Retrieval of Effective Parameters of Subwavelength Periodic Photonic Structures

We revisit the standard Nicolson–Ross–Weir method of effective permittivity and permeability restoration of photonic structures for the case of subwavelength metal-dielectric multilayers. We show that the direct application of the standard method yields a false zero-epsilon point and an associated spurious permeability resonance. We show how this artifact can be worked around by the use of the cycle shift operator to the periodic multilayer in question

The international and legal framework for transregionalization of trade and economic cooperation of the BRICS countries

The emergence of a multipolar world is an integral part of the globalization processes. Strategic partnership at the regional, interregional and transregional levels is becoming a new institution and at the same time an instrument of modern international relations. The international and legal framework for the cooperation of BRICS as a transregional association is considered herein. The importance of converging the positions of the BRICS countries in the global political and economic system is emphasized. The research is aimed at the analysis of the international legal foundations of trade and economic cooperation of the BRICS countries within the system of transregional relations, factors, conditions and prospects for development. The measures to enhance and expand mutually beneficial trade and economic partnerships within the framework of BRICS will most effectively utilize their resource, technological, and trade and economic potential, creating the basis for the sustainable growth of the national economy and competitiveness in global development. The practical significance of the study lies in the analysis of the mechanisms of integration of BRICS. The results obtained may be useful in shaping the strategy of trade and economic cooperation within the framework of BRICS.peer-reviewe

Age-related features of anthropometric and biochemical status of men from infertile couples

Introduction. The obesity seems to grow into a real pandemic. As one of the consequences of obesity we observe a significant increase of infertility in married couples, including male infertility. As the situation with male fertility continues to deteriorate, we consider further investigation of etiology and pathogenesis of male infertility important. Aim of the study was to investigate age-related anthropometric characteristics and metabolic status in men from infertile couples. Material and methods. 426 men from infertile couples were divided into 5 groups according to age: 1) < 30 years old, 2) 30.0-34.9 years old, 3) 35.0-39,9 years old, 4) 40.0-44.9 years old, 5) ≥ 45 years old. We carried out anthropometric examination and biochemical blood analysis. Results. Within groups 2 to 4 we observed group-to- group consecutive increase in body weight, body mass index values, waist circumference and waist circumference to hip circumference values which are related to the increase of adipose tissue mass in the abdominal region. We also detected the increase of hyperglycemia occurrence. Higher values of the abovementioned anthropometric parameters were detected for the test subjects of the group 1 despite the younger age. We observed 60 and 40 % of upper and lower types of abdominal fat distribution respectively for the group 1 test subjects. Conclusions. Based on the anthropometric parameters we conclude that the infertility can be caused by negative influence of subcutaneous and visceral adipose tissue accumulation for the youngest test subjects (age < 30 years). For the older test subjects, infertility results of the cumulative effect of abdominal obesity and other medical and social factors. Group 4 test subjects (age 40-45) exhibit the most frequent abdominal obesity and associated with metabolic status disorders

СИНТЕЗ НОВЫХ 6-N-ЗАМЕЩЕННЫХ ПУРИНОВЫХ НУКЛЕОЗИДОВ

New derivatives of purine nucleosides containing the residues of N,N-diethylethylenediamine or N-(2-aminoethyl)pyrrolidine in 6-position of heterobase have been synthesized. The one-step preparation of 6-N-substituted nucleosides was performed in good yields by the amination of 6-Cl-derivatives of O-acetylated purine nucleosides and concomitant deacylation of OH-groups of a carbohydrate moiety with N,N-diethylethylenediamine or N-(2-aminoethyl)pyrrolidine.Осуществлен синтез новых производных пуриновых нуклеозидов, содержащих в 6-положении гетерооснования остатки N,N-диэтилэтилендиамина или N-(2-аминоэтил)пирролидина. Разработанные условия проведения реакции аминирования ряда 6-Cl-производных О-ацетилированных пуриновых нуклеозидов и сопутствующих реакций дезацилирования ОН-групп углеводного фрагмента под действием N-этилдиизопропиламина или N-(2-аминоэтил)пирролидина позволили получить деблокированные 6-N-замещенные нуклеозиды в одну стадию с хорошими выходами

The Role of Phosphatidic Acid and Cardiolipin in Stability of the Tetrameric Assembly of Potassium Channel KcsA

In this study, the roles of two anionic phospholipids—phosphatidic acid (PA), which is an important signaling molecule, and cardiolipin (CL), which plays a crucial role in the bioenergetics of the cell—in stabilizing the oligomeric structure of potassium channel KcsA were determined. The stability of KcsA was drastically increased as a function of PA or CL content (mol%) in phosphatidylcholine (PC) bilayers. Deletion of the membrane-associated N terminus significantly reduced channel stability at high levels of PA content; however, the intrinsic stability of this protein was marginally affected in the presence of CL. These studies indicate that the electrostatic-hydrogen bond switch between PA and N terminus, involving basic residues, is much stronger than the stabilizing effect of CL. Furthermore, the unique properties of the PA headgroup alter protein assembly and folding properties differently from the CL headgroup, and both lipids stabilize the tetrameric assembly via their specific interaction on the extra- or the intracellular side of KcsA

Interactions of melatonin with mammalian mitochondria. Reducer of energy capacity and amplifier of permeability transition.

Melatonin, a metabolic product of the amino acid tryptophan, induces a dose-dependent energy drop correlated with a decrease in the oxidative phosphorylation process in isolated rat liver mitochondria. This effect involves a gradual decrease in the respiratory control index and significant alterations in the state 4/state 3 transition of membrane potential (ΔΨ). Melatonin, alone, does not affect the insulating properties of the inner membrane but, in the presence of supraphysiological Ca2+, induces a ΔΨ drop and colloid-osmotic mitochondrial swelling. These events are sensitive to cyclosporin A and the inhibitors of Ca2+ transport, indicative of the induction or amplification of the mitochondrial permeability transition. This phenomenon is triggered by oxidative stress induced by melatonin and Ca2+, with the generation of hydrogen peroxide and the consequent oxidation of sulfydryl groups, glutathione and pyridine nucleotides. In addition, melatonin, again in the presence of Ca2+, can also induce substantial release of cytochrome C and AIF (apoptosis-inducing factor), thus revealing its potential as a pro-apoptotic agent

Slow Dissociation of a Charged Ligand: Analysis of the Primary Quinone QA Site of Photosynthetic Bacterial Reaction Centers

Reaction centers (RCs) are integral membrane proteins that undergo a series of electron transfer reactions during the process of photosynthesis. In the QA site of RCs from Rhodobacter sphaeroides, ubiquinone-10 is reduced, by a single electron transfer, to its semiquinone. The neutral quinone and anionic semiquinone have similar affinities, which is required for correct in situ reaction thermodynamics. A previous study showed that despite similar affinities, anionic quinones associate and dissociate from the QA site at rates ≈104 times slower than neutral quinones indicating that anionic quinones encounter larger binding barriers (Madeo, J.; Gunner, M. R. Modeling binding kinetics at the QA site in bacterial reaction centers. Biochemistry2005, 44, 10994–11004). The present study investigates these barriers computationally, using steered molecular dynamics (SMD) to model the unbinding of neutral ground state ubiquinone (UQ) and its reduced anionic semiquinone (SQ–) from the QA site. In agreement with experiment, the SMD unbinding barrier for SQ– is larger than for UQ. Multi Conformational Continuum Electrostatics (MCCE), used here to calculate the binding energy, shows that SQ– and UQ have comparable affinities. In the QA site, there are stronger binding interactions for SQ– compared to UQ, especially electrostatic attraction to a bound non-heme Fe2+. These interactions compensate for the higher SQ– desolvation penalty, allowing both redox states to have similar affinities. These additional interactions also increase the dissociation barrier for SQ– relative to UQ. Thus, the slower SQ– dissociation rate is a direct physical consequence of the additional binding interactions required to achieve a QA site affinity similar to that of UQ. By a similar mechanism, the slower association rate is caused by stronger interactions between SQ– and the polar solvent. Thus, stronger interactions for both the unbound and bound states of charged and highly polar ligands can slow their binding kinetics without a conformational gate. Implications of this for other systems are discussed