Structure of symmetric and asymmetric "ripple" phases in lipid bilayers

We reproduce the symmetric and asymmetric ``rippled'' $P_{\beta'}$ states of lipid membranes by Monte Carlo simulations of a coarse-grained molecular model for lipid-solvent mixtures. The structure and properties compare favorably with experiments. The asymmetric ripple state is characterized by a periodic array of fully interdigitated ``defect'' lines. The symmetric ripple state maintains a bilayer structure, but is otherwise structurally similar. The formation of both ripple states is driven by the propensity of lipid molecules with large head groups to exhibit splay.Comment: 4 pages, 4 figure

Beam test of ALPIDE Sensor

The Alice Pixel Detector (ALPIDE) is developed for the upgrade of the Inner Tracking System of the ALICE experiment at CERN, which will take place during second Long Shutdown in 2019-2020. ALPIDE is a Monolithic Active Pixel Sensor (MAPS), manufactured in a 180 nm CMOS Imaging Process of TowerJazz. Forecoming tracking detectors, based on this technology, will see strong advantages with the application of these sensors as they provide the highest capabilities in spatial resolution and utmost potential for being thin. In this work, the results of the ALPIDE sensor beam test, which took place at the Beam Test Facility of Laboratori Nazionali di Frascati, are presented

A swollen phase observed between the liquid-crystalline phase and the interdigitated phase induced by pressure and/or adding ethanol in DPPC aqueous solution

A swollen phase, in which the mean repeat distance of lipid bilayers is larger than the other phases, is found between the liquid-crystalline phase and the interdigitated gel phase in DPPC aqueous solution. Temperature, pressure and ethanol concentration dependences of the structure were investigated by small-angle neutron scattering, and a bending rigidity of lipid bilayers was by neutron spin echo. The nature of the swollen phase is similar to the anomalous swelling reported previously. However, the temperature dependence of the mean repeat distance and the bending rigidity of lipid bilayers are different. This phase could be a precursor to the interdigitated gel phase induced by pressure and/or adding ethanol.Comment: 7 pages, 6 figure

Sterols sense swelling in lipid bilayers

In the mimetic membrane system of phosphatidylcholine bilayers, thickening (pre-critical behavior, anomalous swelling) of the bilayers is observed, in the vicinity of the main transition, which is non-linear with temperature. The sterols cholesterol and androsten are used as sensors in a time-resolved simultaneous small- and wide angle x-ray diffraction study to investigate the cause of the thickening. We observe precritical behavior in the pure lipid system, as well as with sterol concentrations less than 15%. To describe the precritical behavior we introduce a theory of precritical phenomena.The good temperature resolution of the data shows that a theory of the influence of fluctuations needs modification. The main cause of the critical behavior appears to be a changing hydration of the bilayer.Comment: 11 pages, 7 ps figures included, to appear in Phys.Rev.

Echoic memory of a single pure tone indexed by change-related brain activity

<p>Abstract</p> <p>Background</p> <p>The rapid detection of sensory change is important to survival. The process should relate closely to memory since it requires that the brain separate a new stimulus from an ongoing background or past event. Given that sensory memory monitors current sensory status and works to pick-up changes in real-time, any change detected by this system should evoke a change-related cortical response. To test this hypothesis, we examined whether the single presentation of a sound is enough to elicit a change-related cortical response, and therefore, shape a memory trace enough to separate a subsequent stimulus.</p> <p>Results</p> <p>Under a paradigm where two pure sounds 300 ms in duration and 800 or 840 Hz in frequency were presented in a specific order at an even probability, cortical responses to each sound were measured with magnetoencephalograms. Sounds were grouped to five events regardless of their frequency, 1D, 2D, and 3D (a sound preceded by one, two, or three different sounds), and 1S and 2S (a sound preceded by one or two same sounds). Whereas activation in the planum temporale did not differ among events, activation in the superior temporal gyrus (STG) was clearly greater for the different events (1D, 2D, 3D) than the same event (1S and 2S).</p> <p>Conclusions</p> <p>One presentation of a sound is enough to shape a memory trace for comparison with a subsequent physically different sound and elicits change-related cortical responses in the STG. The STG works as a real-time sensory gate open to a new event.</p

Identification and Characterization of NF-Y Transcription Factor Families in the Monocot Model Plant Brachypodium distachyon

BACKGROUND: Nuclear Factor Y (NF-Y) is a heterotrimeric transcription factor composed of NF-YA, NF-YB and NF-YC proteins. Using the dicot plant model system Arabidopsis thaliana (Arabidopsis), NF-Y were previously shown to control a variety of agronomically important traits, including drought tolerance, flowering time, and seed development. The aim of the current research was to identify and characterize NF-Y families in the emerging monocot model plant Brachypodium distachyon (Brachypodium) with the long term goal of assisting in the translation of known dicot NF-Y functions to the grasses. METHODOLOGY/PRINCIPAL FINDINGS: We identified, annotated, and further characterized 7 NF-YA, 17 NF-YB, and 12 NF-YC proteins in Brachypodium (BdNF-Y). By examining phylogenetic relationships, orthology predictions, and tissue-specific expression patterns for all 36 BdNF-Y, we proposed numerous examples of likely functional conservation between dicots and monocots. To test one of these orthology predictions, we demonstrated that a BdNF-YB with predicted orthology to Arabidopsis floral-promoting NF-Y proteins can rescue a late flowering Arabidopsis mutant. CONCLUSIONS/SIGNIFICANCE: The Brachypodium genome encodes a similar complement of NF-Y to other sequenced angiosperms. Information regarding NF-Y phylogenetic relationships, predicted orthologies, and expression patterns can facilitate their study in the grasses. The current data serves as an entry point for translating many NF-Y functions from dicots to the genetically tractable monocot model system Brachypodium. In turn, studies of NF-Y function in Brachypodium promise to be more readily translatable to the agriculturally important grasses

Transcriptional Regulation of N-Acetylglutamate Synthase

The urea cycle converts toxic ammonia to urea within the liver of mammals. At least 6 enzymes are required for ureagenesis, which correlates with dietary protein intake. The transcription of urea cycle genes is, at least in part, regulated by glucocorticoid and glucagon hormone signaling pathways. N-acetylglutamate synthase (NAGS) produces a unique cofactor, N-acetylglutamate (NAG), that is essential for the catalytic function of the first and rate-limiting enzyme of ureagenesis, carbamyl phosphate synthetase 1 (CPS1). However, despite the important role of NAGS in ammonia removal, little is known about the mechanisms of its regulation. We identified two regions of high conservation upstream of the translation start of the NAGS gene. Reporter assays confirmed that these regions represent promoter and enhancer and that the enhancer is tissue specific. Within the promoter, we identified multiple transcription start sites that differed between liver and small intestine. Several transcription factor binding motifs were conserved within the promoter and enhancer regions while a TATA-box motif was absent. DNA-protein pull-down assays and chromatin immunoprecipitation confirmed binding of Sp1 and CREB, but not C/EBP in the promoter and HNF-1 and NF-Y, but not SMAD3 or AP-2 in the enhancer. The functional importance of these motifs was demonstrated by decreased transcription of reporter constructs following mutagenesis of each motif. The presented data strongly suggest that Sp1, CREB, HNF-1, and NF-Y, that are known to be responsive to hormones and diet, regulate NAGS transcription. This provides molecular mechanism of regulation of ureagenesis in response to hormonal and dietary changes

Nck adapter proteins: functional versatility in T cells

Nck is a ubiquitously expressed adapter protein that is almost exclusively built of one SH2 domain and three SH3 domains. The two isoproteins of Nck are functionally redundant in many aspects and differ in only few amino acids that are mostly located in the linker regions between the interaction modules. Nck proteins connect receptor and non-receptor tyrosine kinases to the machinery of actin reorganisation. Thereby, Nck regulates activation-dependent processes during cell polarisation and migration and plays a crucial role in the signal transduction of a variety of receptors including for instance PDGF-, HGF-, VEGF- and Ephrin receptors. In most cases, the SH2 domain mediates binding to the phosphorylated receptor or associated phosphoproteins, while SH3 domain interactions lead to the formation of larger protein complexes. In T lymphocytes, Nck plays a pivotal role in the T cell receptor (TCR)-induced reorganisation of the actin cytoskeleton and the formation of the immunological synapse. However, in this context, two different mechanisms and adapter complexes are discussed. In the first scenario, dependent on an activation-induced conformational change in the CD3ε subunits, a direct binding of Nck to components of the TCR/CD3 complex was shown. In the second scenario, Nck is recruited to the TCR complex via phosphorylated Slp76, another central constituent of the membrane proximal activation complex. Over the past years, a large number of putative Nck interactors have been identified in different cellular systems that point to diverse additional functions of the adapter protein, e.g. in the control of gene expression and proliferation