be used to estimate the effective channel diameters of these porins, yielding values ranging from 1.0 to 2.0 nm. Zero-current potential measurements in the presence of salt gradients across lipid bilayer membranes containing individual porins gave results that were consistent with the conclusions drawn from the single-channel experiments. For all porins except protein P, the channels exhibited a greater cation selectivity for less mobile anions and a greater anion selectivity for less mobile cations, which again indicated that the ions were moving inside the pores in a fashion similar to their movement in the aqueous phase. Three porins, PhoE and NmpC of E. coli and protein P of P. aeruginosa, formed anion-selective pores. PhoE and NmpC were only weakly anion selective, and their selectivity was dependent on the mobility of the ions. In contrast, cations were unable to enter the selectivity filter of the protein P channel. This resulted in a high anion selectivity for all salts tested in this study. The other porins examined, including all of the known constitutive porins of the four gram-negative bacteria studied, were cation selective with a 3- to 40-fold preference for K+ ions over Cl- ions.