The origin of high-resolution IETS-STM images of organic molecules with functionalized tips

Recently, the family of high-resolution scanning probe imaging techniques using decorated tips has been complimented by a method based on inelastic electron tunneling spectroscopy (IETS). The new technique resolves the inner structure of organic molecules by mapping the vibrational energy of a single carbonmonoxide (CO) molecule positioned at the apex of a scanning tunnelling microscope (STM) tip. Here, we explain high-resolution IETS imaging by extending the model developed earlier for STM and atomic force microscopy (AFM) imaging with decorated tips. In particular, we show that the tip decorated with CO acts as a nanoscale sensor that changes the energy of the CO frustrated translation in response to the change of the local curvature of the surface potential. In addition, we show that high resolution AFM, STM and IETS-STM images can deliver information about intramolecular charge transfer for molecules deposited on a~surface. To demonstrate this, we extended our numerical model by taking into the account the electrostatic force acting between the decorated tip and surface Hartree potential.Comment: 5 pages, 4 figure

The mechanism of high-resolution STM/AFM imaging with functionalized tips

High resolution Atomic Force Microscopy (AFM) and Scanning Tunnelling Microscopy (STM) imaging with functionalized tips is well established, but a detailed understanding of the imaging mechanism is still missing. We present a numerical STM/AFM model, which takes into account the relaxation of the probe due to the tip-sample interaction. We demonstrate that the model is able to reproduce very well not only the experimental intra- and intermolecular contrasts, but also their evolution upon tip approach. At close distances, the simulations unveil a significant probe particle relaxation towards local minima of the interaction potential. This effect is responsible for the sharp sub-molecular resolution observed in AFM/STM experiments. In addition, we demonstrate that sharp apparent intermolecular bonds should not be interpreted as true hydrogen bonds, in the sense of representing areas of increased electron density. Instead they represent the ridge between two minima of the potential energy landscape due to neighbouring atoms

Funktionelle Charakterisierung der gamma-Sekretasekomponente PEN-2

Die gamma-Sekretase ist ein Proteasekomplex, der aus vier Komponenten, Presenilin (PS), Nicastrin (NCT), APH-1 und PEN-2, besteht und der die intramembranöse Prozessierung verschiedener Typ I Transmembranproteine, einschliesslich des Alzheimer-assoziierten beta-Amyloid Vorläuferproteins, katalysiert. In der vorliegenden Arbeit wurden stabile PEN-2 RNAi-Knockdown Zellen (PEN-2KD) dazu verwendet, um Hinweise auf die Funktion von PEN-2 bei der Assemblierung und Reifung des gamma-Sekretasekomplexes, die Rolle von PEN-2 im aktiven Komplex und für die gamma-Sekretaseaktivität zu erhalten. Zusätzlich wurden, vor dem Hintergrund des PEN-2KD, RNAi-resistente PEN-2 Varianten analysiert, die in einer Struktur- /Funktionsanalyse auf ihre Fähigkeit hin untersucht wurden, den Defekt des PEN- 2KD aufzuheben, um damit funktionell wichtige Domänen im PEN-2 Protein zu identifizieren. Der Knockdown von PEN-2 war mit gestörter Reifung von NCT und blockierter PS Endoproteolyse assoziiert. PS akkumulierte als Vollängenprotein (PSholo), das durch Komplexbildung mit NCT und APH-1 stabilisiert wurde. In Abwesenheit von PEN-2 können PS, NCT und APH-1 zu einem trimeren Komplex assemblieren, PEN- 2 ist danach allerdings notwendig, um die Reifung des gamma-Sekretasekomplexes durch Initialisierung der PS Endoproteolyse einzuleiten. Interessanterweise bewirkte der Knockdown von PEN-2 auch in Endoproteolyse defizienten SwAPP/PS1 deltaExon9 Zellen einen Defekt in der Reifung von NCT. Dies schlägt eine generelle Rolle von PEN-2 bei der Reifung und für die Aktivität der gamma-Sekretase vor, die unabhängig von der PS Endoproteolyse ist. Die Defekte des PEN-2KD konnten effektiv durch RNAi-resistentes wt-PEN-2 revertiert werden. In der folgenden Struktur-/Funktionsanalyse erwies sich am N-Terminus mit einem Epitop-tag verlängertes PEN-2 als voll funktionell, wohingegen sowohl die Verlängerung des C-Terminus mit einem tag, als auch eine Trunkierung des C-Terminus (PEN-2 deltaC) defekte PEN-2 Varianten hervorrief. Diese konnten zwar die Akkumulation von PSholo, die mit dem Knockdown von PEN-2 assoziiert war ausgleichen, konnten aber weder normale Spiegel an PS-NTF und -CTF herstellen, noch für eine Reifung von NCT sorgen. PEN-2 deltaC war sehr instabil und wurde schnell vom Proteasom abgebaut, was mit der Unfähigkeit einen stabilen gamma-Sekretasekomplex zu bilden konsistent war. Zusätzlich verursachte die Expression von PEN-2 deltaC eine selektive Instabilität des PS-NTF/-CTF Heterodimers, das ebenfalls vom Proteasom abgebaut wurde, wohingegen NCT und APH-1 stabil blieben. Der C-Terminus von PEN-2 ist nicht für die Einleitung der PS Endoproteolyse notwendig. Danach wird er allerdings benötigt um die entstandenen PS Fragmente und PEN-2 selbst im Komplexzu stabilisieren. Um den PEN-2 C-Terminus genauer zu untersuchen, wurden unterschiedliche Deletionen und Mutationen mehrerer konservierter Aminosäuren, im PEN-2KD auf funktionelle Aktivität hin analysiert. Progressive Verkürzung des C-Terminus bewirkte einen zunehmenden Funktionsverlust. Dieser wurde auch bei einer internen Deletion oder der groben Verdopplung der Länge durch einen Epitop-tag beobachtet. Interessanterweise störte nur die kombinierte, nicht aber die einzelne Mutation der konservierten Aminosäuren D90, F94, P97 und G99 die Funktion von PEN-2. Alle funktionslosen Mutanten erlaubten zwar die PS Endoproteolyse, die PS Fragmente und PEN-2 selbst waren aber instabil und wurden durch das Proteasom abgebaut. Länge und gesamter Sequenzkontext des PEN-2 C-Terminus sind also, in der engen räumlichen Anordnung der Komplexpartner, für die Stabilisierung des PS-NTF/- CTF Heterodimers und von PEN-2 selbst im gamma-Sekretasekomplex notwendig. Die Interaktion der C-terminalen PEN-2 Mutanten mit den PS Fragmenten und den anderen beiden Komplexpartnern konnte allerdings unter Bedingungen, wo der proteasomale Abbau blockiert war, wiederhergestellt werden. Somit wurde ein Komplex aus allen vier essentiellen gamma-Sekretasekomponenten stabilisiert und isoliert, der zwar vollständig assembliert, aber noch nicht komplett gereift war. Dieser prämature Komplex zeigte noch keine gamma-Sekretaseaktivität, für welche sowohl die vollständige Assemblierung der Komponenten, als auch deren komplette Reifung essentiell sind. Zusammenfassend schlagen die vorliegenden Daten folgende Funktionen für PEN- 2 im gamma-Sekretasekomplex vor: PEN-2 wird für die Reifung des gamma-Sekretasekomplexes und die Einleitung der PS Endoproteolyse benötigt. Darüber hinaus stabilisiert PEN-2 die, durch die Endoproteolyse entstandenen PS Fragmente im Komplex. Für letztere Funktion ist ein in Länge und Gesamtsequenzkontext intakter C-Terminus wichtig, der allerdings für die Einleitung der PS Endoproteolyse nicht benötigt wird. Unabhängig von der Rolle bei der PS Endoproteolyse ist PEN-2 aber generell für die Reifung und Aktivität des gamma-Sekretasekomplexes wichtig

Accuracy of registration algorithms in subtraction CT of the lungs: A digital phantom study

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High-fat diet-induced brain region-specific phenotypic spectrum of CNS resident microglia

Diets high in fat (HFD) are known to cause an immune response in the periphery as well as the central nervous system. In peripheral adipose tissue, this immune response is primarily mediated by macrophages that are recruited to the tissue. Similarly, reactivity of microglia, the innate immune cells of the brain, has been shown to occur in the hypothalamus of mice fed a high-fat diet. To characterize the nature of the microglial response to diets high in fat in a temporal fashion, we studied the phenotypic spectrum of hypothalamic microglia of mice fed high-fat diet for 3 days and 8 weeks by assessing their tissue reaction and inflammatory signature. While we observed a significant increase in Iba1+ myeloid cells and a reaction of GFAP+ astrocytes in the hypothalamus after 8 weeks of HFD feeding, we found the hypothalamic myeloid cell reaction to be limited to endogenous microglia and not mediated by infiltrating myeloid cells. Moreover, obese humans were found to present with signs of hypothalamic gliosis and exacerbated microglia dystrophy, suggesting a targeted microglia response to diet in humans as well. Notably, the glial reaction occurring in the mouse hypothalamus was not accompanied by an increase in pro-inflammatory cytokines, but rather by an anti-inflammatory reaction. Gene expression analyses of isolated microglia not only confirmed this observation, but also revealed a downregulation of microglia genes important for sensing signals in the microenvironment. Finally, we demonstrate that long-term exposure of microglia to HFD in vivo does not impair the cell’s ability to respond to additional stimuli, like lipopolysaccharide. Taken together, our findings support the notion that microglia react to diets high in fat in a region-specific manner in rodents as well as in humans; however, this response changes over time as it is not exclusively pro-inflammatory nor does exposure to HFD prime microglia in the hypothalamus. Electronic supplementary material The online version of this article (doi:10.1007/s00401-016-1595-4) contains supplementary material, which is available to authorized users

Формы и системы оплаты труда работникам предприятия (на примере ОАО «Гомельхлебпром» филиал «Мозырский хлебозавод»)

Ligands for identifying protein aggregates are of great interest as such deposits are the pathological hallmark of a wide range of severe diseases including Alzheimers and Parkinsons disease. Here we report the synthesis of an azide functionalized fluorescent pentameric oligothiophene that can be utilized as a ligand for multimodal detection of disease-associated protein aggregates. The azide functionalization allows for attachment of the ligand to a surface by conventional click chemistry without disturbing selective interaction with protein aggregates and the oligothiophene-aggregate interaction can be detected by fluorescence or surface plasmon resonance. In addition, a methodology where the oligothiophene ligand is employed as a capturing molecule selective for aggregated proteins in combination with an antibody detecting a distinct peptide/protein is also presented. We foresee that this methodology will offer the possibility to create a variety of multiplex sensing systems for sensitive and selective detection of protein aggregates, the pathological hallmarks of several neurodegenerative diseases.Funding Agencies|Swedish Foundation for Strategic Research; Ehrling Persson Foundation; ERC Starting Independent Researcher grant (Project: MUMID)</p

A Drosophila Neurexin Is Required for Septate Junction and Blood-Nerve Barrier Formation and Function

AbstractSeptate and tight junctions are thought to seal neighboring cells together and to function as barriers between epithelial cells. We have characterized a novel member of the neurexin family, Neurexin IV (NRX), which is localized to septate junctions (SJs) of epithelial and glial cells. NRX is a transmembrane protein with a cytoplasmic domain homologous to glycophorin C, a protein required for anchoring protein 4.1 in the red blood cell. Absence of NRX results in mislocalization of Coracle, a Drosophila protein 4.1 homolog, at SJs and causes dorsal closure defects similar to those observed in coracle mutants. nrx mutant embryos are paralyzed, and electrophysiological studies indicate that the lack of NRX in glial–glial SJs causes a breakdown of the blood-brain barrier. Electron microscopy demonstrates that nrx mutants lack the ladder-like intercellular septa characteristic of pleated SJs (pSJs). These studies identify NRX as the first transmembrane protein of SJ and demonstrate a requirement for NRX in the formation of septate-junction septa and intercellular barriers

Fragile X-associated tremor ataxia syndrome with co-occurrent progressive supranuclear palsy-like neuropathology

Abstract Co-occurrence of multiple neuropathologic changes is a common phenomenon, most prominently seen in Alzheimer’s disease (AD) and Parkinson’s disease (PD), complicating clinical diagnosis and patient management. Reports of co-occurring pathological processes are emerging in the group of genetically defined repeat-associated non-AUG (RAN)-translation related diseases. Here we report a case of Fragile X-associated tremor-ataxia syndrome (FXTAS) with widespread and abundant nuclear inclusions of the RAN-translation related FMRpolyG-peptide. In addition, we describe prominent neuronal and glial tau pathology representing changes seen in progressive supranuclear palsy (PSP). The highest abundance of the respective pathological changes was seen in distinct brain regions indicating an incidental, rather than causal correlation.https://deepblue.lib.umich.edu/bitstream/2027.42/152173/1/40478_2019_Article_818.pd

Maturation of active zone assembly by Drosophila Bruchpilot

Synaptic vesicles fuse at active zone (AZ) membranes where Ca2+ channels are clustered and that are typically decorated by electron-dense projections. Recently, mutants of the Drosophila melanogaster ERC/CAST family protein Bruchpilot (BRP) were shown to lack dense projections (T-bars) and to suffer from Ca2+ channel–clustering defects. In this study, we used high resolution light microscopy, electron microscopy, and intravital imaging to analyze the function of BRP in AZ assembly. Consistent with truncated BRP variants forming shortened T-bars, we identify BRP as a direct T-bar component at the AZ center with its N terminus closer to the AZ membrane than its C terminus. In contrast, Drosophila Liprin-α, another AZ-organizing protein, precedes BRP during the assembly of newly forming AZs by several hours and surrounds the AZ center in few discrete punctae. BRP seems responsible for effectively clustering Ca2+ channels beneath the T-bar density late in a protracted AZ formation process, potentially through a direct molecular interaction with intracellular Ca2+ channel domains

Genotype–phenotype associations within the Li-Fraumeni spectrum: a report from the German Registry

Li-Fraumeni syndrome (LFS) is a cancer predisposition syndrome caused by pathogenic TP53 variants. The condition represents one of the most relevant genetic causes of cancer in children and adults due to its frequency and high cancer risk. The term Li-Fraumeni spectrum reflects the evolving phenotypic variability of the condition. Within this spectrum, patients who meet specific LFS criteria are diagnosed with LFS, while patients who do not meet these criteria are diagnosed with attenuated LFS. To explore genotype–phenotype correlations we analyzed 141 individuals from 94 families with pathogenic TP53 variants registered in the German Cancer Predisposition Syndrome Registry. Twenty-one (22%) families had attenuated LFS and 73 (78%) families met the criteria of LFS. NULL variants occurred in 32 (44%) families with LFS and in two (9.5%) families with attenuated LFS (P value < 0.01). Kato partially functional variants were present in 10 out of 53 (19%) families without childhood cancer except adrenocortical carcinoma (ACC) versus 0 out of 41 families with childhood cancer other than ACC alone (P value < 0.01). Our study suggests genotype–phenotype correlations encouraging further analyses. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13045-022-01332-1