The mechanism of caesium intercalation of graphene

Properties of many layered materials, including copper- and iron-based superconductors, topological insulators, graphite and epitaxial graphene can be manipulated by inclusion of different atomic and molecular species between the layers via a process known as intercalation. For example, intercalation in graphite can lead to superconductivity and is crucial in the working cycle of modern batteries and supercapacitors. Intercalation involves complex diffusion processes along and across the layers, but the microscopic mechanisms and dynamics of these processes are not well understood. Here we report on a novel mechanism for intercalation and entrapment of alkali-atoms under epitaxial graphene. We find that the intercalation is adjusted by the van der Waals interaction, with the dynamics governed by defects anchored to graphene wrinkles. Our findings are relevant for the future design and application of graphene-based nano-structures. Similar mechanisms can also play a role for intercalation of layered materials.Comment: 8 pages, 7 figures in published form, supplementary information availabl

Intrinsic and extrinsic corrugation of monolayer graphene deposited on SiO2

Using scanning tunneling microscopy (STM) in ultra high vacuum and atomic force microscopy, we investigate the corrugation of graphene flakes deposited by exfoliation on a Si/SiO2 (300 nm) surface. While the corrugation on SiO2 is long-range with a correlation length of about 25 nm, some of the graphene monolayers exhibit an additional corrugation with a preferential wave length of about 15 nm. A detailed analysis shows that the long range corrugation of the substrate is also visible on graphene, but with a reduced amplitude, leading to the conclusion that the graphene is partly freely suspended between hills of the substrate. Thus, the intrinsic rippling observed previously on artificially suspended graphene can exist as well, if graphene is deposited on SiO2.Comment: 10 pages, 11 figures, including supplementary materia

Cardiac myosin binding protein-C plays no regulatory role in skeletal muscle structure and function

Myosin binding protein-C (MyBP-C) exists in three major isoforms: slow skeletal, fast skeletal, and cardiac. While cardiac MyBP-C (cMyBP-C) expression is restricted to the heart in the adult, it is transiently expressed in neonatal stages of some skeletal muscles. However, it is unclear whether this expression is necessary for the proper development and function of skeletal muscle. Our aim was to determine whether the absence of cMyBP-C alters the structure, function, or MyBP-C isoform expression in adult skeletal muscle using a cMyBP-C null mouse model (cMyBP-C((t/t))). Slow MyBP-C was expressed in both slow and fast skeletal muscles, whereas fast MyBP-C was mostly restricted to fast skeletal muscles. Expression of these isoforms was unaffected in skeletal muscle from cMyBP-C((t/t)) mice. Slow and fast skeletal muscles in cMyBP-C((t/t)) mice showed no histological or ultrastructural changes in comparison to the wild-type control. In addition, slow muscle twitch, tetanus tension, and susceptibility to injury were all similar to the wild-type controls. Interestingly, fMyBP-C expression was significantly increased in the cMyBP-C((t/t)) hearts undergoing severe dilated cardiomyopathy, though this does not seem to prevent dysfunction. Additionally, expression of both slow and fast isoforms was increased in myopathic skeletal muscles. Our data demonstrate that i) MyBP-C isoforms are differentially regulated in both cardiac and skeletal muscles, ii) cMyBP-C is dispensable for the development of skeletal muscle with no functional or structural consequences in the adult myocyte, and iii) skeletal isoforms can transcomplement in the heart in the absence of cMyBP-C

Wearable devices can predict the outcome of standardized 6-minute walk tests in heart disease

Wrist-worn devices with heart rate monitoring have become increasingly popular. Although current guidelines advise to consider clinical symptoms and exercise tolerance during decision-making in heart disease, it remains unknown to which extent wearables can help to determine such functional capacity measures. In clinical settings, the 6-minute walk test has become a standardized diagnostic and prognostic marker. We aimed to explore, whether 6-minute walk distances can be predicted by wrist-worn devices in patients with different stages of mitral and aortic valve disease. A total of n = 107 sensor datasets with 1,019,748 min of recordings were analysed. Based on heart rate recordings and literature information, activity levels were determined and compared to results from a 6-minute walk test. The percentage of time spent in moderate activity was a predictor for the achievement of gender, age and body mass index-specific 6-minute walk distances (p < 0.001; R2 = 0.48). The uncertainty of these predictions is demonstrated

Discovery of Tantalum, Rhenium, Osmium, and Iridium Isotopes

Currently, thirty-eight tantalum, thirty-eight rhenium, thirty-nine osmium, and thirty-eight iridium, isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.Comment: To be published in At. Data Nucl. Data Table

Widespread Epigenetic Abnormalities Suggest a Broad DNA Methylation Erasure Defect in Abnormal Human Sperm

Male-factor infertility is a common condition, and etiology is unknown for a high proportion of cases. Abnormal epigenetic programming of the germline is proposed as a possible mechanism compromising spermatogenesis of some men currently diagnosed with idiopathic infertility. During germ cell maturation and gametogenesis, cells of the germ line undergo extensive epigenetic reprogramming. This process involves widespread erasure of somatic-like patterns of DNA methylation followed by establishment of sex-specific patterns by de novo DNA methylation. Incomplete reprogramming of the male germ line could, in theory, result in both altered sperm DNA methylation and compromised spermatogenesis.We determined concentration, motility and morphology of sperm in semen samples collected by male members of couples attending an infertility clinic. Using MethyLight and Illumina assays we measured methylation of DNA isolated from purified sperm from the same samples. Methylation at numerous sequences was elevated in DNA from poor quality sperm.This is the first report of a broad epigenetic defect associated with abnormal semen parameters. Our results suggest that the underlying mechanism for these epigenetic changes may be improper erasure of DNA methylation during epigenetic reprogramming of the male germ line

SnoRNA Snord116 (Pwcr1/MBII-85) Deletion Causes Growth Deficiency and Hyperphagia in Mice

Prader-Willi syndrome (PWS) is the leading genetic cause of obesity. After initial severe hypotonia, PWS children become hyperphagic and morbidly obese, if intake is not restricted. Short stature with abnormal growth hormone secretion, hypogonadism, cognitive impairment, anxiety and behavior problems are other features. PWS is caused by lack of expression of imprinted genes in a ∼4 mb region of chromosome band 15q11.2. Our previous translocation studies predicted a major role for the C/D box small nucleolar RNA cluster SNORD116 (PWCR1/HBII-85) in PWS. To test this hypothesis, we created a ∼150 kb deletion of the >40 copies of Snord116 (Pwcr1/MBII-85) in C57BL/6 mice. Snord116del mice with paternally derived deletion lack expression of this snoRNA. They have early-onset postnatal growth deficiency, but normal fertility and lifespan. While pituitary structure and somatotrophs are normal, liver Igf1 mRNA is decreased. In cognitive and behavior tests, Snord116del mice are deficient in motor learning and have increased anxiety. Around three months of age, they develop hyperphagia, but stay lean on regular and high-fat diet. On reduced caloric intake, Snord116del mice maintain their weight better than wild-type littermates, excluding increased energy requirement as a cause of hyperphagia. Normal compensatory feeding after fasting, and ability to maintain body temperature in the cold indicate normal energy homeostasis regulation. Metabolic chamber studies reveal that Snord116del mice maintain energy homeostasis by altered fuel usage. Prolonged mealtime and increased circulating ghrelin indicate a defect in meal termination mechanism. Snord116del mice, the first snoRNA deletion animal model, reveal a novel role for a non-coding RNA in growth and feeding regulation

Indirect exclusion of four candidate genes for generalized progressive retinal atrophy in several breeds of dogs

BACKGROUND: Generalized progressive retinal atrophy (gPRA) is a hereditary ocular disorder with progressive photoreceptor degeneration in dogs. Four retina-specific genes, ATP binding cassette transporter retina (ABCA4), connexin 36 (CX36), c-mer tyrosin kinase receptor (MERTK) and photoreceptor cell retinol dehydrogenase (RDH12) were investigated in order to identify mutations leading to autosomal recessive (ar) gPRA in 29 breeds of dogs. RESULTS: Mutation screening was performed initially by PCR and single strand conformation polymorphism (SSCP) analysis, representing a simple method with comparatively high reliability for identification of sequence variations in many samples. Conspicuous banding patterns were analyzed via sequence analyses in order to detect the underlying nucleotide variations. No pathogenetically relevant mutations were detected in the genes ABCA4, CX36, MERTK and RDH12 in 71 affected dogs of 29 breeds. Yet 30 new sequence variations were identified, both, in the coding regions and intronic sequences. Many of the sequence variations were in heterozygous state in affected dogs. CONCLUSION: Based on the ar transmittance of gPRA in the breeds investigated, informative sequence variations provide evidence allowing indirect exclusion of pathogenetic mutations in the genes ABCA4 (for 9 breeds), CX36 (for 12 breeds), MERTK (for all 29 breeds) and RDH12 (for 9 breeds)

An Unexpected Function of the Prader-Willi Syndrome Imprinting Center in Maternal Imprinting in Mice

Genomic imprinting is a phenomenon that some genes are expressed differentially according to the parent of origin. Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are neurobehavioral disorders caused by deficiency of imprinted gene expression from paternal and maternal chromosome 15q11–q13, respectively. Imprinted genes at the PWS/AS domain are regulated through a bipartite imprinting center, the PWS-IC and AS-IC. The PWS-IC activates paternal-specific gene expression and is responsible for the paternal imprint, whereas the AS-IC functions in the maternal imprint by allele-specific repression of the PWS-IC to prevent the paternal imprinting program. Although mouse chromosome 7C has a conserved PWS/AS imprinted domain, the mouse equivalent of the human AS-IC element has not yet been identified. Here, we suggest another dimension that the PWS-IC also functions in maternal imprinting by negatively regulating the paternally expressed imprinted genes in mice, in contrast to its known function as a positive regulator for paternal-specific gene expression. Using a mouse model carrying a 4.8-kb deletion at the PWS-IC, we demonstrated that maternal transmission of the PWS-IC deletion resulted in a maternal imprinting defect with activation of the paternally expressed imprinted genes and decreased expression of the maternally expressed imprinted gene on the maternal chromosome, accompanied by alteration of the maternal epigenotype toward a paternal state spread over the PWS/AS domain. The functional significance of this acquired paternal pattern of gene expression was demonstrated by the ability to complement PWS phenotypes by maternal inheritance of the PWS-IC deletion, which is in stark contrast to paternal inheritance of the PWS-IC deletion that resulted in the PWS phenotypes. Importantly, low levels of expression of the paternally expressed imprinted genes are sufficient to rescue postnatal lethality and growth retardation in two PWS mouse models. These findings open the opportunity for a novel approach to the treatment of PWS

Imprinting regulates mammalian snoRNA-encoding chromatin decondensation and neuronal nucleolar size

Imprinting, non-coding RNA and chromatin organization are modes of epigenetic regulation that modulate gene expression and are necessary for mammalian neurodevelopment. The only two known mammalian clusters of genes encoding small nucleolar RNAs (snoRNAs), SNRPN through UBE3A(15q11–q13/7qC) and GTL2(14q32.2/12qF1), are neuronally expressed, localized to imprinted loci and involved in at least five neurodevelopmental disorders. Deficiency of the paternal 15q11–q13 snoRNA HBII-85 locus is necessary to cause the neurodevelopmental disorder Prader–Willi syndrome (PWS). Here we show epigenetically regulated chromatin decondensation at snoRNA clusters in human and mouse brain. An 8-fold allele-specific decondensation of snoRNA chromatin was developmentally regulated specifically in maturing neurons, correlating with HBII-85 nucleolar accumulation and increased nucleolar size. Reciprocal mouse models revealed a genetic and epigenetic requirement of the 35 kb imprinting center (IC) at the Snrpn–Ube3a locus for transcriptionally regulated chromatin decondensation. PWS human brain and IC deletion mouse Purkinje neurons showed significantly decreased nucleolar size, demonstrating the essential role of the 15q11–q13 HBII-85 locus in neuronal nucleolar maturation. These results are relevant to understanding the molecular pathogenesis of multiple human neurodevelopmental disorders, including PWS and some causes of autism