Title Stabilization of Membrane Pores by Packing

We present a model for pore stabilization in membranes without surface tension. Whereas an isolated pore is always unstable (since it either shrinks tending to re-seal or grows without bound til to membrane disintegration), it is shown that excluded volume interactions in a system of many pores can stabilize individual pores of a given size in a certain range of model parameters. For such a multipore membrane system, the distribution of pore size and associated pore lifetime are calculated within the mean field approximation. We predict that, above certain temperature when the effective line tension becomes negative, the membrane exhibits a dynamic sieve-like porous structure.Comment: 4 pages, 4 figure

Physical and chemical processes and the morphofunctional characteristics of human erythrocytes in hyperglycaemia

Background: This study examines the effect of graduated hyperglycaemia on the state and oxygen-binding ability of hemoglobin, the correlation of phospholipid fractions and their metabolites in the membrane, the activity of proteolytic enzymes and the morphofunctional state of erythrocytes. Methods: Conformational changes in the molecule of hemoglobin were determined by Raman spectroscopy. The structure of the erythrocytes was analyzed using laser interference microscopy (LIM). To determine the activity of NADN-methemoglobinreductase, we used the P.G. Board method. The degree of glycosylation of the erythrocyte membranes was determined using a method previously described by Felkoren et al. Lipid extraction was performed using the Bligh and Dyer method. Detection of the phospholipids was performed using V. E. Vaskovsky method. Results: Conditions of hyperglycaemia are characterized by a low affinity of hemoglobin to oxygen, which is manifested as a parallel decrease in the content of hemoglobin oxyform and the growth of deoxyform, methemoglobin and membrane-bound hemoglobin. The degree of glycosylation of membrane proteins and hemoglobin is high. For example, in the case of hyperglycaemia, erythrocytic membranes reduce the content of all phospholipid fractions with a simultaneous increase in lysoforms, free fatty acids and the diacylglycerol (DAG). Step wise hyperglycaemia in incubation medium and human erythrocytes results in an increased content of peptide components and general trypsin-like activity in the cytosol, with a simultaneous decreased activity of µ-calpain and caspase 3. Conclusions: Metabolic disorders and damage of cell membranes during hyperglycaemia cause an increase in the population of echinocytes and spherocytes. The resulting disorders are accompanied with a high probability of intravascular haemolysis.</p

Осмотический демиелинизирующий синдром

ABSTRACT. This article discusses the clinical cases of rare and difficult to diagnose brain damage — osmotic demyelinating syndrome (ODS). ODS is a lifethreatening condition, manifested by acute demyelination of the headbrain on the background of water-electrolyte disturbances,usually associated with fast management of hyponatremia. Within the framework of ODS, central pontine myelinolysis (CPM) and extra-pontine myelinolysis (EPM) are observed, which are accompanied by acute demyelination in the pons and white matter of the cerebral hemispheres, respectively. In 60%, CPM combine with EPM. The main reason for the development of ODS is a violation of water-electrolyte metabolism associated with alcohol abuse, chronic hepatic and/or renal failure, diabetes mellitus, Sheehan syndrome, polydipsia, condition after the removal of pituitary adenoma, bulimia, immunodeficiency syndrome. Today, the diagnosis of ODS is based on magnetic resonance imaging of the brain. The article indicates the main causes of the disease, clinical features, methods of diagnosis and treatment, as well as the outcomes of the disease.РЕЗЮМЕ. Данная статья посвящена обсуждению клинических случаев редкого и трудно диагностируемого поражения головного мозга — осмотического демиелинизирующего синдрома (ОДС). ОДС — жизнеугрожающее состояние, проявляющееся остро возникающей демиелинизацией головного мозга на фоне водно-электролитных нарушений, как правило, связанных с быстрой коррекцией гипонатриемии. В рамках ОДС выделяют центральный понтинный миелинолиз (ЦПМ) и экстрапонтинный миелинолиз (ЭПМ), которые сопровождаются острой демиелинизацией в области моста и белого вещества больших полушарий головного мозга соответственно. В 60% ОДС сочетает в себе ЦПМ и ЭПМ. Основная причина развития ОДС — нарушения водно-электролитного обмена, возникающие на фоне злоупотребления алкоголем, хронической печеночной и/или почечной недостаточности, сахарного диабета, синдрома Шихана, полидипсии, состояния после удаления аденомы гипофиза, булимии, синдрома иммунодефицита. В настоящее время диагнос- тика ОДС основана на данных магнитно-резонансной томографии головного мозга. В статье ука- заны основные причины заболевания, клинические особенности, методы диагностики и лечения, а также исходы заболевания

PEG Branched Polymer for Functionalization of Nanomaterials with Ultralong Blood Circulation

Nanomaterials have been actively pursued for biological and medical applications in recent years. Here, we report the synthesis of several new poly(ethylene glycol) grafted branched-polymers for functionalization of various nanomaterials including carbon nanotubes, gold nanoparticles (NP) and gold nanorods (NRs), affording high aqueous solubility and stability for these materials. We synthesize different surfactant polymers based upon poly-(g-glutamic acid) (gPGA) and poly(maleic anhydride-alt-1-octadecene) (PMHC18). We use the abundant free carboxylic acid groups of gPGA for attaching lipophilic species such as pyrene or phospholipid, which bind to nanomaterials via robust physisorption. Additionally, the remaining carboxylic acids on gPGA or the amine-reactive anhydrides of PMHC18 are then PEGylated, providing extended hydrophilic groups, affording polymeric amphiphiles. We show that single-walled carbon nanotubes (SWNTs), Au NPs and NRs functionalized by the polymers exhibit high stability in aqueous solutions at different pHs, at elevated temperatures and in serum. Morever, the polymer-coated SWNTs exhibit remarkably long blood circulation (t1/2 22.1 h) upon intravenous injection into mice, far exceeding the previous record of 5.4 h. The ultra-long blood circulation time suggests greatly delayed clearance of nanomaterials by the reticuloendothelial system (RES) of mice, a highly desired property for in vivo applications of nanomaterials, including imaging and drug delivery

Disentangling the sources of ionizing radiation in superconducting qubits

Radioactivity was recently discovered as a source of decoherence and correlated errors for the real-world implementation of superconducting quantum processors. In this work, we measure levels of radioactivity present in a typical laboratory environment (from muons, neutrons, and γ-rays emitted by naturally occurring radioactive isotopes) and in the most commonly used materials for the assembly and operation of state-of-the-art superconducting qubits. We present a GEANT-4 based simulation to predict the rate of impacts and the amount of energy released in a qubit chip from each of the mentioned sources. We finally propose mitigation strategies for the operation of next-generation qubits in a radio-pure environment

Disentangling the sources of ionizing radiation in superconducting qubits

Radioactivity was recently discovered as a source of decoherence and correlated errors for the real-world implementation of superconducting quantum processors. In this work, we measure levels of radioactivity present in a typical laboratory environment (from muons, neutrons, and gamma's emitted by naturally occurring radioactive isotopes) and in the most commonly used materials for the assembly and operation of state-of-the-art superconducting qubits. We develop a GEANT-4 based simulation to predict the rate of impacts and the amount of energy released in a qubit chip from each of the mentioned sources. We finally propose mitigation strategies for the operation of next-generation qubits in a radio-pure environment