Specific features of the electronic, spin, and atomic structures of a topological insulator Bi2Te2.4Se0.6

The specific features of the electronic and spin structures of a triple topological insulator Bi2Te2.4Se0.6, which is characterized by high-efficiency thermoelectric properties, have been studied with the use of angular- and spin-resolved photoelectron spectroscopy and compared with theoretical calculations in the framework of the density functional theory. It has been shown that the Fermi level for Bi2Te2.4Se0.6 falls outside the band gap and traverses the topological surface state (the Dirac cone). Theoretical calculations of the electronic structure of the surface have demonstrated that the character of distribution of Se atoms on the Te–Se sublattice practically does not influence the dispersion of the surface topological electronic state. The spin structure of this state is characterized by helical spin polarization. Analysis of the Bi2Te2.4Se0.6 surface by scanning tunnel microscopy has revealed atomic smoothness of the surface of a sample cleaved in an ultrahigh vacuum, with a lattice constant of ~4.23 Å. Stability of the Dirac cone of the Bi2Te2.4Se0.6 compound to deposition of a Pt monolayer on the surface is shown.This study was supported by the Ministry of Education and Science of the Russian Federation, the St. Petersburg State University (project nos. 11.38.271.2014 and 15.61.202.2015), and the Russian Foundation for Basic Research (project nos. 12-02-00226, 13-02-91327, 14-08-31110, and 13-02-12110). The research was also performed at the Resource Center “Physical Methods of Surface Investigation” at St. Petersburg State University. We are also grateful to collaborators of the Helmholtz-Zentrum (Berlin) for financial and technical support.Peer reviewe

Clinical, hormonal and molecular-genetic characteristics of monogenic diabetes mellitus associated with the mutations in the <i>INS</i> gene

Background: Currently more than 50 mutations of the INS gene are known to affect the various stages of insulin biosynthesis in the beta cells of the pancreas. However only individual cases of diabetes mellitus (DM) associated with heterozygous mutations in the coding region of the INS gene were reported in Russian Federation. We report a group of patients with a clinical manifestation of DM caused by mutations in both coding and non-coding regions of the INS gene. The patients with a mutation in the intron of the INS gene are reported for the first time in Russian FederationMaterials and methods: 60 patients with an isolated course of neonatal DM (NDM), 52 patients with a manifestation of DM at the age of 7–12 months and the absence of the main autoimmune markers of type 1 DM, 650 patients with the MODY phenotype were included in the study. NGS technology was used for molecular genetic research. Author’s panel of primers (Custom DNA Panel) was used for multiplex PCR and sequencing using Ion Ampliseq™ technology. The author’s panel “­Diabetes Mellitus” included 28 genes (13 candidate genes of MODY and other genes associated with DM).Results: 13 heterozygous mutations were identified in 16 probands and 9 relatives. The majority of mutations were detected in patients with PNDM (18.75%) and in patients with an onset of DM at the age of 7–12 months (9.6%). Mutations in the INS gene were detected in 2 patients (0.3%) in the group with the MODY phenotype. Mutations in the INS gene were not detected in patients with transient NDM (TNDM). Analysis of clinical data in patients with PND and onset of diabetes at the age of 7–12 months did not show significant differences in the course of the disease. The clinical characteristics of the cases of MODY10 and diabetes caused by a mutation in the intron of the INS gene are reported in details.Conclusion: The role of INS gene mutations in NDM, MODY, and DM with an onset at the age of 7–12 months was analyzed in a large group of patients. The clinical characteristics of DM due to a mutation in the intron of the INS gene are reported for the first time in the Russian Federation

Nontrivial spin structure of graphene on Pt(111) at the Fermi level due to spin-dependent hybridization

The electronic and spin structure of a graphene monolayer synthesized on Pt(111) has been investigated experimentally by angle- and spin-resolved photoemission with different polarizations of incident synchrotron radiation and using density functional theory calculations. It is shown that despite the observed total quasifreestanding character of the dispersion of the graphene π state remarkable local distortions and breaks in the dispersions take place due to hybridization between the graphene π and Pt d states. Corresponding spin-dependent avoided-crossing effects lead to significant modification of the spin structure and cause an enhanced induced spin-orbit splitting of the graphene π states near the Fermi level in the region of the K¯ point of the graphene Brillouin zone (BZ) with a magnitude of 80-200 meV depending on the direction in the BZ. Using p, s, and elliptical polarizations of the synchrotron radiation, the contributions of the graphene π and Pt d states were separated and their intersection at the Fermi level, which is important for effective spin injection between these states, was shown. Moreover, analysis of the data allows us to conclude that in the region of the Dirac point the spin structure of the system cannot be described by a Rashba splitting, and even a spin-orbit gap between lower and upper Dirac cones is observed.The work was partially supported by a grant of Saint Petersburg State University for scientific investigations (Grant No. 11.38.271.2014) and Russian Foundation for Basic Research (RFBR) projects (Project No. 13-02-91327) and performed within the framework of collaboration between the Deutsche Forschungsgemeinschaft and Russian Foundation for Basic Research (Grant No. RA 1041/3-1). We acknowledge the financial support of the University of Basque Country UPV/EHU (Grant No. GIC07-IT-756-13), the Departamento de Educacion del Gobierno Vasco and the Spanish Ministerio de Ciencia e Innovacion (Grant No. FIS2010-19609-C02-01), Project FIS2013-48286-C2-1-P of the Spanish Ministry of Economy and Competitiveness MINECO, and the Tomsk State University Competitiveness Improvement Program.Peer Reviewe

Estimation of cytoprotective effect of bismuth tripotassium dicitrate on gastric mucosa at <i>H. pylori</i> eradication and long-term drug intake

Aim of investigation. To identify cellular «target» of bismuth tripotassium dicitrate (De-nol) therapy – DNA protection of generative zone cells of stomach mucosa (SM) from damages by oxidative burst products in neutrophilic leukocytes at continued intake of the drug for 4 wks after the ending of eradication therapy.Material and methods. Overall 53 patients after successful eradication therapy for chronic H. pyloriassociated gastritis were investigated: in 28 of them De-nol treatment was continued, 25 were included to the group of comparison. At control upper GI endoscopy biopsy samples were taken from 5 SM points according to OLGA-system protocol. In biopsy specimens presence of neutrophilic infiltration was estimated in mucosal generative zones exclusively. Borders of a generative zone were determined by the presence of myofibroblasts surrounding glandular epithelium which were identified immunohistochemically, using smooth-muscle actin as a marker. Cells with damaged DNA were revealed by immunehistochemical detection of Р53 protein.Results. No correlation between neutrophilic infiltration of SM and р53-positive cells quantity in generative zone (–0,14≤r≤0,08) was revealed in both groups. Comparison of cumulative scores of P53 label in generative zones epithelium after treatment demonstrated no significant difference between groups. Only at comparison of P53 expression level in each sampling point statistically significant differences before and after treatment (Wilcoxon W-matched-pairs ranks criterion) have been found only in group of patients who continued treatment.Conclusions. Detection of the damaged DNA in SM generative zone cells by immunehistochemical assay of P53-positive cells allows to establish significant decrease of their number in biopsies of the patients, who received the drug after cessation of eradication therapy that can be considered as a marker of protective effect for generative zone cells — cytoprotective «target» of bismuth drug

Co-regulation of IFNG and IFNGR1 at the genomic level

Η ανάπτυξη του ανοσοποιητικού συστήματος και η ανοσολογική απάντηση του ξενιστή στις μικροβιακές μολύνσεις βασίζονται στη μεταγραφική ενεργοποίηση και τη σίγηση ποικίλων γονιδίων. Χρησιμοποιώντας το σύστημα των άωρων CD4+ Τ, ΤΗ1 και ΤΗ2 λεμφοκυττάρων, εστιαστήκαμε στη μελέτη της μεταγραφικής ρύθμισης των γενετικών τόπων της Ιντερφερόνης-γ (Ifnγ, χρωμόσωμα ποντικού 10) και του υποδοχέα 1 της ιντερφερόνης-γ (IfnγR1, χρωμόσωμα ποντικού 10). Στην παρούσα διδακτορική διατριβή παρουσιάζουμε ένα μοντέλο μονοαλληλικής ενδοχρωμοσωμικής αλληλεπίδρασης ανάμεσα στο γενετικό τόπο της Ifnγ και αυτό του IfnγR1 στα κύτταρα όπου εκφράζεται ο υποδοχέας, δηλαδή τα άωρα CD4+ λεμφοκύτταρα. Ο έλεγχος της έκφρασης των γονιδίων Ifnγ και IfnγR1 στο επίπεδο του ενός κυττάρου φανέρωσε τη λειτουργική σημασία της αλληλεπίδρασης, αφού ο IfnγR1 εκφράζεται στα άωρα και τα TH1 κύτταρα κυρίως από το ένα αλληλόμορφο, το οποίο και συνεντοπίζεται με αυτό της Ifnγ. Οι αλληλεπιδράσεις προτείνεται ότι λαμβάνουν χώρα σε μεταγραφικά εργοστάσια, αλλά παρόλα αυτά είναι ανεξάρτητες της μεταγραφής. Τέλος, φαίνεται ότι η φυσική γειτνίαση πραγματοποιείται με τη συμμετοχή του γενικού πρωτεϊνικού παράγοντα ρύθμισης της πυρηνικής αρχιτεκτονικής CTCF, που στρατολογείται πιθανότατα μέσω του T-bet στο μη-μεθυλιωμένο αλληλόμορφο του υποδοχέα.The development of the immune system and the host immune response to microbial infections rely on the transcriptional activation and silencing of multiple gene loci. By utilizing the differentiation system of naive CD4+, TH1 and TH2 lymphocytes, we focused on the transcriptional regulation of the interferon-γ (Ifnγ, mouse choromosome 10) and interferon-γ receptor 1 (IfnγR1, mouse chromosome 10) genes. So, in the present doctoral thesis we present a model whereby there are long range monoallelic intra-chromosomal associations between the IfnγR1 and Ifnγ loci, in cell types that express the receptor. Expression profile analysis revealed the functional significance of the co-localization, since IfnγR1 is expressed in naive CD4+ and TH1 cells from the allele that is in close physical proximity with the Ifnγ locus. Moreover, the interactions take place in transcription factories, but they are independent of transcription. Importantly, CTCF, a general transcription factor, seems to play a critical role to the aforementioned phenomena. Regarding the functional characterization of the underlying mechanism, here we provide evidence to support the hypothesis that CTCF is recruited to the non-methylated promoter region of IfnγR1 allele, possibly with the help of Τ-bet and sets a pattern of monoallelic co-localization and positive transcriptional regulation of the receptor gene locus