Effect of Cr spacer on structural and magnetic properties of Fe/Gd multilayers

In this work we analyse the role of a thin Cr spacer between Fe and Gd layers on structure and magnetic properties of a [Fe(35A)/Cr(tCr)/Gd(50A)/Cr(tCr)]x12 superlattice. Samples without the Cr spacer (tCr=0) and with a thin tCr=4A are investigated using X-ray diffraction, polarized neutron and resonance X-ray magnetic reflectometry, SQUID magnetometery, magneto-optical Kerr effect and ferromagnetic resonance techniques. Magnetic properties are studied experimentally in a wide temperature range 4-300K and analysed theoretically using numerical simulation on the basis of the mean-field model. We show that a reasonable agreement with the experimental data can be obtained considering temperature dependence of the effective field parameter in gadolinium layers. The analysis of the experimental data shows that besides a strong reduction of the antiferromagnetic coupling between Fe and Gd, the introduction of Cr spacers into Fe/Gd superlattice leads to modification of both structural and magnetic characteristics of the ferromagnetic layers

Bacterial formate dehydrogenase. Increasing the enzyme thermal stability by hydrophobization of alpha-helices

AbstractNAD+-dependent formate dehydrogenase (EC 1.2.1.2, FDH) from methylotrophic bacterium Pseudomonas sp.101 exhibits the highest stability among the similar type enzymes studied. To obtain further increase in the thermal stability of FDH we used one of general approaches based on hydrophobization of protein α-helices. Five serine residues in positions 131, 160, 168, 184 and 228 were selected for mutagenesis on the basis of (i) comparative studies of nine FDH amino acid sequences from different sources and (ii) with the analysis of the ternary structure of the enzyme from Pseudomonas sp.101. Residues Ser-131 and Ser-160 were replaced by Ala, Val and Leu. Residues Ser-168, Ser-184 and Ser-228 were changed into Ala. Only Ser/Ala mutations in positions 131, 160, 184 and 228 resulted in an increase of the FDH stability. Mutant S168A was 1.7 times less stable than the wild-type FDH. Double mutants S(131,160)A and S(184,228)A and the four-point mutant S(131,160,184,228)A were also prepared and studied. All FDH mutants with a positive stabilization effect had the same kinetic parameters as wild-type enzyme. Depending on the position of the replaced residue, the single point mutation Ser/Ala increased the FDH stability by 5–24%. Combination of mutations shows near additive effect of each mutation to the total FDH stabilization. Four-point mutant S(131,160,184,228)A FDH had 1.5 times higher thermal stability compared to the wild-type enzyme

Magnetoresistive study of antiferromagnetic--weak ferromagnetic transition in single-crystal La2_{2}CuO4+δ_{4+\delta}

The resistive measurements were made to study the magnetic field-induced antiferromagnetic (AF) - weak ferromagnetic (WF) transition in La$_2$CuO$_4$ single-crystal. The magnetic field (DC or pulsed) was applied normally to the CuO$_2$ layers. The transition manifested itself in a drastic decrease of the resistance in critical fields of ~5-7 T. The study is the first to display the effect of the AF -WF transition on the conductivity of the La$_2$CuO$_4$ single-crystal in the parallel - to - CuO$_2$ layers direction. The results provide support for the 3-dimensional nature of the hopping conduction of this layered oxide.Comment: 8 pages, 7 figures, RevTe

Comparative characteristics of inducible NO synthase inhibitor and nitric oxide donor in endothelial dysfunction correction caused by osteoarthrosis under experimental conditions

Study have been carried out on white Wistar line rats (age – 3 months, weight – 180-220 g). According to the tasks the animals were divided into 7 groups. 1st group is intact (n = 20). 2nd group is rats, which were modeled osteoarthritis without further correction and were withdrawn from the experiment in the first stage (7th day) (n=40). 3rd group is rats, which were modeled osteoarthritis without further correction and removed from the experiment in the second stage (21st day) (n=40). 4th group is rats, in which experimental osteoarthritis was corrected with nonsteroidal anti-inflammatory drugs (NSAIDs) (Diclofenac) and aminoguanidine and removed from the experiment in the first stage (7th day) (n=20). 5th group is rats, in which experimental osteoarthritis was corrected with NSAIDs (Diclofenac) and aminoguanidine and withdrawn from the experiment in the second stage (21st day) (n=20). 6th group is rats, where experimental osteoarthritis was corrected using NSAIDs and a 7% L-arginine solution and withdrawn from the experiment in the first stage (7th day) (n=20). 7th group is rats, in which experimental osteoarthritis was corrected with NSAIDs and 7% L-arginine solution and withdrawn from the experiment in the second stage (21st day) (n=20) Animals were withdrawn from the experiment for the 7th day and the 21st day after the simulation of the pathological condition. NSAIDs (Diclofenac), aminoguanidine and L-arginine were administered from the beginning of the study. We have obtained the following results: The increase in the content of von Willebrand factor (VWF) in the animals blood proves that endothelial dysfunction is an important part of experimental osteoarthritis pathogenesis. It’s revealed the tendency which directed on normalization of the endothelial dysfunction investigated marker at correction by aminoguadine as a part of complex therapy. L-arginine involvement in the complex correction in experimental osteoarthritis more pronouncedly normalized the VWF level, which indicates the endothelial function normalization. The use of nitric oxide donor is more effective in comparison with the inhibition of inducible NO synthase also in the endothelial nitric oxide synthase activity analysis

Risk of breast cancer and other cancers in heterozygotes for ataxia-telangiectasia

Mortality from cancer among 178 parents and 236 grandparents of 95 British patients with ataxia-telangiectasia was examined. For neither parents nor grandparents was mortality from all causes or from cancer appreciably elevated over that of the national population. Among mothers, three deaths from breast cancer gave rise to a standardized mortality ratio of 3.37 (95% confidence interval (CI): 0.69–9.84). In contrast, there was no excess of breast cancer in grandmothers, the standardized mortality ratio being 0.89 (95% CI: 0.18–2.59), based on three deaths. This is the largest study of families of ataxia-telangiectasia patients conducted in Britain but, nonetheless, the study is small and CIs are wide. However, taken together with data from other countries, an increased risk of breast cancer among female heterozygotes is still apparent, though lower than previously thought. © 1999 Cancer Research Campaig

Revisiting the Indus Basin Model for an energy sustainable Pakistan

Water is vital and an essential entity directly and indirectly for all living creatures from their birth, whereas electrical energy has a dominant role in the growth of society in general and for human beings in particular. Optimal use of water and production of electrical energy at minimum cost are potential research challenges. Hydraulic energy is one of the cheapest and the most exploited renewable energy resource for power generation worldwide, and is in line with the seventh United Nations Sustainable Development Goal (SDG 7). The Indus basin is a trans-boundary basin, and its modeling has been a source of interest for scientists and policymakers. Indus Basin Model Revised (IBMR) has many variants, all focusing on optimal use of water for irrigation purposes. In this paper, the modified IBMR model is proposed addressing both agriculture and power generation aspects simultaneously. This model optimizes the Consumer Producer Surplus (CPS) by considering different water inflow probabilities. A parameter has been introduced in the modified objective function to manipulate the supply of water to agriculture and hydropower generation. The proposed model has been implemented in Generic Algebraic Modeling System (GAMS) and case studies have been investigated in presence and absence of power generation. The results obtained show that, with incorporation of hydropower, basin wide income is increased up to 11.83% using 50% exceedance probability, and results are in agreement with reference power generation estimated by National Transmission and Dispatch Company (NTDC). The SDG 7 targets ensure the reasonable, dependable, sustainable and contemporary energy access to all. The current research is focusing on how Pakistan would achieve the SDG 7 targets. By 2040, it is anticipated that Pakistan’s energy mix will have around 40% of hydropower and 16% of renewable energy

Structural characterization of human Vaccinia-Related Kinases (VRK) bound to small-molecule inhibitors identifies different P-loop conformations

The human genome encodes two active Vaccinia-related protein kinases (VRK), VRK1 and VRK2. These proteins have been implicated in a number of cellular processes and linked to a variety of tumors. However, understanding the cellular role of VRKs and establishing their potential use as targets for therapeutic intervention has been limited by the lack of tool compounds that can specifically modulate the activity of these kinases in cells. Here we identified BI-D1870, a dihydropteridine inhibitor of RSK kinases, as a promising starting point for the development of chemical probes targeting the active VRKs. We solved co-crystal structures of both VRK1 and VRK2 bound to BI-D1870 and of VRK1 bound to two broad-spectrum inhibitors. These structures revealed that both VRKs can adopt a P-loop folded conformation, which is stabilized by different mechanisms on each protein. Based on these structures, we suggest modifications to the dihydropteridine scaffold that can be explored to produce potent and specific inhibitors towards VRK1 and VRK2