Pi*-pi* bonding interactions generated by halogen oxidation of zirconium(IV) redox-active ligand complexes.

The new complex, [Zr(pda)2]n (1, pda2- = N,N'-bis(neo-pentyl)-ortho-phenylenediamide, n = 1 or 2), prepared by the reaction of 2 equiv of pdaLi2 with ZrCl4, reacts rapidly with halogen oxidants to afford the new product ZrX2(disq)2 (3, X = Cl, Br, I; disq- = N,N'-bis(neo-pentyl)-ortho-diiminosemiquinonate) in which each redox-active ligand has been oxidized by one electron. The oxidation products 3a-c have been structurally characterized and display an unusual parallel stacked arrangement of the disq- ligands in the solid state, with a separation of approximately 3 A. Density functional calculations show a bonding-type interaction between the SOMOs of the disq- ligands to form a unique HOMO while the antibonding linear combination forms a unique LUMO. This orbital configuration leads to a closed-shell-singlet ground-state electron configuration (S = 0). Temperature-dependent magnetism measurements indicate a low-lying triplet excited state at approximately 750 cm-1. In solution, 3a-c show strong disq--based absorption bands that are invariant across the halide series. Taken together these spectroscopic measurements provide experimental values for the one- and two-electron energies that characterize the pi-stacked bonding interaction between the two disq- ligands.

Résistances thérapeutiques dans les mouvements anormaux [Resistance to treatment in movement disorders].

Therapeutic strategies for essential tremor (ET) and Parkinson's disease (PD) can be divided into two successive steps, one based on oral medications and the other, more invasive, using pumps or functional neurosurgery. When ET becomes refractory to propranolol, primidone and other, second-choice compounds, deep brain stimulation of the VIM nucleus of the thalamus can be considered. When PD becomes resistant to dopamine replacement therapy using various combinations of dopaminergic agents, then three options can be discussed: first, a subcutaneous apomorphine mini-pump, second, a jejunal levodopa-delivery system by means of percutaneous gastrostomy, and third, bilateral deep brain stimulation of the subthalamic nucleus. The above interventions are successful in about 80% of cases.

Contrasting the functional properties of GABAergic axon terminals with single and multiple synapses in the thalamus

Diverse sources of GABAergic inhibition are a major feature of cortical networks, but distinct inhibitory input systems have not been systematically characterized in the thalamus. Here, we contrasted the properties of two independent GABAergic pathways in the posterior thalamic nucleus of rat, one input from the reticular thalamic nucleus (nRT), and one "extrareticular" input from the anterior pretectal nucleus (APT). The vast majority of nRT-thalamic terminals formed single synapses per postsynaptic target and innervated thin distal dendrites of relay cells. In contrast, single APT-thalamic terminals formed synaptic contacts exclusively via multiple, closely spaced synapses on thick relay cell dendrites. Quantal analysis demonstrated that the two inputs displayed comparable quantal amplitudes, release probabilities, and multiple release sites. The morphological and physiological data together indicated multiple, single-site contacts for nRT and multisite contacts for APT axons. The contrasting synaptic arrangements of the two pathways were paralleled by different short-term plasticities. The multisite APT-thalamic pathway showed larger charge transfer during 50-100 Hz stimulation compared with the nRT pathway and a greater persistent inhibition accruing during stimulation trains. Our results demonstrate that the two inhibitory systems are morpho-functionally distinct and suggest and that multisite GABAergic terminals are tailored for maintained synaptic inhibition even at high presynaptic firing rates. These data explain the efficacy of extrareticular inhibition in timing relay cell activity in sensory and motor thalamic nuclei. Finally, based on the classic nomenclature and the difference between reticular and extrareticular terminals, we define a novel, multisite GABAergic terminal type (F3) in the thalamus.

Molecular and functional characterization of a novel cardiac-specific human tropomyosin isoform.

BACKGROUND: Tropomyosin (TM), an essential actin-binding protein, is central to the control of calcium-regulated striated muscle contraction. Although TPM1alpha (also called alpha-TM) is the predominant TM isoform in human hearts, the precise TM isoform composition remains unclear. METHODS AND RESULTS: In this study, we quantified for the first time the levels of striated muscle TM isoforms in human heart, including a novel isoform called TPM1kappa. By developing a TPM1kappa-specific antibody, we found that the TPM1kappa protein is expressed and incorporated into organized myofibrils in hearts and that its level is increased in human dilated cardiomyopathy and heart failure. To investigate the role of TPM1kappa in sarcomeric function, we generated transgenic mice overexpressing cardiac-specific TPM1kappa. Incorporation of increased levels of TPM1kappa protein in myofilaments leads to dilated cardiomyopathy. Physiological alterations include decreased fractional shortening, systolic and diastolic dysfunction, and decreased myofilament calcium sensitivity with no change in maximum developed tension. Additional biophysical studies demonstrate less structural stability and weaker actin-binding affinity of TPM1kappa compared with TPM1alpha. CONCLUSIONS: This functional analysis of TPM1kappa provides a possible mechanism for the consequences of the TM isoform switch observed in dilated cardiomyopathy and heart failure patients.

SwissParam: a fast force field generation tool for small organic molecules.

The drug discovery process has been deeply transformed recently by the use of computational ligand-based or structure-based methods, helping the lead compounds identification and optimization, and finally the delivery of new drug candidates more quickly and at lower cost. Structure-based computational methods for drug discovery mainly involve ligand-protein docking and rapid binding free energy estimation, both of which require force field parameterization for many drug candidates. Here, we present a fast force field generation tool, called SwissParam, able to generate, for arbitrary small organic molecule, topologies, and parameters based on the Merck molecular force field, but in a functional form that is compatible with the CHARMM force field. Output files can be used with CHARMM or GROMACS. The topologies and parameters generated by SwissParam are used by the docking software EADock2 and EADock DSS to describe the small molecules to be docked, whereas the protein is described by the CHARMM force field, and allow them to reach success rates ranging from 56 to 78%. We have also developed a rapid binding free energy estimation approach, using SwissParam for ligands and CHARMM22/27 for proteins, which requires only a short minimization to reproduce the experimental binding free energy of 214 ligand-protein complexes involving 62 different proteins, with a standard error of 2.0 kcal mol(-1), and a correlation coefficient of 0.74. Together, these results demonstrate the relevance of using SwissParam topologies and parameters to describe small organic molecules in computer-aided drug design applications, together with a CHARMM22/27 description of the target protein. SwissParam is available free of charge for academic users at www.swissparam.ch.

Functional analysis of human POT1 and RPA : insights into the role of single stranded DNA binding proteins at telomeres

Abstract Telomeres, the natural ends of chromosomes, need to be protected from chromosome end fusions, aberrant homologous recombination and degradation. In humans, chromosome ends are specified through arrays of tandemly repeated 5'-TTAGGG-3' hexamers, ending in a 3' overhang. A complex formed by the six proteins TRF1, TRF2, hRap1, TIN2, TPP1 and POT1 specifically assocìates with and protects telomeres. Telomeres are maintained by semiconservative DNA replication and by a specialized reverse transcriptase, telomerase, that carries an RNA subunit which templates new telomeric repeat synthesis. The telomeric single stranded (ss) DNA binding protein POT1 protects the telomeric 3' overhang and modulates telomerase-mediated telomere elongation. It is possible that POT1 also influences DNA synthesis during semiconservative DNA replication, which is initiated by the DNA polymerase alpha-primase complex. The heterotrimeric ss DNA-binding protein RPA plays essential roles during DNA replication. RPA binds to ss DNA with high affinity in order to stabilize ss DNA and facilitate nascent strand synthesis at the replication fork. Here we investigate how the two proteins RPA and POT1 contribute to telomere maintenance by regulating semi-conservative DNA replication and telomerase. Using chromatin immunoprecipitation experiments, we show that RPA associates with telomeres during S-phase. Analysis of telomere structure in cells shRNA-depleted for RPA and POT1 reveals that loss of RPA and POT1 causes exposure of single-stranded DNA at telomeres, suggestive of incomplete DNA replication. Biochemical experiments using purified recombinant POT1 and RPA show that saturating telomeric oligonucleotides with POT1 or RPA reduces the primase activity of the DNA polymerase alpha-primase complex and the overall activity of telomerase. POT1 and RPA also increase the primer extension by DNA polymerase alpha-primase complex and the processivity of telomerase under certain conditions, although POT1 increases the activities to a greater extent than RPA. We propose that POT1 is required for proper replication of the lagging strand of telomeres and that some phenotypes observed in POT1-depleted cells may stern from incomplete DNA replication rather than de-protection of the single-stranded overhang. Résumé Les télomères, les extrémités normales des chromosomes linéaires, doivent être protégés des fusions chromosomiques, d'événements de recombinaison homologue aberrants et de phénomènes de dégradation. Chez l'Homme, les extrémités des chromosomes sont constitués d'ADN double brin répétitif de séquence 5'-TTAGGG-3', d'une extension simple brin 3' sortante et d'un complexe protéique formé des six facteurs TRF1, TRF2, hRap1, TIN2, TPP1 et POT1 qui, s'associant à cette séquence, protègent l'ADN télomèrique. Les télomères sont maintenus par la télomérase, une transcriptase inverse capable d'allonger l'extension 3' sortante télomérique. POT1 lie l'ADN simple brin télomérique et module l'élongation des télomères par la télomérase. POT1 pourrait en théorie également influencer la réplication semi-conservative de l'ADN. L'ADN-polymérase Pal alpha-primase amorce et initie la synthèse d'ADN. Pendant la réplication, l'ADN simple brin est stabilisé par RPA, un complexe hétérotrimèrique qui lie l'ADN simple brin. RPA facilite la synthèse du brin naissant à la fourche de réplication. Ici nous avons étudié comment ces deux protéines qui lient l'ADN simple brin, RPA et POT1, régulent la réplication des télomères par la télomérase et la machinerie classique de réplication de l'ADN. Par immunoprécipitation de chromatine (ChIP), nous montrons que RPA est localisé aux télomères lors de la phase S du cycle cellulaire. De plus, l'analyse de la structure des télomeres indique que !a perte de RPA ou de POT1 conduit à l'apparition d'ADN simple brin télomérique, suggérant une réplication incomplète de l'ADN télomérique in vivo. Par une approche complémentaire biochimique utilisant les protéines POT1 et RPA recombinantes purifiées, nous montrons également que la liaison de POT1 ou de RPA à des oligonucléotides télomériques bloque l'activité primase du complexe polymérase alpha/primase et réduit l'activité télomérase sur ces substrats. En revanche, leur liaison augmente l'activité ADN-polymérase du complexe polymérase alpha/primase, ainsi que fa processivité de la télomérase dans certaines conditions, POT1 étant le plus efficace des deux facteurs. Nous proposons que POT1 est nécessaire à la réplication du brin retardé au niveau des télomères, ce qui suggère que certains phénotypes des cellules déplétés en POT1 puissent résulter d'une réplication incomplète de l'ADN télémétrique plutôt que d'une déprotection de l'extrémité sortante des télomères.

Precursors of functional MHC class I- or class II-restricted CD8alphaalpha(+) T cells are positively selected in the thymus by agonist self-peptides.

The origin and specificity of alphabeta TCR(+) T cells that express CD8alphaalpha have been controversial issues. Here we provide direct evidence that precursors of functional CD8alphaalpha T cells are positively selected in the thymus in the presence of agonist self-peptides. Like conventional positive selection, this agonist selection process requires functional TCR alpha-CPM, whereas it is independent of CD8beta expression. Furthermore, CD8alphaalpha expression on mature, agonist-selected T cells does not imply selection by MHC class I, and CD8alphaalpha(+) T cells can be either class I or class II restricted. Our data define a distinct agonist-dependent, positive selection process in the thymus, and they suggest a function for CD8alphaalpha distinct from the conventional TCR coreceptor function of CD8alphabeta or CD4.

Electron microscopy of RecA-DNA complexes: Two different states, their functional significance and relation to the solved crystal structure

Seven different electron microscopy techniques habe been employed to study the RecA protein of E. coli. This review provides a summary of the conclusions that have been drawn from these studies, and attempts to relate these observations to models for the role of RecA protein in homologous recombination.

Functional Sub-Types

The paper argues that a functional reduction of ordinary psychology to neuropsychology is possible by means of constructing fine-grained functional, mental sub-types that are coextensive with neuropsychological types. We establish this claim by means of considering as examples the cases of the disconnection syndrome and schizophrenia. We point out that the result is a conservative reduction, vindicating the scientific quality of the mental types of ordinary psychology by systematically linking them with neuroscience. That procedure of conservative reduction by means of functional sub-types is in principle repeatable down to molecular neuroscience.

Identification of optimal structural connectivity using functional connectivity and neural modeling.

The complex network dynamics that arise from the interaction of the brain's structural and functional architectures give rise to mental function. Theoretical models demonstrate that the structure-function relation is maximal when the global network dynamics operate at a critical point of state transition. In the present work, we used a dynamic mean-field neural model to fit empirical structural connectivity (SC) and functional connectivity (FC) data acquired in humans and macaques and developed a new iterative-fitting algorithm to optimize the SC matrix based on the FC matrix. A dramatic improvement of the fitting of the matrices was obtained with the addition of a small number of anatomical links, particularly cross-hemispheric connections, and reweighting of existing connections. We suggest that the notion of a critical working point, where the structure-function interplay is maximal, may provide a new way to link behavior and cognition, and a new perspective to understand recovery of function in clinical conditions.

Correlates of frailty, prediction of functional decline and preventative approaches - selected results from the lausanne cohort 65+ (lc65+) study (Switzerland) (Lausanne) and the longitudinal urban cohort ageing study (Lucas) (Germany)

Overall introduction.- Longitudinal studies have been designed to investigate prospectively, from their beginning, the pathway leading from health to frailty and to disability. Knowledge about determinants of healthy ageing and health behaviour (resources) as well as risks of functional decline is required to propose appropriate preventative interventions. The functional status in older people is important considering clinical outcome in general, healthcare need and mortality. Part I.- Results and interventions from lucas (longitudinal urban cohort ageing study). Authors.- J. Anders, U. Dapp, L. Neumann, F. Pröfener, C. Minder, S. Golgert, A. Daubmann, K. Wegscheider,. W. von Renteln-Kruse Methods.- The LUCAS core project is a longitudinal cohort of urban community-dwelling people 60 years and older, recruited in 2000/2001. Further LUCAS projects are cross-sectional comparative and interventional studies (RCT). Results.- The emphasis will be on geriatric medical care in a population-based approach, discussing different forms of access, too. (Dapp et al. BMC Geriatrics 2012, 12:35; http://www.biomedcentral.com/1471-2318/12/35): - longitudinal data from the LUCAS urban cohort (n = 3.326) will be presented covering 10 years of observation, including the prediction of functional decline, need of nursing care, and mortality by using a self-filling screening tool; - interventions to prevent functional decline do focus on first (pre-clinical) signs of pre-frailty before entering the frailty-cascade ("Active Health Promotion in Old Age", "geriatric mobility centre") or disability ("home visits"). Conclusions.- The LUCAS research consortium was established to study particular aspects of functional competence, its changes with ageing, to detect pre-clinical signs of functional decline, and to address questions on how to maintain functional competence and to prevent adverse outcome in different settings. The multidimensional data base allows the exploration of several further questions. Gait performance was exmined by GAITRite®-System. Supported by the Federal Ministry for Education and Research (BMBF Funding No. 01ET1002A). Part II.- Selected results from the lausanne cohort 65+ (Lc65 + ) Study (Switzerland). Authors.- Prof Santos-Eggimann Brigitte, Dr Seematter-Bagnoud Laurence, Prof Büla Christophe, Dr Rochat Stéphane. Methods.- The Lc65+ cohort was launched in 2004 with the random selection of 3054 eligible individuals aged 65 to 70 (birth year 1934-1938) in the non-institutionalized population of Lausanne (Switzerland). Results.- Information is collected about life course social and health-related events, socio-economics, medical and psychosocial dimensions, lifestyle habits, limitations in activities of daily living, mobility impairments, and falls. Gait performance are objectively measured using body-fixed sensors. Frailty is assessed using Fried's frailty phenotype. Follow-up consists in annual self-completed questionnaires, as well as physical examination and physical and mental performance tests every three years. - Lausanne cohort 65+ (Lc65 + ): design and longitudinal outcomes. The baseline data collection was completed among 1422 participants in 2004-2005 through self-completed questionnaires, face-to-face interviews, physical examination and tests of mental and physical performances. Information about institutionalization, self-reported health services utilization, and death is also assessed. An additional random sample (n = 1525) of 65-70 years old subjects was recruited in 2009 (birth year 1939-1943). - lecture no 4: alcohol intake and gait parameters: prevalent and longitudinal association in the Lc65+ study. The association between alcohol intake and gait performance was investigated.

The functional neuroimaging correlates of psychogenic versus organic dystonia.

The neurobiological basis of psychogenic movement disorders remains poorly understood and the management of these conditions difficult. Functional neuroimaging studies have provided some insight into the pathophysiology of disorders implicating particularly the prefrontal cortex, but there are no studies on psychogenic dystonia, and comparisons with findings in organic counterparts are rare. To understand the pathophysiology of these disorders better, we compared the similarities and differences in functional neuroimaging of patients with psychogenic dystonia and genetically determined dystonia, and tested hypotheses on the role of the prefrontal cortex in functional neurological disorders. Patients with psychogenic (n = 6) or organic (n = 5, DYT1 gene mutation positive) dystonia of the right leg, and matched healthy control subjects (n = 6) underwent positron emission tomography of regional cerebral blood flow. Participants were studied during rest, during fixed posturing of the right leg and during paced ankle movements. Continuous surface electromyography and footplate manometry monitored task performance. Averaging regional cerebral blood flow across all tasks, the organic dystonia group showed abnormal increases in the primary motor cortex and thalamus compared with controls, with decreases in the cerebellum. In contrast, the psychogenic dystonia group showed the opposite pattern, with abnormally increased blood flow in the cerebellum and basal ganglia, with decreases in the primary motor cortex. Comparing organic dystonia with psychogenic dystonia revealed significantly greater regional blood flow in the primary motor cortex, whereas psychogenic dystonia was associated with significantly greater blood flow in the cerebellum and basal ganglia (all P < 0.05, family-wise whole-brain corrected). Group × task interactions were also examined. During movement, compared with rest, there was abnormal activation in the right dorsolateral prefrontal cortex that was common to both organic and psychogenic dystonia groups (compared with control subjects, P < 0.05, family-wise small-volume correction). These data show a cortical-subcortical differentiation between organic and psychogenic dystonia in terms of regional blood flow, both at rest and during active motor tasks. The pathological prefrontal cortical activation was confirmed in, but was not specific to, psychogenic dystonia. This suggests that psychogenic and organic dystonia have different cortical and subcortical pathophysiology, while a derangement in mechanisms of motor attention may be a feature of both conditions.

Architectural and Functional Similarities between Trimeric ATP-Gated P2X Receptors and Acid-Sensing Ion Channels

ATP-gated P2X receptors and acid-sensing ion channels are two distinct ligand-gated ion channels that assemble into trimers. They are involved in many important physiological functions such as pain sensation and are recognized as important therapeutic targets. They have unrelated primary structures and respond to different ligands (ATP and protons) and are thus considered as two different ion channels. As a consequence, comparisons of the biophysical properties and underlying mechanisms have only been rarely made between these two channels. However, the recent determination of their molecular structures by X-ray crystallography has revealed unexpected parallels in the architecture of the two pores, providing a basis for possible functional analogies. In this review, we analyze the structural and functional similarities that are shared by these trimeric ion channels, and we outline key unanswered questions that, if addressed experimentally, may help us to elucidate how two unrelated ion channels have adopted a similar fold of the pore.