Liebe am Nachmittag ­ Über dialogische Liebe und Verrat.

How easy should we take love? Does love call for exclusivity? Romantic non-exclusivity is widespread. One form thereof is the attempt to combine two or more loving relationships like modules that have nothing to do with each other. Bernard Schlink's short story «The night in Baden-Baden¼ beautifully exemplifies this modular kind of love. My main claim is that this form of romantic non-exclusivity amounts to betrayal and is therefore unethical. I argue for this claim on the basis of a dialogical understanding of love.

Albumin in patients with liver disease shows an altered conformation.

Human serum albumin (HSA) constitutes the primary transporter of fatty acids, bilirubin, and other plasma compounds. The binding, transport, and release of its cargos strongly depend on albumin conformation, which is affected by bound ligands induced by physiological and pathological conditions. HSA is both highly oxidized and heavily loaded with fatty acids and bilirubin in chronic liver disease. By employing small-angle X-ray scattering we show that HSA from the plasma of chronic liver disease patients undergoes a distinct opening compared to healthy donors. The extent of HSA opening correlates with clinically relevant variables, such as the model of end-stage liver disease score, bilirubin, and fatty acid levels. Although the mild oxidation of HSA in vitro does not alter overall structure, the alteration of patients' HSA correlates with its redox state. This study connects clinical data with structural visualization of albumin dynamicity in solution and underlines the functional importance of albumin's inherent flexibility.

The anticoagulant effects of ethyl pyruvate in whole blood samples.

BACKGROUND: Ethyl pyruvate (EP), the ethyl ester of pyruvate, has proven antiinflammatory and antioxidative properties. Additionally, anticoagulant properties have been suggested recently. EP, therefore, is a potentially antiatherosclerotic drug. We aimed to investigate whether EP possesses antiplatelet and anticoagulant properties particularly in the physiological environment of whole blood. METHODS: We investigated the effects of increasing concentrations of EP on platelet function, on the course of clot development, and on standard coagulation times. Additionally, clot ultrastructure using scanning electron microscopy was analysed. RESULTS: EP exerted significant antiplatelet actions: i) Impedance aggregometry amplitudes (11.7 ± 3.0 ohm, 0 µg/mL EP) dose dependently decreased (7.8 ± 3.1 ohm, 1000 µg/mL EP; -33.3%). ATP exocytosis (0.87 ± 0.24 nM, 0 µg/mL EP) measured by the luminiscent method dose-dependently decreased (0.56 ± 0.14 nM, 1000 µg/mL; -35.6%). ii) Closure times (104.4 ± 23.8 s, 0 µg/mL EP) using the Platelet function analyzer were dose-dependently prolonged (180.5 ± 82.5 s, 1000 µg/mL EP; +72.9%) using membranes coated with collagen/ADP. iii) Surface coverage (15.9 ± 5.1%, 0 µg/mL EP) dose-dependently decreased (9.0 ± 3.7%, 1000 µg/mL EP; -43.4%) using the Cone and Platelet analyzer. EP also exerted significant anticoagulant actions: Coagulation times (177.9 ± 37.8, 0 µg/mL EP) evaluated by means of thrombelastometry were dose-dependently prolonged (212.8 ± 57.7 s, 1000 µg/mL EP; +19.6%). Activated partial thromboplastin times (31.5 ± 1.8 s, 0 µg/mL EP) were dose-dependently prolonged (35.6 ± 2.3 s, 1000 µg/mL EP; +13.0%). Prothrombin times (0.94 ± 0.02 INR, 0 µg/mL EP) were dose-dependently prolonged (1.09 ± 0.04 INR, 1000 µg/mL EP; +16.0%). CONCLUSION: We found that EP possesses antiplatelet and anticoagulant properties in whole blood. Together with its proven anti-inflammatory and antioxidative properties, EP is a potentially antiatherogenic drug.

The unique role of the agent within the romantic group.

In this commentary, we apply the authors' view to small groups consisting of two people who are in a committed romantic relationship. Our focus is on the circumstances that make it more likely that people will stay within such a group and minimize the chances that they will replace their partner. In our restless society, such ongoing replacement is a pressing issue.

Alterations in the ankyrin domain of TRPV4 cause congenital distal SMA, scapuloperoneal SMA and HMSN2C.

Spinal muscular atrophies (SMA, also known as hereditary motor neuropathies) and hereditary motor and sensory neuropathies (HMSN) are clinically and genetically heterogeneous disorders of the peripheral nervous system. Here we report that mutations in the TRPV4 gene cause congenital distal SMA, scapuloperoneal SMA, HMSN 2C. We identified three missense substitutions (R269H, R315W and R316C) affecting the intracellular N-terminal ankyrin domain of the TRPV4 ion channel in five families. Expression of mutant TRPV4 constructs in cells from the HeLa line revealed diminished surface localization of mutant proteins. In addition, TRPV4-regulated Ca(2+) influx was substantially reduced even after stimulation with 4alphaPDD, a TRPV4 channel-specific agonist, and with hypo-osmotic solution. In summary, we describe a new hereditary channelopathy caused by mutations in TRPV4 and present evidence that the resulting substitutions in the N-terminal ankyrin domain affect channel maturation, leading to reduced surface expression of functional TRPV4 channels.

Structural rearrangements in tubulin following microtubule formation.

Microtubules are essential cytoskeletal structures that mediate several dynamic processes in a cell. To shed light on the structural processes relating to microtubule formation and dynamic instability, we investigated microtubules composed of 15 protofilaments using cryo-electron microscopy, helical image reconstruction and computational modelling. Analysis of the configuration of the alpha beta-tubulin heterodimer shows distinct structural differences in both subunits, and illustrates that the tubulin subunits have different roles in the microtubule lattice. Our modelling data suggest that after GTP hydrolysis microtubules, adopt a conformational state somewhere between a straight protofilament conformation--as found in zinc-induced tubulin sheets--and an outward curved conformation--as found in tubulin-stathmin complexes. The tendency towards a curved conformation seems to be mediated mostly by beta-tubulin, whereas alpha-tubulin resembles a state more related to the straight structure. Our data suggest a possible explanation of dynamic instability of microtubules, and for nucleotide-sensitive microtubule-binding properties of microtubule-associated proteins and molecular motors.

Small angle X-ray scattering studies and modeling of Eudistylia vancouverii chlorocruorin and Macrobdella decora hemoglobin.

Annelids possess giant extracellular oxygen carriers that exhibit a hexagonal bilayer appearance and have molecular masses of approximately 3.5 MDa. By small angle x-ray scattering (SAXS), Eudistylia vancouverii chlorocruorin and Macrobdella decora hemoglobin were investigated in solution. On the basis of the experimental SAXS data, three-dimensional models were established in a two-step approach (trial and error and averaging). The main differences between the complexes concern the structure of their central part and the subunit architecture. Usage of our SAXS models as templates for automated model generation (program DAMMIN) led to refined models that fit perfectly the experimental data. Special attention was paid to the inhomogeneous density distribution observed within the complexes. DAMMIN models without a priori information could not reproducibly locate low-density areas. The usage of templates, however, improved the results considerably, in particular by applying electron microscopy-based templates. Biologically relevant information on the presence of low-density areas and hints for their presumable location could be drawn from SAXS and sophisticated modeling approaches. Provided that different models are analyzed carefully, this obviously opens a way to gain additional biologically relevant structural information from SAXS data.

A structural analysis of the interaction between ncd tail and tubulin protofilaments.

ncd is a minus-end directed, kinesin-like motor, which binds to microtubules with its motor domain and its cargo domain as well. Typical of retrograde motors, the motor domain of ncd locates to the C-terminal end of the polypeptide chain, and hence, the cargo domain constitutes the N-terminal region. To date, several studies have investigated the interaction properties of the motor domain with microtubules, but very few structural data are available about the tail itself or its interaction with microtubules as cargo. Here, we applied cryo-electron microscopy and helical 3D image reconstruction to 15 protofilament microtubules decorated with an ncd tail fragment (N-terminal residues 83-187, named NT6). In our study, the ncd tail shows a behaviour resembling filamentous MAPs such as tau protein, exhibiting a highly flexible structure with no large globular domains. NT6 binds to four different sites on the outer side of microtubules within the proximity of the kinesin motor-binding site. Two of these sites locate within the groove between two neighbouring protofilaments, and appear as strong binding sites, while the other two sites, located at the outer rim, appear to play a secondary role. In addition, the ncd tail fragment induces the formation of large protofilament sheets, suggesting a tail-induced modification of lateral protofilament contacts.

The three-dimensional structure of bovine rhodopsin determined by electron cryomicroscopy.

G-protein-coupled receptors are integral membrane proteins that respond to environmental signals and initiate signal transduction pathways, which activate cellular processes. Rhodopsin, a well known member of the G-protein-coupled receptor family, is located in the disk membranes of the rod outer segment, where it is responsible for the visualization of dim light. Rhodopsin is the most extensively studied G-protein-coupled receptor, and knowledge about its structure serves as a template for other related receptors. We have gained detailed structural knowledge from the crystal structure (1), which was solved by x-ray crystallography in 2000 using three-dimensional crystals. Here we report a three-dimensional density map of bovine rhodopsin determined by electron cryomicroscopy of two-dimensional crystals with p22(1)2(1) symmetry. The usage of relatively small and disordered crystals made the process of structure determination challenging. Special attention was paid to the extraction of amplitudes and phases, since usable raw data were limited to a maximum tilt of 45 degrees. In the refinement process, an improved unbending procedure was applied. This led to a final resolution of 5.5 A in the membrane plane and approximately 13 A perpendicular to it, making our electron density map the most accurate map of a G-protein-coupled receptor currently available by electron microscopy. Most important is the information we gain about the center of the membrane plane and the orientation of the molecule relative to the bilayer. This information cannot be retrieved from the three-dimensional crystals. In our electron density map, all seven transmembrane helices were identified, and their arrangement is in agreement with the arrangement known from the crystal structure (1). In the retinal binding pocket, a density peak adjacent to helix 3 suggests the position of the beta-ionine ring of the chromophore, and in its vicinity several of the bigger amino acids can be identified.

Visualisation of the actin cytoskeleton by cryo-electron microscopy.

An understanding of the mechanisms driving cell motility requires clarification of the structural organisation of actin filament arrays in the regions of cell protrusion termed lamellipodia. Currently, there is a lack of consensus on lamellipodia organisation stemming from the application of alternative procedures for ultrastructural visualisation of cytoskeleton networks. In this study, we show that cryo-electron microscopy of extracted cytoskeletons embedded in a thin layer of vitreous ice can reveal the organisation of cytoskeletal elements at high resolution. Since this method involves no dehydration, drying and contrasting steps that can potentially introduce subtle distortions of filament order and interactions, its application opens the way to resolving the controversial details of lamellipodia architecture.