Coherent spin relaxation in molecular magnets

Numerical modelling of coherent spin relaxation in nanomagnets, formed by magnetic molecules of high spins, is accomplished. Such a coherent spin dynamics can be realized in the presence of a resonant electric circuit coupled to the magnet. Computer simulations for a system of a large number of interacting spins is an efficient tool for studying the microscopic properties of such systems. Coherent spin relaxation is an ultrafast process, with the relaxation time that can be an order shorter than the transverse spin dephasing time. The influence of different system parameters on the relaxation process is analysed. The role of the sample geometry on the spin relaxation is investigated.Comment: Latex file, 22 pages, 7 figure

Genetic diversity of wheat (Triticum aestivum L.) plants-regenerants produced by anther culture

The study of genetic diversity of wheat (Triticum aestivum L.) plants-regenerants produced by anther culture method from hybrids involved in the Latvian wheat breeding programme was performed. Flow cytometry was used to test ploidy of 3×103 cells of each green plantregenerant, and universal retrotransposon based iPBS (inter primer binding sites) method were used to establish genetic diversity of plants-regenerants. Progenies of 13 genetically distant hybrids were involved in the study. Most of plants-regenerants have leaves with mixoploid cells. Seeds were formed only by plants-regenerants that had cells with (2n = 6x) ploidy. Majority of fertile plantsregenerants have more than 40 % of hexaploid (6x) cells. The percentage of 6x cells in plants-regenerants and diversity in cell ploidy demonstrated association with mother plant (hybrid) genotype. Percent of spontaneous diplodization was also genotype-dependent. In this experiment colchicine treatment had no significant influence on outcome of fertile plants- regenerants. New dominant allele in a hybrid plant was found in comparison with both parents what indicated possible retrotransposon moving. Genetic diversity of the plants-regenerants obtained in anther culture is a combination of parent’s allele segregation and somaclonal variation

Assessment of prognostic value GRACE and TIMI models in patients with non-st-elevation acute coronary syndrome and accompanying atrial fibrillation

Aim. То assess informative value of GRACE and TIMI scores for short-term risk stratification and treatment strategy definition in patients with NSTE-ACS and AF. Methods. The study involved 58 patients with NSTE-ACS and AF, mean age 61,8 ± 1,5 years. Risk stratification models using GRACE and TIMI scores was primary provided on AF and again after restoration of sinus rhythm or heart rate deceleration. All patients underwent coronary angiography, the groups with significant coronary lesions (group 1,34 patients) or without (group 2,24 patients) were identified. Results. At the primary risk assessment GRACE score was 185,5 ± 6,2 in group 1 and 153,3 i 6,3 in group 2 (p <0.001), high risk was observed in 97% of patients in group 1 and 66% of patients in group 2. At secondary assessment score was, respectively 153,1 ± 5,2 and 93,4 ± 4,4 (p <0.001 compared with primary in both groups), 79.1% of patients in group 2 were classified as low risk. At the primary risk assessment TIMI score was 4,1 ±0,16 in group 1 and 1,25 ± 0,16 in group 2 (p <0.001), high risk was defined only in group 1 (58.8% of patients), with 97.1 % of patients in group 2 defined low risk. At secondary assessment score in group 1 was 3,82 ± 0.16, p = 0.24, in group 2 - 0,92 ± 0,11, p <0.001. The distribution of patients in both groups according to degree of risk has not changed significantly. Conclusion. TIMI score, unlike GRACE, is informative for risk assessment in patients with NSTE-ACS and AF regardless of rhythm and heart rate.Цель. Оценка информативности моделей GRACE и TIMI для стратификации краткосрочного риска и определения стратегии лечения у пациентов с 0KC5nST и ФП. Материал и методы. Обследовано 58 пациентов с ОКСбпБТ и ФП, средний возраст 61,8 ±1.5 года. Стратификация риска с использованием моделей GRACE и TIMI проводилась первично на фоне ФП и повторно, после восстановления синусового ритма или урежения ЧСС. Всем пациентам проведена коронароангиография, выделены группы со значимым стенозирующим поражением коронарного русла (1 группа, 34 пациента) и без такового (2 группа, 24 пациента). Результаты. При первичной оценке риска по шкале GRACE число баллов составило 185,5 ± 6,2 в 1-й группе, и 153,3+6,3 во 2-й группе (р< 0,001), высокий риск отмечен у 97% пациентов 1 -й группы и 66% пациентов 2-й группы. При повторной оценке число баллов составило соответственно 153,1 ± 5,2 и 93,4 + 4.4 (р < 0,001 в сравнении с первичной оценкой в обеих группах), 79,1% пациентов 2-й группы относились к категории низкого риска. При первичной оценке риска по шкале TIMI число баллов составило 4.1 + 0.16 в 1 - й группе и 1,25 ± 0,16 во 2-й группе (р < 0,001), высокий риск определялся только в 1-й группе (58,8% пациентов), у 97.1 % пациентов 2-й группы определен низкий риск. При повторной оценке число баллов в 1 -й группе составило 3,82 ± 0,16, р = 0,24, во 2-й группе 0,92 ± 0,11, р < 0,001. Распределение пациентов обеих групп по степени риска существенно не изменилось. Выводы. Шкала TIMI, в отличие от GRACE, информативна для оценки риска при 0KC6nST и ФП независимо от ритма и ЧСС

ДИФФЕРЕНЦИАЛЬНАЯ ДИАГНОСТИКА МЕДИАСТИНАЛЬНОЙ ЛИМФАДЕНОПАТИИ ПРИ ЛИМФОМЕ И САРКОИДОЗЕ С ПОМОЩЬЮ ДИФФУЗИОННО-ВЗВЕШЕННОЙ МАГНИТНО-РЕЗОНАНСНОЙ ТОМОГРАФИИ

The aim of the study. Investigation of the potential of diffusion-weighted magnetic resonance imaging (DW-MRI) with apparent diffusion coefficient (ADC) evaluation for differential diagnosis of mediastinal lymphadenopathy in lymphoma and sarcoidosis.Materials and methods. The study included 15 patients with sarcoidosis and 7 patients with lymphoma. In each patient ADC values of 3 largest lymph nodes were measured.Results. Differences of mean ADC values in lymphoma (1,01±0,3×10-3mm2/s) and sarcoidosis (1,51±0,25×10-3mm2/s) were significant, p&lt;0,0001. Optimal cut-point value for ADC of ≤1,1×10-3mm2/s differentiated lymphoma from sarcoidosis with sensitivity of 76,2%, specificity of 97,8% and accuracy of 90,9%, the area under the ROC-curve was 0,89.Conclusion. Preliminary results of the study have demonstrated the potential of DW-MRI in differential diagnosis of lymphoma and sarcoidosis and expediency of the further study.Цель. Изучение возможностей диффузионно-взвешенной магнитно-резонансной томографии (ДВ-МРТ) грудной клетки с оценкой измеряемого коэффициента диффузии (ИКД) в дифференциальной диагностике медиастинальной лимфаденопатии при лимфоме и  саркоидозе.Материалы и методы. В исследование включены 15 пациентов с саркоидозом и 7  пациентов с лимфомой. У каждого пациента значения ИКД измерены в трех наиболее  крупных лимфатических узлах.Результаты. Выявлены значимые отличия средних значений ИКД при лимфоме (1,01±0,3×10-3 мм2/с) и саркоидозе (1,51±0,25×10-3 мм2/с), p&lt;0,0001. При использовании порогового значения ИКД ≤1,1×10-3 мм2/с чувствительность, специфичность и точность метода в дифференциальной диагностике лимфомы и саркоидоза составили 76,2; 97,8 и  90,9% соответственно, площадь под ROC-кривой — 0,89.Заключение. Предварительные результаты показали высокую информативность ДВ-МРТ в дифференциальной диагностике лимфомы и саркоидоза и целесообразность продолжения исследования

Dianthracenylazatrioxa[8]circulene: synthesis, characterization and application in OLEDs

A soluble, green-blue fluorescent, pi-extended azatrioxa[8]circulene was synthesized by oxidative condensation of a 3,6-dihydroxycarbazole and 1,4-anthraquinone by using benzofuran scaffolding. This is the first circulene to incorporate anthracene within its carbon framework. Solvent-dependent fluorescence and bright green electroluminescence accompanied by excimer emission are the key optical properties of this material. The presence of sliding pi-stacked columns in the single crystal of dianthracenylazatrioxa[8]circulene is found to cause a very high electron-hopping rate, thus making this material a promising n-type organic semiconductor with an electron mobility predicted to be around 2.26 cm(2) V-1 s(-1). The best organic light-emitting diode (OLED) device based on the dianthracenylazatrioxa[8]circulene fluorescent emitter has a brightness of around 16 000 Cd m(-2) and an external quantum efficiency of 3.3 %. Quantum dot-based OLEDs were fabricated by using dianthracenylazatrioxa[8]circulene as a host matrix material.Peer reviewe

Stability of Yellow Fever Virus under Recombinatory Pressure as Compared with Chikungunya Virus

Recombination is a mechanism whereby positive sense single stranded RNA viruses exchange segments of genetic information. Recent phylogenetic analyses of naturally occurring recombinant flaviviruses have raised concerns regarding the potential for the emergence of virulent recombinants either post-vaccination or following co-infection with two distinct wild-type viruses. To characterize the conditions and sequences that favor RNA arthropod-borne virus recombination we constructed yellow fever virus (YFV) 17D recombinant crosses containing complementary deletions in the envelope protein coding sequence. These constructs were designed to strongly favor recombination, and the detection conditions were optimized to achieve high sensitivity recovery of putative recombinants. Full length recombinant YFV 17D virus was never detected under any of the experimental conditions examined, despite achieving estimated YFV replicon co-infection levels of ∼2.4×106 in BHK-21 (vertebrate) cells and ∼1.05×105 in C710 (arthropod) cells. Additionally YFV 17D superinfection resistance was observed in vertebrate and arthropod cells harboring a primary infection with wild-type YFV Asibi strain. Furthermore recombination potential was also evaluated using similarly designed chikungunya virus (CHIKV) replicons towards validation of this strategy for recombination detection. Non-homologus recombination was observed for CHIKV within the structural gene coding sequence resulting in an in-frame duplication of capsid and E3 gene. Based on these data, it is concluded that even in the unlikely event of a high level acute co-infection of two distinct YFV genomes in an arthropod or vertebrate host, the generation of viable flavivirus recombinants is extremely unlikely

Mechanism of 2-oxoglutarate signaling by the Synechococcus elongatus PII signal transduction protein

P(II) proteins control key processes of nitrogen metabolism in bacteria, archaea, and plants in response to the central metabolites ATP, ADP, and 2-oxoglutarate (2-OG), signaling cellular energy and carbon and nitrogen abundance. This metabolic information is integrated by P(II) and transmitted to regulatory targets (key enzymes, transporters, and transcription factors), modulating their activity. In oxygenic phototrophs, the controlling enzyme of arginine synthesis, N-acetyl-glutamate kinase (NAGK), is a major P(II) target, whose activity responds to 2-OG via P(II). Here we show structures of the Synechococcus elongatus P(II) protein in complex with ATP, Mg(2+), and 2-OG, which clarify how 2-OG affects P(II)-NAGK interaction. P(II) trimers with all three sites fully occupied were obtained as well as structures with one or two 2-OG molecules per P(II) trimer. These structures identify the site of 2-OG located in the vicinity between the subunit clefts and the base of the T loop. The 2-OG is bound to a Mg(2+) ion, which is coordinated by three phosphates of ATP, and by ionic interactions with the highly conserved residues K58 and Q39 together with B- and T-loop backbone interactions. These interactions impose a unique T-loop conformation that affects the interactions with the P(II) target. Structures of P(II) trimers with one or two bound 2-OG molecules reveal the basis for anticooperative 2-OG binding and shed light on the intersubunit signaling mechanism by which P(II) senses effectors in a wide range of concentrations

A novel signal transduction protein P(II) variant from Synechococcus elongatus PCC 7942 indicates a two-step process for NAGK-P(II) complex formation

P(II) signal transduction proteins are highly conserved in bacteria, archaea and plants and have key functions in coordination of central metabolism by integrating signals from the carbon, nitrogen and energy status of the cell. In the cyanobacterium Synechococcus elongatus PCC 7942, P(II) binds ATP and 2-oxoglutarate (2-OG) in a synergistic manner, with the ATP binding sites also accepting ADP. Depending on its effector molecule binding status, P(II) (from this cyanobacterium and other oxygenic phototrophs) complexes and regulates the arginine-controlled enzyme of the cyclic ornithine pathway, N-acetyl-l-glutamate kinase (NAGK), to control arginine biosynthesis. To gain deeper insights into the process of P(II) binding to NAGK, we searched for P(II) variants with altered binding characteristics and found P(II) variants I86N and I86T to be able to bind to an NAGK variant (R233A) that was previously shown to be unable to bind wild-type P(II) protein. Analysis of interactions between these P(II) variants and wild-type NAGK as well as with the NAGK R233A variant suggested that the P(II) I86N variant was a superactive NAGK binder. To reveal the structural basis of this property, we solved the crystal structure of the P(II) I86N variant at atomic resolution. The large T-loop, which prevails in most receptor interactions of P(II) proteins, is present in a tightly bended conformation that mimics the T-loop of S. elongatus P(II) after having latched onto NAGK. Moreover, both P(II) I86 variants display a specific defect in 2-OG binding, implying a role of residue I86 in 2-OG binding. We propose a two-step model for the mechanism of P(II)-NAGK complex formation: in an initiating step, a contact between R233 of NAGK and E85 of P(II) initiates the bending of the extended T-loop of P(II), followed by a second step, where a bended T-loop deeply inserts into the NAGK clefts to form the tight complex